ALBERT

Description: 〈p〉Publication date: 1 January 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, Volume 438〈/p〉 〈p〉Author(s): T. Kubley, F. Naab, O. Toader, G. Was〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The Michigan Ion Beam Laboratory (MIBL) at the University of Michigan houses three electrostatic accelerators and six ion sources, providing beams to five target chambers and a TEM via nine distinct beamlines. Such a large system incorporates numerous control and monitoring instruments that can more easily be managed through a digital remote interface system. MIBL has implemented a variety of standard laboratory hardware and custom alternative hardware and software tools into a remote interface system that provides for greater laboratory efficiency, increased application flexibility and information flow and reduced cost. The outcome is that users can operate three accelerators and their corresponding beamline system from one console using a master control program, eliminating the need to constantly traverse the facility to monitor and manipulate instruments. Furthermore, the digitalization and centralization of the data generated by each subsystem has allowed for logging and variable correlation that would otherwise be impossible at such a large scale, and enabled the future application of modern tools such as machine learning to enhance operational efficiency.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 December 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, Volume 436〈/p〉 〈p〉Author(s): Juliette Colombani, Ahmedou Sidi, Jean-François Larché, Agnès Rivaton〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The effect of gamma-irradiation and temperature to accelerate, in a representative way, the ageing of EVA (Ethylene Vinyl Acetate)/EPDM (Ethylene Propylene Diene Monomer) blends was investigated. These blends constitute model materials of cable insulation used in Nuclear Power Plants (NPPs). Physicochemical evolutions of the blends were monitored by InfraRed (IR) spectroscopy, gel fraction measurements and Differential Scanning Calorimetry (DSC). After having pointed out the main similarities between the thermooxidative degradation (100 °C) and the radiooxidative degradation at room temperature, both stresses were combined to accelerate the ageing. It is shown that combining gamma-irradiation and high temperature, or subsequent thermooxidation after radiooxidation, accelerates the ageing but may cause distortion within the degradation mechanisms. These limitations of representativeness encountered are particularly due to an increase in chain scission reactions and formation of new crystallites in the blend.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 December 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, Volume 436〈/p〉 〈p〉Author(s): Anatoly Balagurov, Dmitry Balagurov, Ivan Bobrikov, Andrey Bogdzel, Vladimir Drozdov, Andrey Kirilov, Vladimir Kruglov, Sergey Kulikov, Svetlana Murashkevich, Valentin Prikhodko, Vasily Shvetsov, Valery Simkin, Alexander Sirotin, Nikolay Zernin, Valery Zhuravlev〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The High Resolution Fourier Diffractometer (HRFD) is a neutron time-of-flight spectrometer with a fast Fourier chopper and a correlation mode of data acquisition designed to study atomic and magnetic structures of crystalline materials with high resolution in reciprocal space. The HRFD was constructed in the early 1990s by a collaboration of JINR (Dubna), PNPI (Gatchina) and VTT (Espoo) and began operating routinely in 1994 at the IBR-2 pulsed reactor in Dubna. If correlation analysis is used, the HRFD Δ〈em〉d〈/em〉/〈em〉d〈/em〉 resolution is determined by the maximum rotational speed of the Fourier chopper. For 〈em〉V〈/em〉〈sub〉max〈/sub〉 = 6000 rpm, “high-resolution” patterns are measured by backscattering detectors with Δ〈em〉d〈/em〉/〈em〉d〈/em〉 ≈ 0.0015 despite a very short flight path (〈em〉L〈/em〉 ≈ 20 m) between chopper and sample. Switching to a regular TOF-mode (without Fourier chopper) makes HRFD one of the world’s best high-intensity diffractometers, capable of measuring diffraction patterns in the range of ∼1 min and less. In this paper, the experience of using HRFD at IBR-2 is considered and a possible solution for some technical and methodical problems of Fourier diffractometry at a long-pulse neutron source recognized during its operation is discussed. New possibilities appearing after the recent substantial HRFD upgrade and further perspectives on the method are also presented.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 December 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, Volume 436〈/p〉 〈p〉Author(s): Felix S. Olise, Adedamola D. Aladese, Chinonso E. Ugwumadu〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉L-shell ionisation and x-ray production cross sections of trans-uranium elements: Np, Pu and Am, induced by protons of energies 5.00–20.00 MeV, have been calculated. The cross sections for the targets were obtained using computer codes based on the ECPSSR theory. Due to the lack of experimental data of the targets considered, in view of their radioactive, toxic and unstable nature, the calculated cross sections were subsequently validated. This was achieved using the computer codes to evaluate the ionisation and x-ray production cross sections of Uranium induced by protons of energies in the 1.00–20.00 MeV range. This study also showed that the relative x-ray line intensities associated with the ionisation and x-ray productions of the targets considered are dependent on protons energies.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 November 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, Volume 434〈/p〉 〈p〉Author(s): Shen Yang, Zuoxing Guo, Min Zhang, Qingfeng Guan, Yunxue Jin, Yuhua Liu〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The microstructure and electrochemical behavior of zircaloy-4 prior and after high-current pulsed electron beam (HCPEB) irradiation were investigated. The microstructures of the surface layer were studied by means of X-ray diffraction (XRD), optical microscopy (OM), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Observation results indicated that, martensitic phase transformation was induced by HCPEB irradiation and formed plate martensitic structures containing a high density of ultrafine twins. When the number of pulse was increased, these structures were constantly refined along with their parent β grains. Besides, second-phase particles (SPPs) in the modified layers were completely dissolved into the substrate and formed Fe, Cr-containing supersaturated solid solution. The electrochemical behavior was characterized by using electrode impedance spectroscopy (EIS) and potentiodynamic polarization curves. Electrochemical results demonstrated that, compared to the initial specimen, all the irradiated specimens showed better corrosion resistance in 0.01 mol LiOH solution, among which 25-pulsed specimen possessed the best corrosion resistance. Surface selective purification, supersaturated Fe, Cr elements in substrate and abundant structure defects jointly promoted the improvement of the corrosion resistance.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 January 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, Volume 438〈/p〉 〈p〉Author(s): Gunther Korschinek, Thomas Faestermann〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The experiments searching in solar system bodies for freshly produced radionuclides from outside the solar system are reviewed, with a special focus on accelerator mass spectrometry. A surplus of 〈sup〉60〈/sup〉Fe has been found at eight locations in terrestrial oceans as well as in lunar samples. This surplus is attributed to supernova activity within 300 light years from the Sun about 1.5 to 3.0 Ma ago. An intensive search for the r-process nuclide 〈sup〉244〈/sup〉Pu in deep-ocean material yielded an upper limit far below the expectation if it were produced exclusively by core-collapse supernovae. Thus, a much less frequent stellar event than core-collapse supernovae must be the site where the heaviest nuclides are produced.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 December 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, Volume 436〈/p〉 〈p〉Author(s): Zhimei Yang, Fan Lan, Yun Li, Min Gong, Mingmin Huang, Bo Gao, Junkui Hu, Yao Ma〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The effects of the atomic migration between metal and semiconductor by swift heavy ion (SHI) irradiation on the turn on voltage (V〈sub〉on〈/sub〉), ideality factor (〈em〉n〈/em〉) and Schottky barrier height (SBH) in 4H-SiC Schottky barrier diodes (SBD) have been researched. The results show that the 〈em〉n〈/em〉 decreases and SBH increases for 4H-SiC SBDs without irradiation and with 5 × 10〈sup〉9〈/sup〉 ions/cm〈sup〉2〈/sup〉 at increasing testing temperature. After irradiation, the V〈sub〉on〈/sub〉 and SBH of the sample increases due to the forming of higher barrier height TiSi〈sub〉x〈/sub〉 by annealing treatment at 873 K. The SHI and annealing treatment can make the deep level defect to be partly recovered. The results may be explained that the interfacial structure was modified due to the silicon and carbon atomic migration during SHI process at the interfacial region between metal and semiconductor, and then reacting at high temperature annealing treatment.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 December 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, Volume 436〈/p〉 〈p〉Author(s): Xingguo Feng, Kaifeng Zhang, Yugang Zheng, Hui Zhou, Zhihua Wan〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Cr-Zr-N films were deposited in a DC magnetron sputtering system with Cr and Zr targets under the mixed Ar and N〈sub〉2〈/sub〉 gases. The effect of the Zr content on structure, morphology, hardness and tribological behavior of Cr-Zr-N films were systematically investigated. The XRD result showed that all the Cr-Zr-N films exhibited FCC structure. FESEM indicated that the morphologies of the film changed from particular surface feature with a faceted polygon to granular-like structure as the Zr content increased. Nano-indentation results exhibited that with an increase of the Zr content in the films, the hardness and elastic modulus linearly increased and reached maximum values of 27.1 GPa and 350.5 GPa at a Zr content of 20.8 at.%. Tribological test results indicated that the wear rate decreases remarkably from 3.2 × 10〈sup〉−14〈/sup〉 m〈sup〉3〈/sup〉/Nm to 0.98 × 10〈sup〉−14〈/sup〉 m〈sup〉3〈/sup〉/Nm with increasing Zr content in the films from 1.0 at.% to 20.8 at.%.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: Available online 28 September 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms〈/p〉 〈p〉Author(s): Luis A. Marqués, María Aboy, Iván Santos, Pedro López, Fuccio Cristiano, Antonino La Magna, Karim Huet, Toshiyuki Tabata, Lourdes Pelaz〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉We combine focused experiments with molecular dynamics simulations to investigate in detail the formation of {0 0 1} loops in nanosecond laser-annealed silicon. We demonstrate that at temperatures close to the melting point, self-interstitial rich silicon is driven into dense liquid-like droplets that are highly mobile within the solid crystalline matrix. These liquid droplets grow by a coalescence mechanism and eventually transform into {0 0 1} loops through a liquid-to-solid phase transition in the nanosecond timescale.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: Available online 18 September 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms〈/p〉 〈p〉Author(s): Wataru Kada, Ivan Sudić, Natko Skukan, Shunsuke Kawabata, Takahiro Satoh, Junichi Susaki, Suzuya Yamada, Takahiro Sekine, Raj Kumar Parajuli, Makoto Sakai, Kenta Miura, Masashi Koka, Naoto Yamada, Tomihiro Kamiya, Milko Jakšić, Osamu Hanaizumi〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Two different types of SiAlON phosphors, namely, α-SiAlON:Eu and β-SiAlON:Eu, that have been developed as scintillators are evaluated for their luminescent properties by ion-beam-induced luminescence (IBIL) analysis under 2–3-MeV H〈sup〉+〈/sup〉-microbeam irradiation. The IBIL spectra show that both α-SiAlON:Eu and β-SiAlON:Eu have bright luminescence similar to that of ZnS:Ag scintillators. The α-SiAlON:Eu and β-SiAlON:Eu IBIL spectra have peaks at wavelengths of 605 and 540 nm, respectively, which lie in the preferred range of general optical sensors. As the irradiation progresses, the IBIL intensity of conventional ZnS:Ag scintillators decreases sharply, whereas that of the two SiAlONs remains largely unchanged. Moreover, the thermal resistivity of β-SiAlON:Eu is measured by IBIL under temperature control. The IBIL intensity retains half of its original value at the highest temperature of 773 K. The present experimental results reveal the two different types of SiAlON to be potential candidates for a scintillation monitoring tool for harsh environments in which intense beam irradiation at high temperature can be expected.