ALBERT

Beschreibung: A smart monitoring system for superconducting cable test is proposed with an adaptive current control of a superconducting transformer secondary. The design, based on Fuzzy Gain Scheduling, allows the controller parameters to adapt continuously, and finely, to the working variations arising from transformer nonlinear dynamics. The control system is integrated in a fully digital control loop, with all the related benefits, i.e., high noise rejection, ease of implementation/modification, and so on. In particular, an accurate model of the system, controlled by a Fuzzy Gain Scheduler of the superconducting transformer, was achieved by an experimental campaign through the working domain at several current ramp rates. The model performance was characterized by simulation, under all the main operating conditions, in order to guide the controller design. Finally, the proposed monitoring system was experimentally validated at European Organization for Nuclear Research (CERN) in comparison to the state-of-the-art control system [P. Arpaia, L. Bottura, G. Montenero, and S. Le Naour, “Performance improvement of a measurement station for superconducting cable test,” Rev. Sci. Instrum.83, 095111 (2012)] of the Facility for the Research on Superconducting Cables, achieving a significant performance improvement: a reduction in the system overshoot by 50%, with a related attenuation of the corresponding dynamic residual error (both absolute and RMS) up to 52%.

Beschreibung: This paper presents a method which uses the characteristics of the etch pits induced in a polyallyl-diglycol-carbonate (PADC) detector of the CR-39/PM-355 type to estimate particle energy. This method is based on the data provided by a semiautomatic system that selects tracks according to two parameters, crater diameters, and mean gray level values. In this paper we used the results of the calibration measurements that were obtained in our laboratory in the period 2000–2014. Combining the information on the two parameters it is possible to determine unambiguously the incident projectile energy values. The paper presents the results of an attempt to estimate the energy resolution of the method when analyzing the tracks produced in the CR-39/PM-355 detector by energetic ions such as alpha particles, protons, and deuterons. We discuss the energy resolution of the measurement of light charged particle energy which is based on the parameters (crater diameter and mean gray level value) of tracks induced in solid state nuclear track detectors of the PADC type.

Beschreibung: In this work, an automated apparatus for driving single electrostatic probes and acquiring the plasma-related data has been designed and fabricated. The voltage range of the present system is ±110 V with an adjustable voltage step as low as 3 mV. Voltage and current measurements are carried out with high resolution and high accuracy circuits, both based on 16 bit analog-to-digital converters. The code embedded in a micro-controller, schedules the operation of the device and transfers the experimental data to a personal computer. The modular design of the system makes possible its modification and thus increases its adaptability to different plasma setups. Finally, the reliable operation of the entire device is confirmed by tests in Electron Cyclotron Resonance plasma.

Beschreibung: A pulsed slow-positron beam generated by an electron linear accelerator was directly used for positron annihilation lifetime spectroscopy without any positron storage devices. A waveform digitizer was introduced to simultaneously capture multiple gamma-ray signals originating from positron annihilation events during a single accelerator pulse. The positron pulse was chopped and bunched with the chopper signals also sent to the waveform digitizer. Time differences between the annihilation gamma-ray and chopper peaks were calculated and accumulated as lifetime spectra in a computer. The developed technique indicated that positron annihilation lifetime spectroscopy can be performed in a 20 μ s time window at a pulse repetition rate synchronous with the linear accelerator. Lifetime spectra of a Kapton sheet and a thermally grown SiO 2 layer on Si were successfully measured. Synchronization of positron lifetime measurements with pulsed ion irradiation was demonstrated by this technique.

Beschreibung: A major goal of nanotechnology is to develop the capability to arrange matter at will by placing individual atoms at desired locations in a predetermined configuration to build a nanostructure with specific properties or function. The scanning tunneling microscope has demonstrated the ability to arrange the basic building blocks of matter, single atoms, in two-dimensional configurations. An array of various nanostructures has been assembled, which display the quantum mechanics of quantum confined geometries. The level of human interaction needed to physically locate the atom and bring it to the desired location limits this atom assembly technology. Here we report the use of autonomous atom assembly via path planning technology; this allows atomically perfect nanostructures to be assembled without the need for human intervention, resulting in precise constructions in shorter times. We demonstrate autonomous assembly by assembling various quantum confinement geometries using atoms and molecules and describe the benefits of this approach.