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: Available online 3 September 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms〈/p〉 〈p〉Author(s): M. Roumie, I. Oggiano, A. Reslan, A. Srour, Z. El-Morr, M. Castiglione, M. Tabbal, M. Korek, B. Nsouli〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The study the ancient Phoenician cult place of Kharayeb, in the rural hinterland of Tyre, southern of Lebanon, dated to the Iron Age and Hellenistic periods is particularly helpful in evaluating the complexity and variability of the so called “Hellenism” and of “Greek cultural influences” in the Phoenician world. The PIXE analytical technique was used to characterize the elemental composition of several artefacts from this archaeological site, mainly figurines and some artisanal objects, with an attempt to analyze geological samples that could be potential clay sources in the area. Furthermore, the PIXE information about the composition of the studied objects helped to understand if the figurines were locally produced or imported from the coast and how was the process of production connected to the sanctuary. Hence, particle induced X-ray emission technique PIXE was used to determine the elemental composition of about 57 excavated fragments of figurines and pottery from Kharayeb site, as well as from two another archaeological sites, Jemjim and Tyre which is the prestigious city of antiquity, located on the eastern Mediterranean coast. Then, PIXE analyses with multivariate statistical methods were used to compare and to reveal characteristic groups. Finally, PIXE technique contributed to establish a first database of chemical composition of Phoenician pottery, which will broaden the existing database currently related only to archaeological pottery from coastal sites in Lebanon. Therefore, this work will probably be used for any future archaeological study on Phoenician pottery in the Phoenician colonies in the Mediterranean basin.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 November 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, Volume 434〈/p〉 〈p〉Author(s): Sergei Ghyngazov, Sergey Pavlov, Valeria Kostenko, Anatoly Surzhikov〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The modification effects of the subsurface layers of alumina ceramics under irradiation by high-power carbon beam are investigated. Irradiation was performed on TEMP ion beam accelerator at a residual pressure of 10〈sup〉−4〈/sup〉 Torr. The energy of accelerated ions was 200 keV. The current density per pulse varied within 15–85 A/cm〈sup〉2〈/sup〉. Mechanical properties and phase composition in subsurface ceramics layers before and after irradiation were analyzed by microhardness testing and X-ray diffraction, respectively. No changes in the ceramics phase composition were observed. It was found that the treatment of ceramics with a powerful pulsed ion beam leads to a significant change in the microhardness of subsurface layers. The increase in microhardness depends on the current density and the deposited energy. The greatest increase in microhardness (up to 2.5 times) is observed at a current density of 50 A/cm〈sup〉2〈/sup〉.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 November 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, Volume 434〈/p〉 〈p〉Author(s): Vanaraj Solanki, D. Kabiraj, D.K. Avasthi, Shikha Varma〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The topographic evaluation of the nano-scale pattern, on ZnO (001) surface, and its scaling properties have been investigated here after low energy atom beam irradiation. Preferential sputtering promotes the formation of Zn-rich zones near the surface that serve as the nucleation centers for the spontaneous nanostructure growth. The rms roughness (〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si1.gif" overflow="scroll"〉〈mrow〉〈mi〉σ〈/mi〉〈/mrow〉〈/math〉) however increases with irradiation fluence and displays power law behaviour, 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si4.gif" overflow="scroll"〉〈mrow〉〈mi〉σ〈/mi〉〈mo〉∼〈/mo〉〈msup〉〈mrow〉〈mtext〉t〈/mtext〉〈/mrow〉〈mrow〉〈mi〉β〈/mi〉〈/mrow〉〈/msup〉〈/mrow〉〈/math〉, for 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si5.gif" overflow="scroll"〉〈mrow〉〈mtext〉t〈/mtext〉〈mo〉〈〈/mo〉〈msub〉〈mrow〉〈mtext〉t〈/mtext〉〈/mrow〉〈mrow〉〈mi〉c〈/mi〉〈/mrow〉〈/msub〉〈/mrow〉〈/math〉 (crossover time) but saturates at longer time scale. In the case of 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si6.gif" overflow="scroll"〉〈mrow〉〈mtext〉t〈/mtext〉〈mo〉〉〈/mo〉〈msub〉〈mrow〉〈mtext〉t〈/mtext〉〈/mrow〉〈mrow〉〈mi〉c〈/mi〉〈/mrow〉〈/msub〉〈/mrow〉〈/math〉, 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si1.gif" overflow="scroll"〉〈mrow〉〈mi〉σ〈/mi〉〈/mrow〉〈/math〉 is independent of irradiation time but interestingly follows the power law behaviour 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si8.gif" overflow="scroll"〉〈mrow〉〈mi〉σ〈/mi〉〈mo〉∼〈/mo〉〈msup〉〈mrow〉〈mtext〉L〈/mtext〉〈/mrow〉〈mrow〉〈mi〉α〈/mi〉〈/mrow〉〈/msup〉〈/mrow〉〈/math〉, where L is the size of image used in analysis. The morphology of the surfaces has also been investigated using the height-height correlation and power spectral density methods. The observed values of growth (〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si9.gif" overflow="scroll"〉〈mrow〉〈mi〉β〈/mi〉〈/mrow〉〈/math〉) and roughness (〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si10.gif" overflow="scroll"〉〈mrow〉〈mi〉α〈/mi〉〈/mrow〉〈/math〉) exponents indicate a scaling behavior that is induced by the disordered but well-defined geometry of the nanostructures.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 December 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, Volume 436〈/p〉 〈p〉Author(s): Congyu Hao, Xiangyan Li, Yange Zhang, Yichun Xu, Yan Jiang, C.S. Liu, Q.F. Fang, Xianping Wang, Tao Zhang〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Neutrons induce displacement damage to the tungsten-based plasma facing material by creating radiation-defects, e.g., vacancies (Vs) and self-interstitial atoms (SIAs). These defects will accumulate on the surface and further affect surface's role as defect sinks. In this work, by combining molecular statics (MS) and object kinetic Monte Carlo (OKMC) methods, we study the clustering of the V/SIA on the two typical low-index W surfaces (1 0 0) and (1 1 0) to uncover the effect of the agglomerated surface V/SIA on the segregation and annihilation of the V and SIA nearby. Results show that the V〈sub〉n〈/sub〉/SIA〈sub〉n〈/sub〉 could form on the two surfaces via the agglomeration of the V/SIA on the surfaces with the energy release and the reduced energy barrier for the V/SIA diffusion near the V〈sub〉n〈/sub〉/SIA〈sub〉n〈/sub〉 as respective energetic and kinetic driving force. Yet, the V〈sub〉n〈/sub〉/SIA〈sub〉n〈/sub〉 is more easily formed on surface (1 1 0) compared to surface (1 0 0) due to the much larger binding energy of a V with a V〈sub〉n〈/sub〉 (or a SIA with a SIA〈sub〉n〈/sub〉) and lower diffusion energy barrier of the V/SIA on surface (1 1 0) than that on surface (1 0 0). Long-term OKMC simulations of the V/SIA behavior near the surfaces at 1000 K show that surface (1 0 0) could develop to locally convex structures due to the SIA agglomeration, while surface (1 1 0) will evolve to locally concave-convex structures due to the V/SIA clustering. Meanwhile, the interaction mechanism of the V/SIA with the surface is changed from the fundamental segregation, annihilation and clustering of the V/SIA near a pure surface to the trapping for the V/SIA by the locally concave-convex structure and the junction.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 December 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, Volume 436〈/p〉 〈p〉Author(s): Vladimir Epp, Julia Janz, Margarita Zotova〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉We study theoretically the angular momentum of radiation emitted at axial channeling of the fast particles in a crystal or in a bunch of micro- or nanotubes placed in strong magnetic field. It is shown that high energy particles channeled in the presence of magnetic field are effective source of vortex radiation in the X-ray and gamma-range of photons energies. We show that there are two factors that increase the angular momentum of emitted radiation in the presence of magnetic field. First, the magnetic field favours additional “twisting” of the channeled particles in a certain direction and, secondly, the particles that have the corresponding initial angular momentum are predominantly captured into the channeling mode. Dependence of the angular momentum of radiation on the value of magnetic field and on the incident angle is studied.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: Available online 12 September 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms〈/p〉 〈p〉Author(s): J. Botsoa, T. Sauvage, B. Courtois, D. De Sousa Meneses, M.F. Barthe〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Nuclear reaction analysis (NRA) has been used for the determination of nitrogen content in diamond by monitoring the 〈sup〉14〈/sup〉N(d,p〈sub〉0〈/sub〉)〈sup〉15〈/sup〉N nuclear reaction from a 1.4 MeV deuteron beam incident on the diamond samples. Results obtained in bulk diamond are compared to those inferred from infrared optical transmission measurements. Furthermore, nitrogen content has also been measured by NRA in diamond nanoparticles and in the light of these results we evaluate the conversion of nitrogen to nitrogen-vacancy (NV) complexes in both bulk diamond and diamond nanoparticles after a 2.4 MeV-proton irradiation and subsequent thermal annealing.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 December 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, Volume 436〈/p〉 〈p〉Author(s): Xin Yang, Xiangguo Zeng, Liang Chen, Yang Guo, Huayan Chen, Fang Wang〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Atom-scale numerical calculations were performed to investigate the damage behavior in close-packed hexagonal zirconium (HCP-Zr) by primary irradiation through a molecular dynamics (MD) study. The influences of Primary Knock-on Atom (PKA) energy (〈em〉E〈/em〉〈sub〉PKA〈/sub〉), the PKA incident direction and the ambient temperature (〈em〉T〈/em〉) on the cascade collision were studied comprehensively. The results show that the athermal recombination corrected displacements per atom (arc-dpa) model is more accurate in comparison with the Norgett-Robinson-Torrens (NRT) model when predicting the steady vacancy (〈em〉N〈/em〉〈sub〉s〈/sub〉). It was found that the vacancy peak (〈em〉N〈/em〉〈sub〉peak〈/sub〉), the peak time (〈em〉t〈/em〉〈sub〉peak〈/sub〉), and the steady time (〈em〉t〈/em〉〈sub〉s〈/sub〉) increase as 〈em〉E〈/em〉〈sub〉PKA〈/sub〉 and 〈em〉T〈/em〉 increase. The steady vacancy also increases with the increase of 〈em〉E〈/em〉〈sub〉PKA〈/sub〉. It was also found that 〈em〉N〈/em〉〈sub〉s〈/sub〉 increases and subsequently decreases by increasing 〈em〉T〈/em〉, suggesting that there is a suitable temperature to maximize 〈em〉N〈/em〉〈sub〉s〈/sub〉 when 〈em〉E〈/em〉〈sub〉PKA〈/sub〉 is constant. In addition, it was discovered that the PKA incident direction has little effect on vacancy dynamic history. It was proved that 〈em〉E〈/em〉〈sub〉PKA〈/sub〉 can worsen the irradiation damage in crystal Zr, but 〈em〉T〈/em〉 can relieve such damage. In addition, the incident direction was found to have an insignificant effect on the damage. This study highlights that the steady vacancy concentration (〈em〉C〈/em〉) can characterize the material irradiation damage.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 December 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, Volume 436〈/p〉 〈p〉Author(s): Lihu Yang, Vladyslav Rayda, Xiaolei Zhao, Sarah Murseli, Xianfang Song, Ian D. Clark〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉This paper describes a technique of making carbonate by rapid CO〈sub〉2〈/sub〉 capture from groundwater for direct measurement of the 〈sup〉14〈/sup〉C content by accelerator mass spectrometry (AMS). The DIC in groundwater was extracted from acidified water in the form of carbon dioxide (CO〈sub〉2〈/sub〉), and transferred into saturated barium hydroxide solution to form barium carbonate (BaCO〈sub〉3〈/sub〉). After the BaCO〈sub〉3〈/sub〉 precipitate was freeze-dried, it was mixed with a metal powder and pressed into an AMS target for measurement. The behaviors of Si, Al, Fe and Ta powder as the binder with carbonate were evaluated. The C〈sup〉3+〈/sup〉 currents from carbonate targets mixed with Fe or Ta were found generally larger than those with Si or Al by a factor of two. The baked Ta was shown to produce fewer contaminating 〈sup〉14〈/sup〉C counts than all the others, with or without baking. The CaCO〈sub〉3〈/sub〉/Ta and BaCO〈sub〉3〈/sub〉/Ta mass mixing ratios in the range from 1:2 to 1:4 and in 1:1.5, respectively, produced optimized currents. The precision and accuracy of the measurement by direct CaCO〈sub〉3〈/sub〉 or BaCO〈sub〉3〈/sub〉 sputtering using Ta as the binder, were evaluated in comparison to a selected reference material. The agreement was reasonably good between the direct carbonate measurement and the high precision measurement through combustion and graphitization. These findings support the further development of a rapid assessment method directly from field work to measurement.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 December 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, Volume 436〈/p〉 〈p〉Author(s): Qing Huang, Hui Tang〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉One IG-110 graphite sample was irradiated with 2 MeV Xe〈sup〉20+〈/sup〉 ions to a fluence of 2.4 × 10〈sup〉15〈/sup〉 ions/cm〈sup〉2〈/sup〉. Then the irradiated sample and one un-irradiated sample were tested in molten Li〈sub〉2〈/sub〉BeF〈sub〉4〈/sub〉 salt at a pressure of 0.3 MPa for 20 h, in order to investigate irradiation’s effects on graphite-Li〈sub〉2〈/sub〉BeF〈sub〉4〈/sub〉 salt compatibility. For both samples, the intruded salt have round surfaces and spherical salt particles with sizes 〈2 μm were shown on samples’ surface, indicating that irradiation did not change the non-wettability of Li〈sub〉2〈/sub〉BeF〈sub〉4〈/sub〉 salt to graphite. Besides, testing in molten Li〈sub〉2〈/sub〉BeF〈sub〉4〈/sub〉 salt did not have obvious effects on graphite’s surface morphology and Raman peaks, indicating that chemical attack did not happen to irradiated graphite. Therefore, irradiated graphite has a great structural stability in molten Li〈sub〉2〈/sub〉BeF〈sub〉4〈/sub〉 salt.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: Available online 25 September 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms〈/p〉 〈p〉Author(s): Jin-Hua Zhao, Han-Xu Zhang, Li-Li Ye, Guang-Tong Guo, Jing Guan〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Sodium doped Calcium Barium Niobate (Na:CBN) is of potential use in integrated optical devices with high-power laser operation because of its unique nonlinear optical properties and the high Curie temperature. In our work, we research the fabrication and properties of planar Na:CBN waveguide by multiple energy He ion implantation. The sample is implanted with (450 + 500 + 550) keV He ions at room temperature with fluence of (3 + 3 + 3) × 10〈sup〉16〈/sup〉 ions/cm〈sup〉2〈/sup〉. Prism-coupling and end-face coupling measurements are used to investigate the optical properties of ion-implanted Na:CBN crystal. SRIM and FD-BPM simulations have been used to study the damage formation and light propagation process on the Na:CBN waveguide. Micro-Raman imaging is a powerful nondestructive approach to examine lattice modification and local micro-structural change. We perform confocal micro-Raman measurement, which is used to provide the information about the crystal structure of Na:CBN crystal after multiple energy He ion implantation. This work could provide useful information for integrated optical device based on Na:CBN crystal.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 December 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, Volume 436〈/p〉 〈p〉Author(s): S.N. Menon, B.S. Dhabekar, Sonal Kadam, D.K. Koul〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Lithium magnesium phosphate (LiMgPO〈sub〉4〈/sub〉) based phosphors have been found to be quite promising for optically stimulated luminescence (OSL) dosimetry. These phosphors have unique characteristic of linearity over a range of nine orders of magnitude of dose. However, the thermally stimulated luminescence (TL) and OSL signals of these phosphors fade with time. This constraint has limited the applicability of this phosphor in dosimetric application. This paper attempts to understand the cause and nature of fading. This paper also reports the synthesise of a new LiMgPO〈sub〉4〈/sub〉 based phosphor with less fading.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: Available online 11 September 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms〈/p〉 〈p〉Author(s): Tomoaki. Nishimura, Takeshi Kasai, Tomonori Mishima, Kazuo Kuriyama, Tohru Nakamura〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉We investigated the conditions of sample preparation for obtaining low contact resistance to Al/Ti electrode on n-GaN fabricated by Si implantation and analyzed its interface structure. In conditions of sample preparation showing the lowest resistance, we found that there is an AlN layer and not the generally believed TiN layer on the interface between the electrode and the GaN substrate. Silicon was implanted into GaN followed by annealing at 1200 °C to investigate the effects of surface carrier concentration on ohmic contact. Layers of Ti and Al were then deposited and annealed at 550–800 °C. In the sample annealed at 600 °C with a relatively high fluence of 5 × 10〈sup〉14〈/sup〉 atoms/cm〈sup〉2〈/sup〉, the sample displayed the lowest contact resistance of 1.2 × 10〈sup〉−7〈/sup〉 Ωcm〈sup〉2〈/sup〉. This indicates that the formation of a high concentration of impurities on the GaN surface, resulting from Si implantation effectively reduced the contact resistance of the Al/Ti electrode. Ti and Al were also deposited on un-implanted GaN substrates, and the resulting multilayer electrodes with different Al/Ti ratios were annealed at 550–900 °C to investigate the electrode structure and the detail structure of metal/semiconductor interface. The film compositions and the interfacial microstructures of the samples were analyzed by the Rutherford backscattering spectroscopy method, optical microscopy, high-resolution scanning electron microscopy (STEM), energy-dispersive X-ray spectroscopy (EDX), and electron energy loss spectroscopy (EELS). For samples with Al/Ti ratios of ∼4.2, the under part of electrode became rich in Al at annealing temperatures of 550–600 °C. On the basis of the STEM and EELS analysis, Ti was not present at immediately above the GaN substrate interface, whereas AlN (thickness = 1–2 nm) was present. The RBS-determined total amount of Ga was 5 × 10〈sup〉15〈/sup〉 atoms/cm〈sup〉2〈/sup〉, which corresponds to the amount of Ga in 1.1 nm of the GaN layer that is probably replaced by the AlN layer.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 December 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, Volume 436〈/p〉 〈p〉Author(s): F. Ditrói, S. Takács, H. Haba, Y. Komori, M. Aikawa, M. Saito, T. Murata〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Natural silver targets have been irradiated by using a 50 MeV alpha-particle beam in order to measure the activation cross sections of radioisotopes in the 40–50 MeV energy range. Among the radio-products there are medically important isotopes such as 〈sup〉110m〈/sup〉In and 〈sup〉111〈/sup〉In. For optimizing the production of these radioisotopes and regarding their purity and specific activity the cross section data for every produced radioisotope are important. New data are measured in this energy range and the results of some previous measurements have been confirmed. Physical yield curves have been calculated by using the new cross section data completed with the results from the literature.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: Available online 6 September 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms〈/p〉 〈p〉Author(s): Sou Watanabe, Yuya Katai, Haruaki Matsuura, Wataru Kada, Masashi Koka, Takahiro Satoh, Tsuyoshi Arai〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉IBIL and EXAFS analyses were carried out on an adsorbent impregnating CMPO and HDEHP extractants for the extraction chromatography technology in order to evaluate chemical structure of complex formed in the adsorbent. EXAFS analysis suggested that contributions of CMPO and HDEHP for Eu(III) extraction must be not only individual ones but also cooperative. IBIL spectra obtained for the adsorbent were attributed to complexes of Eu(III) with organic compounds, and the profile was sensitive to coordination structure of the organic compounds. Those analytical technologies were shown to be effective to investigate chemical environment of cation charged in organic compounds. Two dimensional imaging using specific luminescence was also tried on the adsorbent, and required performance for the system to evaluate distribution of the complexes inside the particle was clarified.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 December 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, Volume 436〈/p〉 〈p〉Author(s): Q.M. Xu, Z.H. Yang, Y.P. Guo, Y.H. Chen, X.M. Zhou, H.P. Liu, H.Y. Zhao〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉This paper reports the measurement of visible light emission in the collisions of slow (〈em〉V〈/em〉 ∼ 0.38 〈em〉V〈/em〉〈sub〉Bohr〈/sub〉) highly charged Xe〈sup〉q+〈/sup〉 (6 ≤ q ≤ 23) ions with GaAs surface. The experimental results include Ga I lines from the 4d 〈sup〉2〈/sup〉D〈sub〉3/2〈/sub〉 and 5 s 〈sup〉2〈/sup〉S〈sub〉1/2〈/sub〉 to the 4p 〈sup〉2〈/sup〉P〈sub〉1/2,3/2〈/sub〉 states and Ga II lines belonged to the electron transitions 4p〈sup〉2〈/sup〉〈sup〉1〈/sup〉D〈sup〉2〈/sup〉 → 4s4p 〈sup〉1〈/sup〉P〈sub〉1〈/sub〉, 4s5s 〈sup〉1〈/sup〉S〈sub〉0〈/sub〉 → 4s4p 〈sup〉1〈/sup〉P〈sub〉1〈/sub〉 and 4s4f 〈sup〉1〈/sup〉F〈sub〉3〈/sub〉 → 4s4d 〈sup〉3〈/sup〉D〈sub〉3〈/sub〉. The measurement on the projectile charge state dependences of Ga II at 270.20, 277.90, 426.20 nm and Ga I at 287.65, 294.55, 403.55, 417.35 nm lines is presented. It is concluded that the photon yields increase with charge state in the same way as the potential energy increases and the potential energy is the driving force for optical emission of excited Ga atoms and Ga〈sup〉+〈/sup〉 ions.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 December 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, Volume 436〈/p〉 〈p〉Author(s): Meenakshi Singh, M.R. Singh, Anjali Sharma, Bhushan Dighe〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The discrimination of medieval silver coins into genuine and forged have been performed using WD-XRF and cross-sectional analysis by SEM-EDX. The study conclusively shows that forged coin was manufactured by plating silver over baser metal alloy of copper and lead that caused segregation and brittleness owing to their reduced solid solubility. Silver was alloyed with a small percentage of copper or sometimes with copper and lead in original coins leading to age-hardening embrittlement in the ternary silver-copper-lead system on cooling. The presence of zinc and tin in some analyzed coins indicate copper was added as an alloy. All the coins were gold amalgamated with the help of mercury on either surface observed through WD-XRF. The silver/copper ratio indicates more than one mint. Preferential mineralization of more chemically active phase occurred as isolated patina shows the presence of oxides of lead, copper, silver, magnesium, and silica through XRD analysis.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 November 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, Volume 434〈/p〉 〈p〉Author(s): 〈/p〉

Description: 〈p〉Publication date: 1 January 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, Volume 438〈/p〉 〈p〉Author(s): Y.Z. Jia, W. Liu, B. Xu, S.L. Qu, T.W. Morgan〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The surface nano structures on W surface exposed to low-energy D plasma was studied by transmission electron microscopy. It was found that the surface nano structures on W surface induced by D plasma were mainly due to two reasons. First, the subsurface nano-sized bubbles will induce nano scale blistering of the surface, resulting in surface nano morphology. The nano scale blistering behaviour is most obvious on [1 1 1] surface at low temperature (500 K). Secondly, during the plasma exposure, oxide layer on W surface will be sputtered by low energy D particles, and the sputtering can also induce nano structures on some surfaces. At low temperature (500 K), the surface nano structures were formed due to the nano scale blistering behaviour and the sputtering of surface oxide layer. At high temperature (1000 K), the surface nano structures were mainly caused by the sputtering of surface oxide layer.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: Available online 30 October 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms〈/p〉 〈p〉Author(s): Wanwisa Sudprasert, Ridthee Meesat, Harry J. Whitlow, Henry Udeogu, Armin B. De Vera, Naresh Deoli〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉 〈p〉Mercury amalgams are still widely used in dentistry in many countries. There is considerable concern about uptake of Hg in both the patient and environment. It is an interesting question if the pathway is by Hg diffusion through the tissue of the tooth or dissolution in saliva or direct evaporation through inhaled air into the lung. Our previous study Meesat et al. (2017) of a high-Cu amalgam showed no evidence of diffusion through the enamel. However, a compositional change was observed on the biting surface of the amalgam which is indicative of tribochemical changes.〈/p〉 〈p〉To investigate the above observation in more detail, 17 adult teeth with amalgam fillings were obtained as operation-waste from dental clinics. The samples were embedded and sliced into 1 mm sections in the coronal plane of the tooth using a low/speed diamond saw with water-based cooling. Elemental maps from teeth treated with dental amalgam were measured using micro-PIXE.〈/p〉 〈p〉In common with our previous study Meesat et al. (2017), sharp interfaces between the enamel and amalgam were observed with no strong evidence for Hg diffusion in the enamel. Little evidence exists consistent with the presence of tribochemical alteration by mastication. However, Zn was observed to be localized at different sites in the amalgam/enamel interface.〈/p〉 〈/div〉 〈/div〉