Beschreibung: We developed a silicon avalanche photodiode (Si-APD) linear-array detector for use in nuclear resonant scattering experiments using synchrotron X-rays. The Si-APD linear array consists of 64 pixels (pixel size: 100 × 200 μm 2 ) with a pixel pitch of 150 μm and depletion depth of 10 μm. An ultrafast frontend circuit allows the X-ray detector to obtain a high output rate of 〉10 7 cps per pixel. High-performance integrated circuits achieve multichannel scaling over 1024 continuous time bins with a 1 ns resolution for each pixel without dead time. The multichannel scaling method enabled us to record a time spectrum of the 14.4 keV nuclear radiation at each pixel with a time resolution of 1.4 ns (FWHM). This method was successfully applied to nuclear forward scattering and nuclear small-angle scattering on 57 Fe.

Beschreibung: We describe a nanosecond time-resolved fluorescence spectrometer that acquires fluorescence decay waveforms from each well of a 384-well microplate in 3 min with signal-to-noise exceeding 400 using direct waveform recording. The instrument combines high-energy pulsed laser sources (5–10 kHz repetition rate) with a photomultiplier and high-speed digitizer (1 GHz) to record a fluorescence decay waveform after each pulse. Waveforms acquired from rhodamine or 5-((2-aminoethyl)amino) naphthalene-1-sulfonic acid dyes in a 384-well plate gave lifetime measurements 5- to 25-fold more precise than the simultaneous intensity measurements. Lifetimes as short as 0.04 ns were acquired by interleaving with an effective sample rate of 5 GHz. Lifetime measurements resolved mixtures of single-exponential dyes with better than 1% accuracy. The fluorescence lifetime plate reader enables multiple-well fluorescence lifetime measurements with an acquisition time of 0.5 s per well, suitable for high-throughput fluorescence lifetime screening applications.

Beschreibung: Diagnostic for investigating and distinguishing different laser ion acceleration mechanisms has been developed and successfully tested. An ion separation wide angle spectrometer can simultaneously investigate three important aspects of the laser plasma interaction: (1) acquire angularly resolved energy spectra for two ion species, (2) obtain ion energy spectra for multiple species, separated according to their charge to mass ratio, along selected axes, and (3) collect laser radiation reflected from and transmitted through the target and propagating in the same direction as the ion beam. Thus, the presented diagnostic constitutes a highly adaptable tool for accurately studying novel acceleration mechanisms in terms of their angular energy distribution, conversion efficiency, and plasma density evolution.

Beschreibung: μLaue diffraction with a polychromatic X-ray beam can be used to measure strain fields and crystal orientations of micro crystals. The hydrostatic strain tensor can be obtained once the energy profile of the reflections is measured. However, this remains a challenge both on the time scale and reproducibility of the beam position on the sample. In this review, we present a new approach to obtain the spatial and energy profiles of Laue spots by using a pn-junction charge-coupled device, an energy-dispersive area detector providing 3D resolution of incident X-rays. The morphology and energetic structure of various Bragg peaks from a single crystalline Cu micro-cantilever used as a test system were simultaneously acquired. The method facilitates the determination of the Laue spots’ energy spectra without filtering the white X-ray beam. The synchrotron experiment was performed at the BM32 beamline of ESRF using polychromatic X-rays in the energy range between 5 and 25 keV and a beam size of 0.5 μ m × 0.5 μ m. The feasibility test on the well known system demonstrates the capabilities of the approach and introduces the “3D detector method” as a promising tool for material investigations to separate bending and strain for technical materials.

Beschreibung: A short prototype (847-mm-long) of an Insertion Device (ID) with the dynamic compensation of ID magnetic forces has been designed, built, and tested at the Advanced Photon Source (APS) of the Argonne National Laboratory. The ID magnetic forces were compensated by the set of conical springs placed along the ID strongback. Well-controlled exponential characteristics of conical springs permitted a very close fit to the ID magnetic forces. Several effects related to the imperfections of actual springs, their mounting and tuning, and how these factors affect the prototype performance has been studied. Finally, series of tests to determine the accuracy and reproducibility of the ID magnetic gap settings have been carried out. Based on the magnetic measurements of the ID B eff , it has been demonstrated that the magnetic gaps within an operating range were controlled accurately and reproducibly within ±1 μ m. Successful tests of this ID prototype led to the design of a 3-m long device based on the same concept. The 3-m long prototype is currently under construction. It represents R&D efforts by the APS toward APS Upgrade Project goals as well as the future generation of IDs for the Linac Coherent Light Source (LCLS).