Description: 〈p〉Publication date: Available online 10 December 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms〈/p〉 〈p〉Author(s): Harry J. Whitlow, Patrick Jeanneret, Edouard Guibert, Liping Wang, Mathijs Van Der Meer〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Time-of-flight-energy elastic recoil detection analysis (ToF-E ERDA) is a uniquely powerful thin-film analytical technique because it can be used to measure simultaneously the depth distributions of all elements in a thin-film sample. The basic design of the time detectors which are generally based on the electron mirror has not changed significantly over 25 years or so. A classic electron optical study has been made to elucidate the factors that limit the time resolution of electron mirror time pick off detectors and how they are interrelated. Degradation of the time resolution is mainly associated with the electron divergence from an ideal straight trajectory and variations in the propagation of electromagnetic pulses over the anode surface. A set of equations that can be used to optimise time detector design are presented along with a new configuration that has an expected time resolution of 40 ps fwhm and overcomes most of the drawbacks of the conventional configuration.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 February 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, Volume 440〈/p〉 〈p〉Author(s): Ruibin Li, Chaohui He, Wei Chen, Junlin Li, Chenhui Wang, Guizhen Wang, Chao Qi, Shanchao Yang, Xiaoming Jin, Yan Liu, Xiaoyan Bai〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Latch up (LU), an inherent destructive phenomenon owning to P-N-P-N structure in bulk Complementary Metal-Oxide -Silicon (CMOS) circuits, is highly sensitive to pulsed irradiation. A criterion for LU is concluded, and the impact of total ionizing dose (TID) on LU criterion is discussed. In the progress of accumulating TID, generated oxide trapped charges and interface states enhance surface recombination in the base of the parasitic bipolar junction transistor (PBJT), leading to increase of the base recombination current; and the trapped charges in the shallow trench isolation (STI) can also increase leakage current. In spite of hindering effect of the base recombination in PBJTs to LU, the STI leakage current plays a dominant role to gain sensitivity of LU. Experimental results confirm the fact that TID can lower the dose rate threshold for LU. For instance, the threshold in the device with doses 150 krad(Si) is nearly 50% lower than that in the pristine device. Simulations in SPICE and Sentaurus are conducted, and the results agree with that of experiments.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: Available online 7 December 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms〈/p〉 〈p〉Author(s): S.M. Tunhuma, M. Diale, J.M. Nel, M.J. Madito, T.T. Hlatshwayo, F.D. Auret〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉We have used confocal Raman spectroscopy, atomic force microscopy (AFM), Binary collision approximations and Deep level transient spectroscopy (DLTS) to study the defects introduced in n-type 4〈em〉H-〈/em〉SiC by 167 MeV Xe〈sup〉26+〈/sup〉 ions (swift heavy ions (SHIs)). Moderately doped epitaxial layers were irradiated with SHIs to a fluence of 5 × 10〈sup〉11〈/sup〉 cm〈sup〉−2〈/sup〉 at room temperature. Raman spectroscopy was used to investigate the effects of irradiation on the crystal structure. Raman intensity reduced after irradiation but the overall bond structure was conserved. Cluster spectra from confocal Raman spectroscopy showed a damage impact that was consistent with SRIM simulations. AFM showed that the incident radiation resulted in elongated protrusions. The virgin samples contained the E〈sub〉0.09〈/sub〉, E〈sub〉0.12〈/sub〉, E〈sub〉0.15〈/sub〉 and E〈sub〉0.65〈/sub〉 as the only electrically active defects. After irradiation the E〈sub〉0.40〈/sub〉 and E〈sub〉0.71〈/sub〉 defects were introduced.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 February 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, Volume 440〈/p〉 〈p〉Author(s): R.D. Perez, G.E. Falchini, F. Cometto Vincente, L. Soares, M.E. Poletti, H.J. Sánchez〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉 〈p〉Conventional x-ray fluorescence analysis (XRF) is a powerful instrumental technique for elemental quantification of samples with a wide range of matrices coming from industry, medicine, biology, environmental and archaeometry. The scattering of the x-ray tube excitation beam from the matrix is mainly responsible of the strong background in XRF spectra which restricts the detection limit (DL) to a few ppm (w/w). One possible strategy to reduce the DL is the monochromatization of the excitation beam with a crystal monochromator. In this case, the optimization of the system components is strongly required to obtain the highest excitation count rate over the sample, since it is considerable reduced by the short energy band pass of the monochromator.〈/p〉 〈p〉In the present work an optical device composed by a Si(100) crystal monochromator and two parallel plates beam guides (PPBG) was characterized and including in a conventional XRF spectrometer to improve the DLs. The PPBGs are composed by several thin glass plate reflectors placed together and separated by spacers. Inside the gap, x-rays are transmitted by total reflection contributing to the photon flux at the output of the optical device. The first PPBG reduces the divergence of the beam striking the crystal, and the second one collects the monochromatic beam that emerges from the crystal. In this way, the design of the optical device is quite compact keeping a high photon flux at the output thanks to the wide acceptance solid angle of the PPBGs. The new XRF spectrometer was applied to the analysis of biological tissues. The first results obtained in this field are shown in the present work where the performance of the spectrometer can be evaluated.〈/p〉 〈/div〉 〈/div〉

Description: 〈p〉Publication date: Available online 4 December 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms〈/p〉 〈p〉Author(s): M.M. Saifulin, J.H. O'Connell, A. Janse van Vuuren, V.A. Skuratov, N.S. Kirilkin, M.V. Zdorovets〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Bulk yttrium-iron garnet (YIG) single crystals have been irradiated with swift Kr and Xe ions having energies from 0.4 to 22.8 MeV/u and electronic stopping powers from 8.9 to 28.9 keV/nm near the irradiated surface. Transmission electron microscopy (TEM) has been used for direct observation of non-overlapping amorphous latent tracks in the near surface region of the irradiated bulk YIG crystals. The amorphous track radii observed in this work have been compared with previously reported data from direct and indirect measurements. It was found that the thickness of the sample subjected to swift heavy ion irradiation does not significantly affect the resulting amorphous track size observed by TEM in YIG. The results also support previously observed consistency between direct TEM and indirect Rutherford backscattering in channelling mode (RBS/C) and Mossbauer spectroscopy (MS) methods for amorphous track evaluation in YIG when electronic stopping power is greater than ∼13 keV/nm, which is sufficient to create cylindrical amorphous tracks by high velocity ions (〈em〉E〈/em〉 〉 10 MeV/u). Indirect methods provide underestimated values compared to TEM when the electronic stopping power is below ∼13 keV/nm, for which discrete amorphous tracks are supposed to be formed by high velocity ions.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 February 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, Volume 440〈/p〉 〈p〉Author(s): Christian Bäumer, Claus Maximilian Bäcker, Marcel Gerhardt, Erik Grusell, Benjamin Koska, Kevin Kröninger, Christian Nitsch, Hannah Rullkötter, Hilda Milani Siregar, Beate Timmermann, Nico Verbeek, Jörg Wulff, Azad Yazgan〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉 〈p〉This experimental study aims to measure nuclear cross sections from 〈sup〉nat〈/sup〉C and 〈sup〉27〈/sup〉Al which serve as reference targets regarding radioactivation in proton therapy. Graphite and aluminum foils were activated in broad, quasi-monochromatic proton fields generated with the pencil-beam scanning technique. The 〈em〉γ〈/em〉-emissions were analyzed subsequently in a nearby 〈em〉γ〈/em〉-ray spectrometry facility designed for low-level radioactivity measurements. The number of incident protons was measured with a Faraday Cup. A detailed evaluation of the uncertainties was performed.〈/p〉 〈p〉The cross section for the 〈sup〉nat〈/sup〉C(p,x)〈sup〉11〈/sup〉C reaction at 100 MeV is (70.2 ± 1.6 (sys.) ± 0.2 (stat.)) mb. The production cross sections from 〈sup〉27〈/sup〉Al at 100 MeV are (19.9 ± 0.4 ± 0.3) mb for 〈sup〉22〈/sup〉Na and (〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si35.gif" overflow="scroll"〉〈mrow〉〈mn〉11.5〈/mn〉〈mo〉±〈/mo〉〈mn〉0.3〈/mn〉〈/mrow〉〈/math〉〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si36.gif" overflow="scroll"〉〈mrow〉〈mo〉±〈/mo〉〈mn〉0.1〈/mn〉〈/mrow〉〈/math〉) mb for 〈sup〉24〈/sup〉Na. The systematic uncertainties contribute 2.0%–2.4% of the quoted uncertainties (〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si26.gif" overflow="scroll"〉〈mrow〉〈mi〉k〈/mi〉〈mo〉=〈/mo〉〈mn〉1〈/mn〉〈/mrow〉〈/math〉) of cross sections. Concluding, radioactivation cross sections were measured with proton fields in a clinically commissioned environment. The measured activation cross sections from aluminum used for monitoring of the proton fluence agree with the averaged values compiled in nuclear reaction data bases. For proton-induced radioactivation from carbon the chemical purity of the target strongly affects the experimental results. The cross section for the production of 〈sup〉11〈/sup〉C derived from a measurement with a high-purity graphite target is in line with the largest cross section obtained in prior studies.〈/p〉 〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 January 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, Volume 439〈/p〉 〈p〉Author(s): Toru Moriya, Mirei Takeyama, Hirohisa Sakurai, Toyoharu Umebayashi, Teiko Toyoguchi, Tadashi Shiraishi, Hiroko Miyahara, Motonari Ohyama, Kohei Nozawa, Satoshi Ito, Shigeru Itoh, Masashi Hirota, Fuyuki Tokanai〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉An accelerator mass spectrometry (AMS) system and an automated graphitization line were installed at Yamagata University (YU) in 2009. Approximately 2000 samples are measured per year using the YU-AMS system. The long-term stability of the system was assessed by measuring the standard sample IAEA-C7 graphitized by the automated graphitization line. In March 2014, a second automated graphitization line and an additional ion source for the YU-AMS system were installed to meet the requirement of 〈sup〉14〈/sup〉C measurement for pharmacological and medical applications. A phosphoric acid treatment system was also developed for the radiocarbon dating of calcium carbonate (CaCO〈sub〉3〈/sub〉) in shell and coral samples. Performance tests on the new YU-AMS system were carried out by measuring the C-series standard samples (C1-C9) and oxalic acid II (HOxII) obtained from IAEA and NIST, respectively. The results of the 〈sup〉14〈/sup〉C concentration pMC are in good agreement with the consensus values. Performance tests for medical applications were also carried out by measuring the 〈sup〉14〈/sup〉C concentration of 〈sup〉14〈/sup〉C-glucose in human plasma.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 February 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, Volume 440〈/p〉 〈p〉Author(s): R.A. Rymzhanov, S.A. Gorbunov, N. Medvedev, A.E. Volkov〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉A swift heavy ion leaves a damaged trail (SHI track) while penetrating through a solid. The radius of the track depends on the ion energy loss and velocity, and thereby on its penetration depth. Applying developed Monte Carlo code TREKIS and molecular dynamics approach we describe the damage distribution along the trajectory of an SHI (Xe and U) in olivine. This enables us to obtain the dependencies of the track radius and structure on the ion energy and its energy losses, as well as to identify the track formation thresholds in forsterite (Mg〈sub〉2〈/sub〉SiO〈sub〉4〈/sub〉) for fast and slow ions. It is found that the position of the maximal damage produced by an ion in a solid does not coincide with the Bragg peak of its electronic stopping. Loop-like dependence of the track radius on the electronic energy loss is identified.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 January 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, Volume 438〈/p〉 〈p〉Author(s): P. Marshall, A. Bayliss, S. Farid, C. Tyers, C. Bronk Ramsey, G. Cook, T. Doğan, S.P.H.T. Freeman, E. İlkmen, T. Knowles〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉This study tests whether accurate dating by AMS radiocarbon wiggle-matching short tree-ring series (c. 30 annual rings) in the period after AD 1510 can be achieved routinely. Such an approach has proved problematic for some intervals in the period AD 1160–1541 (Bayliss et al., 2017), which are before single-year calibration data are available (Stuiver, 1993). We suggest that such calibration data are essential if this approach is to be employed for the informed conservation of standing buildings.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 January 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, Volume 438〈/p〉 〈p〉Author(s): Carlos Vivo-Vilches, José María López-Gutiérrez, Manuel García-León, Christof Vockenhuber〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉 〈p〉Dealing with the 〈sup〉41〈/sup〉K interference during 〈sup〉41〈/sup〉Ca measurement with low energy AMS systems is challenging. The detection of 〈sup〉39〈/sup〉K to correct the measured 〈sup〉41〈/sup〉Ca/〈sup〉40〈/sup〉Ca ratios is a powerful tool that improves precision and accuracy. However, the study of the sources of this interference can help to reduce it to its minimum.〈/p〉 〈p〉In this work, it is shown that iron is a factor enhancing the production of the 〈sup〉41〈/sup〉K interference, since the (〈sup〉41〈/sup〉K〈sup〉57〈/sup〉Fe)〈sup〉−〈/sup〉 ion has the same mass as (〈sup〉41〈/sup〉K〈sup〉19〈/sup〉F〈sub〉3〈/sub〉)〈sup〉−〈/sup〉. To validate this observation, we measured 〈sup〉57〈/sup〉Fe〈sup〉2+〈/sup〉 together with 〈sup〉41〈/sup〉M〈sup〉2+〈/sup〉 (all ions with mass 41) and 〈sup〉39〈/sup〉K〈sup〉2+〈/sup〉 in a blank sample and an aluminum target at the 600 kV AMS system at ETH Zurich.〈/p〉 〈p〉We also show the temporal evolution of 〈sup〉41〈/sup〉M/〈sup〉40〈/sup〉Ca and 〈sup〉39〈/sup〉K/〈sup〉40〈/sup〉Ca ratios in two blank samples during a measurement on the 1 MV AMS system at CNA Seville. Even when unstable behavior for these ratios is observed for one of the blanks, the relationship between both, 〈sup〉41〈/sup〉M/〈sup〉39〈/sup〉K, is relatively stable over time. This supports the accuracy of the K–correction method, providing that it is applied sequence by sequence.〈/p〉 〈p〉Two programs, one for each of these compact AMS systems, were written in FORTRAN code to deal with the complexity of the data analysis due to the K-correction.〈/p〉 〈/div〉 〈/div〉

Description: 〈p〉Publication date: Available online 11 May 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms〈/p〉 〈p〉Author(s): Jing Wang, Qiang Qi, Maoqiao Xiang, Shouxi Gu, Yingchun Zhang, Guang-nan Luo〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉In fusion reactors, Li〈sub〉2〈/sub〉TiO〈sub〉3〈/sub〉 is one of the most promising candidates among solid breeder materials. However, Li〈sub〉2〈/sub〉TiO〈sub〉3〈/sub〉 will be reduced after heating under a reducing atmosphere resulting in a deficiency of oxygen. In the present study, the O-related defects introduced by reduction and their effect on the release behavior of hydrogen isotopes in Li〈sub〉2〈/sub〉TiO〈sub〉3〈/sub〉 were investigated by means of Raman spectroscopy, electron spin resonance and thermal desorption spectroscopy. O-related defects were confirmed as E-centers by electron spin resonance. The concentration of defects increased as the exposing temperature increased and then decreased when the temperature increased higher above 750 °C. The color of Li〈sub〉2〈/sub〉TiO〈sub〉3〈/sub〉 samples changed from white to dark blue after heating under deuterium and recovered to white again after annealing in air. This color change suggested a change from Ti〈sup〉4+〈/sup〉 to Ti〈sup〉3+〈/sup〉 due to a decrease in the oxygen content. Raman spectroscopy results indicated that there are no modifications in Li〈sub〉2〈/sub〉TiO〈sub〉3〈/sub〉 crystal structure, but on crystallinity. Thermal desorption spectroscopy showed the release behavior of deuterium has been affected considerably by O-related defects.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: Available online 3 May 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms〈/p〉 〈p〉Author(s): M. Saito, K. Holm, F.L. Bregolin, H. Hofsäss〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Herein, we describe new developments in the external coincidence elastic recoil detection analysis (coincidence ERDA) setup at the University of Göttingen. Our work aims to realize the quantitative evaluation of hydrogen in atmospheric pressure. The details of the developed device for the external coincidence ERDA, as well as the first spectra of the self-standing polymer foils are presented. We additionally prepared “wet” PVA foils with different water contents, and performed an external coincidence ERDA analysis. Using this setup, the increase in clear hydrogen and oxygen was observed as the foil contains more water. Since the external coincidence ERDA setup can offer greater flexibility for a variety of environments and the sample itself, this technique leads to a new method of moist sample characterization, and has potential for use in various 〈em〉in-situ〈/em〉/〈em〉operand〈/em〉 analyses.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 February 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, Volume 440〈/p〉 〈p〉Author(s): Brahim Touchrift, Houria Salah, Nadjia Benouali, Abdehamid Ziane〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉In this contribution, the presence of vicinage effects is demonstrated for H〈sub〉2〈/sub〉〈sup〉+〈/sup〉 ions slowing down in 20 nm thick aluminium target, using the 1.735 MeV resonance of 〈sup〉12〈/sup〉C(p, p)〈sup〉12〈/sup〉C elastic scattering. The stopping power ratio is deduced from the measured Elastic Backscattering Spectrometry (EBS) energy spectra of H〈sup〉+〈/sup〉 and H〈sub〉2〈/sub〉〈sup〉+〈/sup〉 ions using the simulation code IBA DataFurnace. An enhancement of 30% is found in the energy loss of the H〈sub〉2〈/sub〉〈sup〉+〈/sup〉 ions as compared to the atomic ones. The influence of the Coulomb explosion on the energy loss straggling was also examined. This is evaluated for 100 nm thick target by adjusting the energy loss and the straggling parameters while processing the experimental data. A theoretical treatment, based on the Lindhard dielectric formalism generalized by N.R. Arista to molecular ions, was used to calculate the stopping power ratio for aluminium for comparison.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 February 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, Volume 440〈/p〉 〈p〉Author(s): Hongyang Cui, Rong Wang, Deqiang Wei, Jiayue Huang, Jinyan Guo, Xinkai Li〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The mechanical properties of materials surface are always the key elements to evaluate the performance of materials, which means the surface performance of materials plays a key role especially in some occasion. In this study, the performance of T8, T10 and T12 steel were evaluated by using continuous scanning electron beam process (CSEBP) method for surface modification. The microstructure and properties of the modified layer were studied, and the influence of the electron beam process parameters on the modified layer was discussed. Surface modification of the materials was carried out by varying the beam current of the continuous electron-beam irradiation procedure. Comparing with the initial surface roughness of materials, the ultimate surface roughness was reduced significantly, and which the optimal surface roughness appeared at the beam current of 6 mA. These were all because of the surface shallow melting (SSM). Microstructure, microhardness and wear resistance of materials surface and cross-section after treatment with different processing parameters are investigated by using scanning electron microscope, microhardness meter and universal wear tester. Finally, the influence law of electron beam processing parameters on the modification layer is summarized.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 February 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, Volume 440〈/p〉 〈p〉Author(s): V. Chudinov, I. Kondyurina, V. Terpugov, A. Kondyurin〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Modern polyurethane elastomers are suitable materials for human implants. However, the immune system of an organism recognizes the polyurethane as a foreign body. A medical polyureaurethane, based on polyether, 2,4-toluenediisocyanate and aromatic diamine was treated by 20 keV nitrogen ions. The polyureaurethane surface was subsequently investigated by atomic force microscopy, electron spin resonance spectroscopy, Fourier transform infrared attenuated total reflection spectroscopy, wettability and surface energy analysis to observe the surface structure transformations associated with the ion implantation. The protein covalent attachment on the modified surface was observed. Endothelial cell attachment and proliferation showed preferences of the modified surface. Polyureaurethane samples were implanted into rats for 5 months. Histology data showed that the immune reaction to the modified polyureaurethane was weaker and the capsule wall is thinner for the modified polyureaurethane, than for the untreated polyureaurethane.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 January 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, Volume 439〈/p〉 〈p〉Author(s): Feng Liu, Chonghong Zhang, Chunqing He, Hai-Shan Zhou, Fang Ding, Guang-Nan Luo〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Tungsten (W) foils were irradiated with 122 MeV 〈sup〉〈sub〉20〈/sub〉〈/sup〉Ne ions at the Heavy-ion Research Facility in Lanzhou, on which an energy degrader for tailoring the depth distribution of implanting ions was used. SRIM calculation showed that a quasi-homogeneous distribution of atomic displacement damage to 0.16 dpa within a depth of 50 μm was produced in W. The features of radiation damage were characterized with positron annihilation life spectroscopy (PALS) and transmission electron microscopy (TEM) techniques in this study. Results from PALS study indicated that large vacancy clusters characterized by a long positron lifetime component of ∼510 ps were formed in the irradiated W. These clusters may be the nano-voids (an average diameter of ∼1 nm) exhibited in TEM imaging. Radiation-induced dislocation loops were also observed. Both perfect and Frank loops were manifested under the high resolution TEM observation. The experimental observation of a/2〈1 1 0〉 faulted loops in irradiated W was somewhat surprising and it may shed light on the origin of dislocation formation and their evolution in irradiated bcc metals.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 January 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, Volume 439〈/p〉 〈p〉Author(s): G. Laricchiuta, W. Vandervorst, J. Meersschaut〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Rutherford backscattering spectrometry (RBS) is an analysis method to quantify reference free the atomic areal density of a thin film, in particular sensitive to those cases where the elements of the film are heavier than the substrate. The ultimate sensitivity is determined by the ratio between the signal intensity from the thin film and the background signal originating from e.g. pulse pile-up events related to the scattering from the substrate atoms or dark noise intrinsic to the detector. We demonstrate that the sensitivity of RBS can be improved by reducing the pulse pile-up and dark noise background through the implementation of a magnet sector and a silicon strip detector as combined double energy dispersive analyzer. A limit-of-detection of 3∙10〈sup〉11〈/sup〉 Ru/cm〈sup〉2〈/sup〉 on Si is achieved.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 January 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, Volume 439〈/p〉 〈p〉Author(s): A. Hosseini, M.N. Nasrabadi, A. Esfandiarpour〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉In this research, in order to investigate primary radiation damage in iron nanofoam, simulation of displacement cascade near cylindrical nanovoids is performed using molecular dynamics. A primary knocked-on atom with 3, 6 and 9 keV energies and velocity parallel to the cylinder axis at 300 K is considered. 1–4 nanovoids are used as the model structure for free surfaces. It is identified that interaction between the displacement cascades and free surfaces is very sensitive to PKA energy and the distance of free surfaces. Near-surface cascade mechanism is observed when the displacement cascade interacts with a single cylindrical free surface, where clusters of bulk vacancies and a rim of adatoms are formed. In this case, based on the location of these defects rather free surface, two sub-mechanisms are identified. It is recognized that the degree of the penetration of the cascade into the cylindrical surfaces, plays an important role in forming vacancies and vacancy clusters in the ligament after the cooling of the cascade. Results show that when the PKA energy is 9 keV, enhancement of number of nanovoids increases the number of vacancies in the bulk. In this case, formation of vacancy planes is observed between the cylindrical nanovoids. The absorption of bulk vacancy clusters by the free surfaces is observed when displacement cascade is generated by a 6 keV PKA in close vicinity of four cylindrical surfaces.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 February 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, Volume 440〈/p〉 〈p〉Author(s): Y. Sasajima, N. Ajima, R. Kaminaga, N. Ishikawa, A. Iwase〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉In the present paper, we have extensively analyzed the atomic structures generated by supplying a thermal spike to the single crystal CeO〈sub〉2〈/sub〉 that we previously analyzed for specimens by the molecular dynamics method [Y. Sasajima et al., Nucl. Instr. Meth. B 314 (2013) 202]. Our analysis results were compared with the atomic structures obtained by the actual experiments using HAADF-STEM and ABF-STEM [S. Takaki et al., Nucl. Instr. Meth. B 326 (2014) 140]. Our simulation results and the experimental observations agreed well on the following point that the lattice of cerium is maintained while oxygen atoms migrate from their equilibrium cites. In particular, our simulation reproduced the distribution of the numbers of oxygen atoms obtained from the analysis of TEM images. The detailed process of generation and elimination of vacancies has also been analyzed as a function of time. We found that the number of vacancies was increased abruptly immediately after the thermal spike, and the number subsequently dropped through a relaxation process within 3 ps.