Beschreibung: A description is given of an ultra-high vacuum surface-analysis chamber that incorporates an internal cell for performing atomic layer deposition at a pressure of up to ∼1 Torr. The apparatus permits the growth process to be interrupted in stages during which data can be obtained using infrared and x-ray photoemission spectroscopies together with other electron-based techniques. Demonstration results are given for the adsorption of H 2 O on Si (100) at a pressure of ∼0.3 Torr. The system described is generally applicable in the study of any surface reaction under non-high-vacuum conditions in which there is a need for both infrared and electron spectroscopies.

Beschreibung: We recently reported the development of a high pressure electrical conductivity probe (HP-ECP) for experimental studies of formation of gas hydrates from electrolytes. The onset of the formation of methane-propane mixed gas hydrate from salt solutions was marked by a temporary upward spike in the electrical conductivity. To further understand hydrate formation a second generation of window-less HP-ECP (MkII), which has a much smaller heat capacity than the earlier version and allows access to faster cooling rates, has been constructed. Using the HP-ECP (MkII) the electrical conductivity signal responses of NaCl solutions upon the formation of ice, tetrahydrofuran hydrates, and methane–propane mixed gas hydrate has been measured. The concentration range of the NaCl solutions was from 1 mM to 3M and the driving AC frequency range was from 25 Hz to 5 kHz. This data has been used to construct an “electrical conductivity response phase diagrams” that summarize the electrical conductivity response signal upon solid formation in these systems. The general trend is that gas hydrate formation is marked by an upward spike in the conductivity at high concentrations and by a drop at low concentrations. This work shows that HP-ECP can be applied in automated measurements of hydrate formation probability distributions of optically opaque samples using the conductivity response signals as a trigger.

Beschreibung: In thermomechanical testing of hypersonic materials and structures, direct observation and quantitative strain measurement of the front surface of a test specimen directly exposed to severe aerodynamic heating has been considered as a very challenging task. In this work, a novel quartz infrared heating device with an observation window is designed to reproduce the transient thermal environment experienced by hypersonic vehicles. The specially designed experimental system allows the capture of test article's surface images at various temperatures using an optical system outfitted with a bandpass filter. The captured images are post-processed by digital image correlation to extract full-field thermal deformation. To verify the viability and accuracy of the established system, thermal strains of a chromiumnickel austenite stainless steel sample heated from room temperature up to 600 °C were determined. The preliminary results indicate that the air disturbance between the camera and the specimen due to heat haze induces apparent distortions in the recorded images and large errors in the measured strains, but the average values of the measured strains are accurate enough. Limitations and further improvements of the proposed technique are discussed.

Beschreibung: A simplified method for calibrating atomic force microscope cantilevers was recently proposed by Sader et al. [Rev. Sci. Instrum.83, 103705 (2012); Sec. III D] that relies solely on the resonant frequency and quality factor of the cantilever in fluid (typically air). This method eliminates the need to measure the hydrodynamic function of the cantilever, which can be time consuming given the wide range of cantilevers now available. Using laser Doppler vibrometry, we rigorously assess the accuracy of this method for a series of commercially available cantilevers and explore its performance under non-ideal conditions. This shows that the simplified method is highly accurate and can be easily implemented to perform fast, robust, and non-invasive spring constant calibration.

Beschreibung: There exist a number of algorithms to map the phase to amplitude in direct digital synthesis (DDS). For DDS with more than 14 output bits, the Coordinate Rotation Digital Computer (CORDIC) algorithm is well known for its high precision. Also, it is effective in solutions where there is the need of in-phase and quadrature components simultaneously because the algorithm calculates both. In this paper, a Taylor expansion based method was proposed to calculate both in-phase and quadrature at the same time. Numerical simulations for different data format, e.g., double and finite bits, were carried out in Matlab and Quartus, which were followed by the hardware implementation in Field Programmable Gate Array. The results demonstrated that the proposed method possessed higher precision and exhausted less logic elements than the CORDIC algorithm.

Beschreibung: We present a Time-to-Digital Converter (TDC) card with a compact form factor, suitable for multichannel timing instruments or for integration into more complex systems. The TDC Card provides 10 ps timing resolution over the whole measurement range, which is selectable from 160 ns up to 10 μ s, reaching 21 ps rms precision, 1.25% LSB rms differential nonlinearity, up to 3 Mconversion/s with 400 mW power consumption. The I/O edge card connector provides timing data readout through either a parallel bus or a 100 MHz serial interface and further measurement information like input signal rate and valid conversion rate (typically useful for time-correlated single-photon counting application) through an independent serial link.