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 February 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, Volume 440〈/p〉 〈p〉Author(s): Indudhar Panduranga Vali, Pramoda Kumara Shetty, M.G. Mahesha, V.G. Sathe, D.M. Phase, R.J. Choudhary〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉In this paper, the gamma irradiation effects on the structural and optical properties of N-doped 4H-SiC (n-4H-SiC) is presented up to a cumulative gamma radiation dose of 1500 kGy. The studies showed marginal and inconsistent variation in the 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si5.gif" overflow="scroll"〉〈mi〉c〈/mi〉〈/math〉- and 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si6.gif" overflow="scroll"〉〈mi〉a〈/mi〉〈/math〉-axis lattice constants of 4H-SiC due to the accumulation of gamma-induced defect states. The modifications in the longitudinal optical plasmon-phonon coupled (LOPC) modes, Biedermann absorption bands, Urbach energy (〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si7.gif" overflow="scroll"〉〈msub〉〈mi〉E〈/mi〉〈mi〉U〈/mi〉〈/msub〉〈/math〉) and defect related photoluminescence (DPL) bands are discussed at different (500, 1000 and 1500 kGy) irradiation doses. Despite these effects, the overall gamma-induced disorder (〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si3.gif" overflow="scroll"〉〈msub〉〈mrow〉〈mn〉1〈/mn〉〈mo〉-〈/mo〉〈mi mathvariant="normal"〉A〈/mi〉〈/mrow〉〈mrow〉〈mi mathvariant="normal"〉n〈/mi〉〈mi mathvariant="normal"〉o〈/mi〉〈mi mathvariant="normal"〉r〈/mi〉〈mi mathvariant="normal"〉m〈/mi〉〈/mrow〉〈/msub〉〈/math〉) and variation in the free carrier concentrations (〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si4.gif" overflow="scroll"〉〈mi〉n〈/mi〉〈/math〉) are found to be negligible and demonstrating the radiation resistant property of n-4H-SiC under gamma radiation environment.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 January 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, Volume 439〈/p〉 〈p〉Author(s): Tetsuya Matsunaka, Kimikazu Sasa, Tsutomu Takahashi, Seiji Hosoya, Masumi Matsumura, Yukihiko Satou, Shen Hongtao, Keisuke Sueki〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉To evaluate the environmental impact of 〈sup〉14〈/sup〉C discharged to the atmosphere from the Tokai nuclear facility during normal operational periods, cores were extracted from an 80-yr-old pine tree that grew close to the Tokai Nuclear Power Plants (Tokai NPP and Tokai-2 NPP) and the Tokai Reprocessing Plant (Tokai RP), and the 〈sup〉14〈/sup〉C levels in the annual rings were measured using accelerator mass spectrometry (AMS). The 〈sup〉14〈/sup〉C activity ranged from 232 to 403 Bq kg〈sup〉−1〈/sup〉 C in the tree rings formed during the period 1959–2013. The activities in the periods 1959–1965 and 2011–2013 represent the background levels, and the activities recorded between 1966 and 2010 are significantly elevated compared with these background levels, indicating uptake by the tree of 〈sup〉14〈/sup〉C discharged from the Tokai nuclear facility. The excess 〈sup〉14〈/sup〉C activity values of 1.1–70 Bq kg〈sup〉−1〈/sup〉 C for the period 1966–2010 are positively correlated with the estimated total annual 〈sup〉14〈/sup〉C discharges of 0.019–2.0 TBq from the Tokai NPP, Tokai-2 NPP, and Tokai RP (R〈sup〉2〈/sup〉 = 0.72; n = 40). This activity of 〈70 Bq kg〈sup〉−1〈/sup〉 C corresponds to an additional annual effective dose to the local population, via the food ingestion pathway, of less than 3.9 µSv yr〈sup〉−1〈/sup〉. These values are negligible compared with the average natural background radioactive dose in the world.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 February 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, Volume 440〈/p〉 〈p〉Author(s): L. Campajola, S. Braccini, P. Casolaro, D. de Luca, A. Ereditato, P.D. Häffner, P. Scampoli〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉For the first time the Rutherford Back-Scattering Spectroscopy (RBS) technique has been successfully exploited for the measurement of the energy of a proton beam accelerated by the IBA Cyclone 18/18 medical cyclotron in operation at the Bern University Hospital. This accelerator, routinely used for radioisotope production for Positron Emission Tomography (PET) imaging is equipped with an external beam line devoted to research activities in several fields such as detector physics, medical applications of particle physics, accelerator physics. Recently a widespread request has raised for the availability of well characterized proton and neutron beams, particularly for radiation hardness studies and the development of new neutron detectors. A feasibility study for a future upgrade of the Bern cyclotron towards a neutron facility was started, which requires a complete and precise characterization of the proton beam. Along this line, the measurement of fundamental parameters of the primary proton beam, such as the maximum proton energy and its spread have been performed by means of the RBS technique with two different targets, namely gold and graphite foils.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 February 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, Volume 440〈/p〉 〈p〉Author(s): Shengli Chen, David Bernard〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The Displacement per Atom (DPA) is one of the most important factors that influence the mechanical behaviors of materials during and after irradiation. However, the relativistic effect is not accounted for in typical calculations of DPA cross sections and Primary Knock-on Atom (PKA) spectra. The present work shows the computation of relativistic recoil energy. For incident energy lower than 20 MeV, the relativistic corrections are within 1% for neutron scattering reactions of 〈sup〉56〈/sup〉Fe and nuclei with mass larger than 〈sup〉56〈/sup〉Fe. The corresponding corrections on damage energy (equivalent to DPA with standard DPA metrics) is smaller than 0.5%. However, the relativistic effect is of importance for high incident energies, such as 200 MeV. For example, the relativistic recoil energy of continuum inelastic scattering is 10% higher than the classical one for all nuclei. The consideration of relativistic effect increases the recoil energy for the elastic scattering. Both positive and negative relativistic corrections are possible for both discrete and the inelastic scatterings. A consequent result is the broadening of PKA spectra.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: Available online 14 December 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms〈/p〉 〈p〉Author(s): P. Sigmund, V. Kuzmin, A. Schinner〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Reciprocity denotes the (approximate) equality of the electronic stopping cross section of element A in element B with the one of element B in element A. Reciprocity is expected in the energy range below 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si7.gif" overflow="scroll"〉〈mrow〉〈mo〉∼〈/mo〉〈mn〉0.1〈/mn〉〈/mrow〉〈/math〉 MeV/u. For ions heavier than protons, most measurements are performed by the transmission technique. In order to minimize nuclear energy loss, only a narrow beam of penetrating ions is allowed to enter the detector. This implies that also the electronic energy loss is underestimated. We have estimated the magnitude of the necessary correction on the basis of the PASS code and its influence on the expected reciprocity and find that reciprocity is not necessarily violated, even if the reported cross sections differ significantly. However, we also find differences between reported stopping cross sections and computed reduced stopping cross sections that we cannot reconcile on the basis of the PASS code. These differences are found to reflect the well-known 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si4.gif" overflow="scroll"〉〈mrow〉〈msub〉〈mrow〉〈mi〉Z〈/mi〉〈/mrow〉〈mrow〉〈mn〉1〈/mn〉〈/mrow〉〈/msub〉〈/mrow〉〈/math〉 structure, which is not inherent in the present version of PASS.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: Available online 14 December 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms〈/p〉 〈p〉Author(s): A.I. Titov, P.A. Karaseov, K.V. Karabeshkin, G.M Ermolaeva, V.B. Shilov〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Optical effects induced in silicon-doped wurtzite (0001) GaN epilayers by keV monatomic and molecular ion irradiation were experimentally investigated. Results were analyzed together with data on structure defect formation. In all the cases under consideration, an increase in the collision cascade density (the cases of molecular and heavy atomic ion bombardment) enhances the stable damage accumulation rate and, accordingly, intensifies quenching of luminescence. The processes of PL suppression were theoretically considered as an increase of surface recombination rate of nonequilibrium photo-excited charge carriers due to production of stable damage at the irradiated subsurface layer. It is shown that carrier diffusion determines PL decay time shortening in the shallow implantation cases studied.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 January 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, Volume 439〈/p〉 〈p〉Author(s): Ravi Bhushan, M.G. Yadava, Manan S. Shah, Harsh Raj〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉A 1 MV Accelerator Mass Spectrometer (AMS) has been installed at Physical Research Laboratory (PRL), Ahmedabad, India which is tuned for measurement of 〈sup〉14〈/sup〉C, 〈sup〉10〈/sup〉Be and 〈sup〉26〈/sup〉Al and is fully operational. The facility is acronymed as PRL-AURiS (PRL-Accelerator Unit for Radioisotope Studies). Measurements on various reference materials, have demonstrated its ability to achieve precision for 〈sup〉14〈/sup〉C, 〈sup〉10〈/sup〉Be and 〈sup〉26〈/sup〉Al to 2.2, 4.8 and 5.3‰ levels, with background values of 3.9 × 10〈sup〉−16〈/sup〉, 5.8 × 10〈sup〉−16〈/sup〉 and 1.6 × 10〈sup〉−14〈/sup〉 respectively.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 February 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, Volume 441〈/p〉 〈p〉Author(s): Slavica B. Maletic, Dragana D. Cerovic, Jablan R. Dojcilovic〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉In this study, we investigated a modification of the structure of polyethylene terephthalate (PET) membrane exposed to 100 keV N〈sup〉5+〈/sup〉 ions with fluences varying from 10〈sup〉14〈/sup〉 to 10〈sup〉16〈/sup〉 ions/cm〈sup〉2〈/sup〉. The changes in the properties of the ion-beam modified samples of PET membrane were analyzed by Fourier transform infrared (FTIR) spectroscopy, ultraviolet–visible (UV–Vis) and dielectric spectroscopies. FTIR spectra showed a change in the intensity of the typical bands after the irradiation of the polymers. The results of the optical measurements showed that the increase in the ion irradiation fluence induced a decrease in the transmittance of the PET membrane. The estimated value of the energy band gap decreased with the increase of the fluence. A significant decrease of the energy band gap was observed for the ion beam fluence of 10〈sup〉16〈/sup〉 ions/cm〈sup〉2〈/sup〉. The dielectric measurements performed in a wide frequency band in the range from 20 Hz to 10 MHz and temperature range from 120 K to 400 K revealed that ion beam treatment with a fluence of 10〈sup〉16〈/sup〉 ions/cm〈sup〉2〈/sup〉 changed the characteristic temperature dependence of the dielectric loss tan〈em〉δ〈/em〉 (T).〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: Available online 22 December 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms〈/p〉 〈p〉Author(s): Susanne Lindauer, Ronny Friedrich, Robin van Gyseghem, Bernd R. Schöne, Matthias Hinderer〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The Mini Carbon Dating System (MICADAS) represents a flexible AMS system for measuring radiocarbon samples either in the form of graphite or CO〈sub〉2〈/sub〉 gas. We used the possibility to attach a carbonate handling system (CHS) to the gas ion source (GIS) to measure smaller amounts of carbonates (〈500 µg) than is usually required for graphite samples (1 mg). We determined a blank correction for different sample sizes (F〈sup〉14〈/sup〉C ranging from ∼0.0045 to ∼0.017) from graphs. The use of OXA II as solid target and as gas fed through the GIS is presented. Cross-contamination is detected to be in the range of ∼6%, but depends on the sample size and 〈sup〉14〈/sup〉C content of the previous sample. Our system delivers reliable data for sample sizes down to 30 µg C when enough blanks (here 〉 3) are used to clean the system. We tested the CHS-GIS combination on heated and unheated archaeological shells of 〈em〉Anadara uropigimelana〈/em〉 from Kalba, Sharjah Emirate, United Arab Emirates (UAE). Even though the amount of carbon in the samples was small (4–22 µg C) the performance of the CO〈sub〉2〈/sub〉 dating system permits the comparison of trends in the 〈sup〉14〈/sup〉C data to stable isotope measurements (δ〈sup〉18〈/sup〉O and δ〈sup〉13〈/sup〉C). With 10–20 µg C, however, our sample sizes were too small, suffering from cross-contamination and elevated blanks, and our blank samples prior to the small samples were not enough. Hence, an interpretation in combination with the stable isotope data was not possible beyond comparison of trends.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 February 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, Volume 440〈/p〉 〈p〉Author(s): Shudi Zhang, Zhisen Liang, Wei Hang, Zhilin Yang, Bin Yu, Weibu Wang〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉 〈p〉Laser-induced tip-enhanced ablation appears to be a promising nanometer-scale sampling approach. Recently we have developed a Near-Field Ablation and Ionization Mass Spectrometer, which is capable of direct ablation and ionization of materials at a scale of tens of nanometers under both nanosecond and femtosecond pulsed lasers. In spite of its great potential as a nanometer-scale sampling source, its underlying mechanism remains to be further explored.〈/p〉 〈p〉To figure out the difference between nanosecond and femtosecond laser-induced tip-enhanced ablations, we developed a three-dimensional theoretical code to explain the ablation phenomena on a Ti-coating sample. With calculated time-evolving and space-distribution features of sample temperature, the simulation justified the time needed to reach electron-lattice thermal equilibrium to be within several picoseconds, and showed that nanosecond laser ablation features much greater thermal effect. We also calculated the theoretical ablated pit profiles and volume after one laser pulse under both lasers. They all fitted well with experimental results. Afterwards, we compared the experimental mass spectra of various salts in the nanosecond and femtosecond laser experiments and studied the roles of properties via chemometrics works. Result again revealed that thermal properties contributed relatively more in the nanosecond laser model. Ionization potential was equally important in both experiments, which met well with the intensity distribution observed in the mass spectra. Moreover, the influences of lattice energy, molar mass and fusion heat were also explained. All these results proved and supported each other, which verifies our study to be reasonable and helps us get a better understanding of this new technique.〈/p〉 〈/div〉 〈/div〉

Description: 〈p〉Publication date: Available online 23 December 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms〈/p〉 〈p〉Author(s): Yasunori Mahara, Tomoko Ohta〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉In 2001, a borehole was drilled to 400 m depth below the ground surface of a tableland in northern Japan, where horizontal porous sedimentary rock strata are deposited. Fresh drill-core and groundwater samples were collected from the borehole for estimating global fallout bomb pulses of 〈sup〉3〈/sup〉H, which becomes tritiogenic 〈sup〉3〈/sup〉He (tri〈sup〉3〈/sup〉He) through β-decay, and 〈sup〉36〈/sup〉Cl. In the northern hemisphere, the maximum fallout deposition of 〈sup〉36〈/sup〉Cl from nuclear testing was observed during 1954–1957, and that of 〈sup〉3〈/sup〉H in 1963. Most 〈sup〉3〈/sup〉H (half-life 12.3 y) in the rock porewater had decayed to tri〈sup〉3〈/sup〉He during the 38 years between 1963 and 2001. In the borehole, bomb pulses were observed in profiles of tri〈sup〉3〈/sup〉He and 〈sup〉36〈/sup〉Cl/Cl at 101 m and around 138 m depth below the ground surface, respectively. The downward groundwater velocity was estimated to be 2.9–3.1 m/y from the depth of the 〈sup〉36〈/sup〉Cl/Cl bomb pulse and 2.7 m/y from the depth of the tri〈sup〉3〈/sup〉He bomb pulse. Although the two velocity estimates differ by 10–15%, it is possible to model groundwater flow in the tableland as downward piston flow without diffusion.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: Available online 21 December 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms〈/p〉 〈p〉Author(s): E. Kaniukov, V. Bundyukova, D. Yakimchuk, A. Shumskaya, Yu. Bogatyrev, S. Lastovskii, S. Demyanov〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Structures containing a nickel precipitate in the pores of silicon oxide were obtained by ion-track technology. The SiO〈sub〉2〈/sub〉(Ni)/Si structures were exposed under irradiation with 〈sup〉60〈/sup〉Co gamma quanta with energy of 1.25 MeV at the dose up to 1.5 × 10〈sup〉5〈/sup〉 Gy. The electrophysical and galvanomagnetic characteristics of the SiO〈sub〉2〈/sub〉(Ni)/Si structures before and after irradiation were studied and the influence of ionizing radiation on their electrical resistivity and magnetoresistance was discussed. The use of SiO〈sub〉2〈/sub〉(Ni)/Si structures as a sensitive element of radiation-resistant magnetic field sensors was proposed.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 January 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, Volume 439〈/p〉 〈p〉Author(s): R. Rathika, M. Kovendhan, D. Paul Joseph, A. Sendil Kumar, K. Vijayarangamuthu, C. Venkateswaran, K. Asokan, S. Johnson Jeyakumar〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The physical properties of thin films can be modified by swift heavy ion (SHI) beam irradiation of the target material. Spray-deposited tungsten trioxide (WO〈sub〉3〈/sub〉) thin films of thickness 89 nm were irradiated with 200 MeV Ag〈sup〉15+〈/sup〉 ion beam at various fluences of 5 × 10〈sup〉11〈/sup〉, 1 × 10〈sup〉12〈/sup〉, 5 × 10〈sup〉12〈/sup〉〈sub〉,〈/sub〉 and 1 × 10〈sup〉13〈/sup〉 ions/cm〈sup〉2〈/sup〉. The X-ray diffraction pattern of the pristine film was orthorhombic, while the irradiated film became amorphous at different fluences except for 5 × 10〈sup〉12〈/sup〉 ions/cm〈sup〉2〈/sup〉; this may be due to the re-crystallization effect induced by irradiation. The observed Raman modes for the pristine film were in good agreement with those reported for the irradiated WO〈sub〉3〈/sub〉 films. The intensity of Raman peaks decreased upto 5 × 10〈sup〉12〈/sup〉 ions/cm〈sup〉2〈/sup〉 and vanished completely at further higher fluences. The optical transparency of the pristine film was much higher than that of irradiated ones. Both the direct and indirect band gaps showed a red shift. AFM data revealed significant surface modifications after irradiation. Transport properties were also studied for both the pristine and irradiated films by the Hall effect. A decrease in resistivity was observed with the increase in fluence. These results are discussed in this paper.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 January 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, Volume 439〈/p〉 〈p〉Author(s): Kazuki Oguni, Koji Sato, Yosuke Ishii, Yukari Ishikawa, Shinji Kawasaki, Andrii Vasin, Shunsuke Muto〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉We examined the evolution of electron-radiation-induced defects in a white-luminescent, carbonized, mesoporous silica nanocomposite using cathodoluminescence (CL) and electron energy-loss spectroscopy associated with scanning transmission electron microscopy, in order to elucidate the microscopic origins of light emissions in the visible spectral range. The effects of electron irradiation on CL were analyzed based on the differential equations for kinetics of irradiation defects. The nanometric honeycomb silica framework was found to play essentially no role in the electron-excited light emission processes, in contrast to the case for photon-excited processes. The broad and continuous visible emission band in CL consisted of several luminescence components, that have been assigned to optically active point defects such as oxygen-deficient centers, and surface nonbridging oxygen hole centers (NBOHCs) in silica glass.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 January 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, Volume 439〈/p〉 〈p〉Author(s): 〈/p〉

Description: 〈p〉Publication date: 15 January 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, Volume 439〈/p〉 〈p〉Author(s): Longyan Hou, Yiyong Wu, Jingdong Xiao, Bin Guo, Yingying Zong〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The optical properties and microstructure degradation of 4,4′-diaminodiphenylmethane (DDM)-cured epoxy after 170 keV vacuum electron irradiation were investigated in the paper. It was found that the colorless DDM-cured epoxy turned to be green after electron irradiation. Ultraviolet–Visible (UV–vis) spectra analysis showed that irradiation resulted in two absorption peaks appearing at wavelengths of 406 and 636 nm, respectively. The main absorption at the peak of 636 nm was attributed to n → π〈sup〉*〈/sup〉 transition and mainly responsible for the green color appearance. Distinguishable cyclohexadienyl-type radicals were detected using electron paramagnetic resonance spectra (EPR), wherein the central peak in the EPR spectrum was assigned to the green chromophore. It is an interesting result that the annealing kinetics of the radical and optical properties after irradiation with fluence of 5 × 10〈sup〉14〈/sup〉cm〈sup〉−1〈/sup〉 were coincidently found to follow a sum of an exponential and a linear mode with the storage time at room temperature and to have almost equal characteristic time constant. And after infrared spectroscopy analysis, the annealable green chromophore was proposed to be assigned to the quinone-type radical.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 January 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, Volume 439〈/p〉 〈p〉Author(s): J. Habainy, Y. Lee, K.B. Surreddi, A. Prosvetov, P. Simon, S. Iyengar, Y. Dai, M. Tomut〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The spallation material at ESS is pure tungsten, which is cooled by gaseous helium flow. To study the behaviour of tungsten under dynamic beam conditions at ESS, pure tungsten specimens have been irradiated at the M3-beamline of the UNILAC facility at GSI Helmholtz Centre for Heavy Ion Research. Tungsten specimens of two thicknesses, 26 μm and 3 mm, were exposed to pulsed uranium and gold ion beams for fluences up to 7.5 · 10〈sup〉13〈/sup〉 ions·cm〈sub〉−2〈/sub〉 at 4.8 MeV/nucleon. Nanoindentation tests were performed on the cross section of the irradiated 3 mm sample, and microhardness was measured on the top surface. The measured data are compared with the calculated damage values, and a correlation between the radiation induced damage and the observed mechanical property is presented. Thermal diffusivities of foil samples irradiated up to four different fluences were measured with a Laser Flash Apparatus (LFA). The observed changes in the mechanical and thermal properties of irradiated tungsten were used to estimate the changes of operational temperature and mechanical stresses in the ESS target material with the progress of radiation damage, using coupled thermal and mechanical simulations. From the pulsed beam induced dynamic oscillations of thin tungsten specimens, information on fatigue properties of tungsten under irradiation was drawn. In addition to pure tungsten, oxidised tungsten samples were irradiated. This is to investigate the stability of the adhesive oxide layer under pulsed beam conditions, which would be formed due to oxygen impurities in the helium cooling loop. The irradiated oxide scale was examined using Auger Electron Spectroscopy (AES) and Scanning Electron Microscopy (SEM).〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 January 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, Volume 439〈/p〉 〈p〉Author(s): Sascha Maxeiner, Hans-Arno Synal, Marcus Christl, Martin Suter, Arnold Müller, Christof Vockenhuber〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉A proof-of-principle experiment of a compact 300 kV multi-isotope AMS system is presented. An existing spectrometer (Tandy 500 kV AMS system) was combined with a novel 300 kV vacuum insulated tandem acceleration unit. Based on new models and simulation tools, the stripper geometry and acceleration was optimized for He stripping at low energies and was adapted to the spectrometer’s ion optics. AMS measurements of Be-10 and Al-26 were performed with the degrader foil method and a prototype passive absorber, respectively, while isobar correction methods were applied for Ca-41 measurements. Further tests were performed with I-129 and the actinides (uranium). The results are presented and show high efficiencies with overall transmissions of up to 50% and an improvement of abundance sensitivity of an order of magnitude for actinides. Based on the results a new compact (300 kV) multi-isotope AMS system has been designed which will require less than 25 m〈sup〉2〈/sup〉 of floor space.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 January 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, Volume 439〈/p〉 〈p〉Author(s): A. Stolz, A. Dewald, S. Heinze, R. Altenkirch, G. Hackenberg, S. Herb, C. Müller-Gatermann, M. Schiffer, G. Zitzer, A. Wotte, J. Rethemeyer, T. Dunai〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉 〈p〉Since 2015, the CologneAMS started operating a second SO-110 B ion source (Arnold et al., 2010; Klein and Mous, 2017) from High Voltage Engineering Europe (HVE) with a gas injection system (GIS) from Ionplus AG (Wacker et al., 2013) for the measurement of gaseous CO〈sub〉2〈/sub〉 samples. Significant effort was spent increasing the efficiency of 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si2.gif" overflow="scroll"〉〈mrow〉〈msup〉〈mrow〉〈mtext〉C〈/mtext〉〈/mrow〉〈mrow〉〈mo〉-〈/mo〉〈/mrow〉〈/msup〉〈/mrow〉〈/math〉 ion beam extraction as well as the operational reliability. Details are described in Stolz et al. (2017).