Beschreibung: This paper proposes a new pulse-mixing scheme utilizing both pulse-shrinking and pulse-stretching mechanisms to improve the performance of time-to-digital converters (TDCs). The temporal resolution of the conventional pulse-shrinking mechanism is determined by the size ratio between homogeneous and inhomogeneous elements. The proposed scheme which features double-stage operation derives its resolution according to the time difference between pulse-shrinking and pulse-stretching amounts. Thus, it can achieve greater immunity against temperature and ambient variations than that of the single-stage scheme. The circuit area also can be reduced by the proposed pulse-mixing scheme. In addition, this study proposes an improved cyclic delay line to eliminate the undesirable shift in the temporal resolution successfully. Therefore, the effective resolution can be controlled completely by the pulse-mixing unit to improve accuracy. The proposed TDC composed of only one cyclic delay line and one counter is fabricated in a TSMC CMOS 0.35-μm DPQM process. The chip core occupies an extremely small area of 0.02 mm 2 , which is the best among the related works. The experimental result shows that an effective resolution of around 53 ps within ±13% variation over a 0–100 °C temperature range is achieved. The power consumption is 90 μW at a sample rate of 1000 samples/s. In addition to the reduced area, the proposed TDC circuit achieves its resolution with less thermal-sensitivity and better fluctuations caused by process variations.

Beschreibung: Real time, in situ , multiframe, diffraction, and imaging measurements on bulk samples under high and ultrahigh strain-rate loading are highly desirable for micro- and mesoscale sciences. We present an experimental demonstration of multiframe transient x-ray diffraction (TXD) along with simultaneous imaging under high strain-rate loading at the Advanced Photon Source beamline 32ID. The feasibility study utilizes high strain-rate Hopkinson bar loading on a Mg alloy. The exposure time in TXD is 2–3 μs, and the frame interval is 26.7–62.5 μs. Various dynamic deformation mechanisms are revealed by TXD, including lattice expansion or compression, crystal plasticity, grain or lattice rotation, and likely grain refinement, as well as considerable anisotropy in deformation. Dynamic strain fields are mapped via x-ray digital image correlation, and are consistent with the diffraction measurements and loading histories.

Beschreibung: We report techniques developed to utilize three-dimensional momentum information as feedback in adaptive femtosecond control of molecular dynamics. Velocity map imaging is used to obtain the three-dimensional momentum map of the dissociating ions following interaction with a shaped intense ultrafast laser pulse. In order to recover robust feedback information, however, the two-dimensional momentum projection from the detector must be inverted to reconstruct the full three-dimensional momentum of the photofragments. These methods are typically slow or require manual inputs and are therefore accomplished offline after the images have been obtained. Using an algorithm based upon an “onion-peeling” (also known as “back projection”) method, we are able to invert 1040 × 1054 pixel images in under 1 s. This rapid inversion allows the full photofragment momentum to be used as feedback in a closed-loop adaptive control scheme, in which a genetic algorithm tailors an ultrafast laser pulse to optimize a specific outcome. Examples of three-dimensional velocity map image based control applied to strong-field dissociation of CO and O 2 are presented.

Beschreibung: In order to improve the atom spin gyroscope's operational accuracy and compensate the random error caused by the nonlinear and weak-stability characteristic of the random atomic spin gyroscope (ASG) drift, the hybrid random drift error model based on autoregressive (AR) and genetic programming (GP) + genetic algorithm (GA) technique is established. The time series of random ASG drift is taken as the study object. The time series of random ASG drift is acquired by analyzing and preprocessing the measured data of ASG. The linear section model is established based on AR technique. After that, the nonlinear section model is built based on GP technique and GA is used to optimize the coefficients of the mathematic expression acquired by GP in order to obtain a more accurate model. The simulation result indicates that this hybrid model can effectively reflect the characteristics of the ASG's random drift. The square error of the ASG's random drift is reduced by 92.40%. Comparing with the AR technique and the GP + GA technique, the random drift is reduced by 9.34% and 5.06%, respectively. The hybrid modeling method can effectively compensate the ASG's random drift and improve the stability of the system.