〈/p〉 〈p〉Recent work was aimed at prolonging the cleaning intervals and allowing unattended routine 〈sup〉14〈/sup〉CO〈sub〉2〈/sub〉 measurements. Problems related to sparking inside the source chamber could be eliminated by electrically shielding the ceramic linear actuator that is used to move the target pieces into the source head. Furthermore, the Cs reservoir temperature was decreased from 135 °C to 120 °C. The negative ion formation efficiency has dropped only slightly to about 5% with the current settings. Additionally, the GIS sample magazine capacity was doubled to 16 ampules, which enables longer measurements without user interaction.〈/p〉 〈p〉A dedicated software (Gas Injection Control Software, GICS) was developed that controls GIS and AMS hardware for fully autonomous measurements, including the source and accelerator startup, sample cracking or combustion, sample mixing with the He carrier gas and the transfer to the source, as well as the subsequent data analysis. This tool also comprises error detection routines in order to minimize the risk of losing a sample due to hardware failures.〈/p〉 〈p〉The blank value was reduced from typically 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si3.gif" overflow="scroll"〉〈mrow〉〈mn〉7〈/mn〉〈mo〉·〈/mo〉〈msup〉〈mrow〉〈mn〉10〈/mn〉〈/mrow〉〈mrow〉〈mo〉-〈/mo〉〈mn〉15〈/mn〉〈/mrow〉〈/msup〉〈/mrow〉〈/math〉 to 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si4.gif" overflow="scroll"〉〈mrow〉〈mo〉∼〈/mo〉〈mn〉3〈/mn〉〈mo〉·〈/mo〉〈msup〉〈mrow〉〈mn〉10〈/mn〉〈/mrow〉〈mrow〉〈mo〉-〈/mo〉〈mn〉15〈/mn〉〈/mrow〉〈/msup〉〈/mrow〉〈/math〉. This was achieved by modifications in the cleaning and measurement procedures.〈/p〉 〈p〉Recently a EuroVector EA3000 elemental analyzer (EA) was coupled to the GIS and integrated into the GICS software. First EA test measurements with standards, blanks and tree rings were performed as well as first automated overnight measurements with ampules and EA samples.〈/p〉 〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 January 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, Volume 439〈/p〉 〈p〉Author(s): X.F. Ding, D.P. Fu, P. Gao, L.P. Zhou, K.X. Liu〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉A project of 〈sup〉14〈/sup〉C trace on deep water in South China Sea requires an accuracy of AMS radiocarbon measurement better than 2.5‰, which is higher than the accuracy for routine measurements of the NEC compact AMS system at Peking University. A series of modifications have enhanced the stability of the AMS system, minimizing fractionation effects and improving the accuracy and quality control of measurements. The ripple of terminal voltage has been reduced from 100 V to less than 50 V. The variation of beam currents from different samples is within 20% and a special tool is designed for proper installation of sample wheels. Measurements on standards and secondary samples demonstrate an improvement in accuracy to 〈2.5‰.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 January 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, Volume 439〈/p〉 〈p〉Author(s): Jing Hu, Yulei Fu, Dong Li, Yingmou Zhu, Ruixue Zhang, Wansheng Zhao〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The metal treatment by high energy electron beams is a complicated process consisting of multiple physical mechanisms, which is challenging for the accurate description and prediction of the electron beam treatment process by theoretical and simulation methods. In this work, a hybrid particle-thermodynamic model is developed to calculate the transient temperature distributions of the electron beam irradiated metal surface and thus to predict the surface topography and quality of the metal after irradiation treatment. Both the electron beam profile and its interaction with the solid material are calculated by a Monte-Carlo code as a Double-Gaussian heat source. The simulation results by the particle-thermodynamic model with accurate intensity distributions of the electrons as the input heat source are applied to determine the temperature field of the irradiated area and to predict the surface topography under a range of metal processing parameters. The optimal processing parameter range is also derived based on the model. The simulation results which are validated by the experimental results on 30CrMnSiA under given processing parameters show that the hybrid particle-thermodynamic model is capable of presenting the highly transient temperature distributions after the electron-material interactions and determining the optimal processing parameters for the metal treatment process.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 January 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, Volume 439〈/p〉 〈p〉Author(s): 〈/p〉

Description: 〈p〉Publication date: Available online 10 December 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms〈/p〉 〈p〉Author(s): A. Boulle, A. Chartier, J.-P. Crocombette, T. Jourdan, S. Pellegrino, A. Debelle〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Radiation damage in materials is a space and time multi-scale process, ranging from the atomic scale up to the macroscopic scale, and from the femtosecond up to several years. The prediction of the long term evolution of materials subjected to radiative environments (in the nuclear or in the space industry, as well as in the field of microelectronics) therefore requires the combination of several simulation and experimental techniques able to cover the different space and time scales involved. X-ray diffraction (XRD) is highly sensitive to atomic displacements while probing macroscopic volumes of material. In this respect it is perfectly suited for the study of radiation damage. In this work it is shown how XRD can be quantitatively and qualitatively used in combination with numerical simulations, like molecular dynamics and rate-equation cluster dynamics, to analyze damage build-up in irradiated SiC and ZrC single crystals. Particular emphasis is laid on the methodological aspects of XRD data treatment in order to extract parameters such as damage-induced strain and disorder.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 February 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, Volume 440〈/p〉 〈p〉Author(s): Weiyue Zhou, Kevin B. Woller, Guiqiu (Tony) Zheng, Peter W. Stahle, Michael P. Short〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Aside from the historical Molten Salt Reactor Experiment, a few in-reactor loops, and one electron irradiation/corrosion facility, dedicated facilities to test the combined effects of molten salt corrosion and irradiation on materials do not currently exist. A major gap therefore exists in rapid, reactor-relevant materials testing capabilities which, if remedied, would greatly hasten molten salt reactor development. We present a new accelerator-based facility for rapid, simultaneous testing of molten salt-facing materials utilizing a proton beam as the radiation source. Introducing proton irradiation to a molten salt corrosion system poses specific engineering concerns in sample and corrosion cell design, operational stability, integration with the accelerator beamline, and radiation safety. This paper describes how these requirements were fulfilled with confirmatory tests and results.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 February 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, Volume 440〈/p〉 〈p〉Author(s): S.J. Moloi, M. McPherson〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The annealing behaviour of irradiated silicon 〈em〉p〈/em〉-〈em〉i〈/em〉-〈em〉n〈/em〉 diodes has been investigated by use of 〈em〉I〈/em〉–〈em〉V〈/em〉 measurements. The radiation-induced damage is achieved by the use of 1 MeV neutrons. The results have been analysed and a striking feature is easily noticeable where defects that do not anneal out alter their activity and behave more as generation centres. This means that they are situated in the upper half of the band gap where they act to increase the carrier density and the measured current. The increase in current starts to occur at around 100 days and a change in trap activity at around 180 days after irradiation. The device behaviour, however, remains ohmic throughout indicating that a defect level that is responsible for relaxation behaviour is stable. This study would assist in demonstrating stability of silicon radiation detectors during their operational time.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 February 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, Volume 440〈/p〉 〈p〉Author(s): Hiroki Sakata, Yuichi Yamamoto, Koya Sato, Kaoru Nakajima, Kenji Kimura〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Composition depth profiles of soda-lime silicate glasses were measured using high-resolution Rutherford backscattering spectroscopy (HRBS) and high-resolution elastic recoil detection analysis (HERDA). Surface enrichment of modifier cations (Na〈sup〉+〈/sup〉 and Ca〈sup〉2+〈/sup〉) followed by a depletion in the deeper regions was observed using HRBS. The observed surface enrichment was attributed to the effect of radiation damage caused by the He〈sup〉+〈/sup〉 irradiation. It was shown that the precise depth profiling of glass surfaces can be performed using HRBS when the fluence is limited below 3 × 10〈sup〉14〈/sup〉 He ions cm〈sup〉−2〈/sup〉. HERDA measurements demonstrated that there is a substantial amount of hydrogen (7.3 ± 1.3 × 10〈sup〉21〈/sup〉 hydrogen cm〈sup〉−3〈/sup〉) in the subsurface region as well as on the surface (1.6 ± 0.2 × 10〈sup〉15〈/sup〉 hydrogen cm〈sup〉−2〈/sup〉), which is very different from the silica glass surface where no subsurface hydrogen was observed.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 February 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, Volume 440〈/p〉 〈p〉Author(s): Wataru Takeuchi〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The interatomic potentials between projectiles and target atoms have a strong influence on the rainbow angles corresponding to pronounced peaks in the angular distributions of scattered projectiles with slight angle, attributed to rainbow scattering (RS), under axial surface channeling conditions. Schüller and Winter (SW) (2009) have measured the dependence of rainbow angles on normal energies to the target surface of projectile energy in RS of reactive N atomic projectile under 〈1 0 0〉 axial channeling conditions at a Al(0 0 1) metal surface with projectile energies of 10–70 keV. The SW’s data were analyzed by computer simulations using the ACOCT code based on the binary collision approximation with interatomic pair potentials. The agreement between the ACOCT results using the ZBL pair potential with only a repulsive part and the experimental ones was found in RS for projectile energy of 70 keV. The experimental results included the dynamic effects indicating that rainbow angles increase with decreasing projectile energies at low normal energies were roughly reproduced by the ACOCT simulations for the HF-like pair potentials with an attractive part depending on projectile energies.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: Available online 3 December 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms〈/p〉 〈p〉Author(s): Yunqing Xiao, Yuanqing Shi, Pinyang Liu, Yachao Zhu, Lei Gao, Yanling Guo, Lin Chen, Ximeng Chen, Vladimir A. Esaulov〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Li〈sup〉+〈/sup〉 and Na〈sup〉+〈/sup〉 ions are scattered from Au(1 1 0) and Au(1 1 1) surfaces in the keV-energy range, respectively. The pronounced Li° and Na° fractions non-monotonically vary with incident energy and exit angle for high work function gold surfaces. In particular, the azimuthal angle dependence of Li° fraction has been observed at low incident energies for a grazing exit angle. The simple calculations are presented to compare with the experimental data. Our findings clearly indicate that both the perpendicular and parallel exit velocity affect the final neutral fraction.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: Available online 4 December 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms〈/p〉 〈p〉Author(s): R.A. Khmelnitski, V.V. Kononenko, J.H. O'Connell, V.A. Skuratov, G.F. Syrykh, A.A. Gippius, S.A. Gorbunov, A.E. Volkov〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉 〈p〉Diamond preliminary damaged with neutrons was irradiated with swift heavy ions (SHI, 1030 MeV 〈sup〉209〈/sup〉Bi) decelerated in the electronic stopping regime as well as with fs-laser pulses. The initial excess electronic energy densities appearing in the nanometric vicinity of the SHI trajectories and within the absorbing layers in laser spots were comparable (∼10〈sup〉24〈/sup〉 eV cm〈sup〉−3〈/sup〉).〈/p〉 〈p〉Graphitization of diamond in the central parts of the lased spots was observed above the threshold fluence of 15–30 J/cm〈sup〉−2〈/sup〉. It was also found that the lower threshold fluence is required for initiating graphitization as well as destruction of the pre-damaged crystal by laser pulses in comparison to that for undamaged diamond. This indicates a noticeable effect of an existing defect ensemble on the kinetics of diamond transformations in laser spots.〈/p〉 〈p〉However, X-ray diffraction, atomic-force microscopy, and electron microscopy detected no graphitic domains within the SHI-irradiated pre-damaged crystal.〈/p〉 〈p〉The research demonstrated that the density of the initial excess electronic energy cannot be treated as the sole parameter governing subsequent structure transformations in diamond. Large differences between the spatial as well as temporal scales finally results in different pathways of the relaxation kinetics of this excess energy in laser spots and SHI tracks in diamond.〈/p〉 〈/div〉 〈/div〉