Beschreibung: This paper describes the design and performance of an extremely low-noise differential transimpedance amplifier, which takes its two inputs from separate photodiodes. The amplifier was planned to serve as the front-end electronics for a highly sensitive shadow-displacement sensing system, aimed at detecting very low-level “Violin-Mode” ( VM ) oscillations in 0.4 mm diameter by 600 mm long fused-silica suspension fibres. Four such highly tensioned fibres support the 40 kg test-masses/mirrors of the Advanced Laser Interferometer Gravitational wave Observatory interferometers. This novel design of amplifier incorporates features which prevent “noise-gain peaking” arising from large area photodiode (and cable) capacitances, and which also usefully separate the DC and AC photocurrents coming from the photodiodes. In consequence, the differential amplifier was able to generate straightforwardly two DC outputs, one per photodiode, as well as a single high-gain output for monitoring the VM oscillations—this output being derived from the difference of the photodiodes’ two, naturally anti-phase, AC photocurrents. Following a displacement calibration, the amplifier's final VM signal output was found to have an AC displacement responsivity at 500 Hz of (9.43 ± 1.20) MV(rms) m −1 (rms), and, therefore, a shot-noise limited sensitivity to such AC shadow- (i.e., fibre-) displacements of (69 ± 13) picometres/√Hz at this frequency, over a measuring span of ±0.1 mm.

Beschreibung: We present a novel high-precision two-way optic-fiber time transfer scheme. The Inter-Range Instrumentation Group (IRIG-B) time code is modified by increasing bit rate and defining new fields. The modified time code can be transmitted directly using commercial optical transceivers and is able to efficiently suppress the effect of the Rayleigh backscattering in the optical fiber. A dedicated codec (encoder and decoder) with low delay fluctuation is developed. The synchronization issue is addressed by adopting a mask technique and combinational logic circuit. Its delay fluctuation is less than 27 ps in terms of the standard deviation. The two-way optic-fiber time transfer using the improved codec scheme is verified experimentally over 2 m to100 km fiber links. The results show that the stability over 100 km fiber link is always less than 35 ps with the minimum value of about 2 ps at the averaging time around 1000 s. The uncertainty of time difference induced by the chromatic dispersion over 100 km is less than 22 ps.

Beschreibung: Neutrons spectra from most of known sources require being collimated for numerous applications; among them one is the Neutron Activation Analysis. High energy neutrons are collimated through a mechanical procedure as one of the most promising methods. The output energy of the neutron beam depends on the velocity of the rotating Polyethylene disks. The collimated neutrons are then measured by an innovative detection technique with high accuracy.

Beschreibung: As a result of this reported research, a simulation model to analyse the behaviour of carbon nanotube field effect transistors (CNTFETs) under non-ballistic conditions is explained and the effect of gate dielectric on the performance of CNTFETs has been explored in detail. For the first time, a thorough study of the combined non-ballistic effect on the performance of CNTFETs has been conducted and the output of the device has been analysed. It has been observed that a gate material with a high dielectric constant leads to higher on-state current and higher on and off state current ratio. In addition, the transconductance, total capacitance, charging energy, subthreshold swing ( S ), drain-induced barrier lowering (DIBL) and gain with respect to the dielectric constant have been observed and analysed. Transconductance and total capacitance increases by a significant amount, while charging energy and S decrease as the dielectric value increases. The DIBL and gain vary slightly as a higher value dielectric material is used as a gate. Furthermore, the results of this study have been plotted against previously reported ballistic outputs to provide a better perception of the deviation from ideal behaviour. At the same time, the outcomes of this analysis have been compared against some reported experimental values.

Beschreibung: An investigation has been conducted into the electron transport properties in carbon nanotube (CNT)–graphene contacts with a fully non-equilibrium Green's functions method combined with the density functional theory. Four different models are considered, where the contact geometries are varied. Their similar electron transmission characteristics are demonstrated with little dependence on the contact conditions at high energy and considerable dependence at low energy. The vacuum gap hinders the electron transport, resulting in an additional contact barrier. The electron transmission is mainly performed between the boundary carbon atoms of the CNT and the nearest graphene atoms, and the imperfection of the edge carbon atoms in a hexagonal lattice destroys the ballistic transport in graphene and the CNT at the contact. The current–voltage characteristics are presented as well. This reported work gives an insight into the electronic transport properties of the contacts and suggests that graphene is a suitable electrode material for applications in full-CNT devices.

Beschreibung: In this reported work, the extinction coefficient of water-based nanofluids containing multi-walled carbon nanotubes (MWNCTs) has been experimentally measured. The MWCNTs were dispersed in deionised water with a surfactant, hexadecyltrimethyl-ammonium bromide, and they were homogenised by a bath-type ultrasonicator and a mechanical stirrer. The characteristics of MWCNTs suspended in the nanofluids were examined by transmission electron microscopy and scanning electron microscopy images and their hydrodynamic particle size was measured by a particle size analyser. The extinction coefficient of nanofluids was measured by an in-house developed apparatus at a single wavelength (632.8 nm) based on the Lambert-Beer principle. With the experimentally obtained extinction coefficient, the efficiency of a flat-plate type direct-absorption solar collector (DASC) was theoretically estimated. For this purpose, a modified analytical solution of the DASC efficiency is presented by assuming that the extinction coefficient is not a function of the wavelength. Finally, the efficiency of DASC is demonstrated according to the nanotube volume fractions. The results show that the DASC concept can further improve the efficiency of the conventional flat-plate type solar collectors.

Beschreibung: A micromachined cantilever-based flow sensor is designed based on differential pressure. Numerical analysis and analogue simulation are used to investigate the FSI (fluid–structure interaction) characteristics of the differential pressure flow sensor. The FSI model is created using the hydromechanics and elastic mechanics, and a systematic theory is established to complete the numerical analysis. Then the working mechanism of the flow sensor is analysed depending on the FSI results. The analogue simulation is undertaken by the commercial software FLUENT and ANSYS. The result of the numerical analysis is similar to that of the analogue simulation. Considering the results of the numerical analysis and the analogue simulation, the shape and size of the flow sensor are optimised. Moreover, the optimised flow sensor is fabricated and calibrated. The calibration results show that the cantilever-based differential pressure flow sensor achieves ideal static characteristics and works well in practical applications.

Beschreibung: A microresonant accelerometer which consists of silicon substrate and a quartz double-ended tuning fork (DETF) is described. A temperature isolator structure on the silicon substrate is designed to decrease the influence of thermal stress on the DETF's tines. Two stiff ends of the quartz DETF are mounted on the proof mass and temperature isolator, respectively. When acceleration is applied, the proof mass will move, inducing the variation of axial stress on the DETF's tines. The resonance frequency of the DETF's tines will change corresponding to the stress, so acceleration can be measured. The DETF is excited by the inherent piezoelectric property of quartz based on the anti-phase in-plane bending model. Both the silicon substrate and the DETF are fabricated by micromachining. The sensor is analysed by finite-element simulation. According to the simulation, the temperature isolator decreases thermal stress by 30.2%. Experimental results show that the resonance frequency of the sensor is 35.2563 kHz and the sensitivity is 8.55 Hz/ g , which is in good agreement with analytical calculation.

Beschreibung: A highly applicable theoretical model and a simple, inexpensive mould-based method is introduced to design and fabricate the pyramid-shaped SU-8 microneedle. The main purpose is to be able to extract blood at point-of-care sites from up to 80% of typical nurse-home patients with a disorder of blood circulation in fingers and toes (Raynaud's phenomenon). Geometry optimisation was conducted based on the study of fracture force, which can be accurately predicted by the proposed theoretical model. The accuracy of the proposed theoretical model was confirmed by the finite element study and practical measurement. For practical verification, measurement of fracture force was conducted on fabricated SU-8 microneedles, including a 1470 µm-tall pyramid-shaped microneedle and a 1515 µm-tall traditional-shaped microneedle. The measurement results confirmed the improved strength of the proposed pyramid-shaped microneedle, especially of the pyramidal tips, which can exhibit significantly higher applied force with 2.82 N compared with the 0.51 N bevel tip. Practical tests of skin penetrability on human fingers showed that the microneedles fabricated with the proposed geometry may be sharp and strong enough to safely puncture human skin and long enough to reach the blood vessels.

Beschreibung: A fabrication process of silicon hierarchical nanopillar arrays (NPAs) based on the self-assembled colloid particle monolayer is presented. Using colloid particles assembled by the evaporation-induced method as masks, well-ordered silicon NPAs were fabricated by assessing the deep reactive ion etching process. After the optimisation of the cycles of etching and passivation steps, double-layer hierarchical NPAs were achieved simultaneously. Systematic analysis and experiments were conducted to investigate the transition from well-ordered silicon NPAs to silicon hierarchical NPAs. An explanation of this transition is provided based on the collapsing phenomenon discovered in the experiments.

Beschreibung: A unique approach for the fabrication of long-aspect ratio microtubes is presented for an antimatter trap. Conventionally, non-neutral antimatter is stored using a Penning-Malmberg trap, a single tube with aspect ratios being of the order of less than 10:1. Parallel microtubes with aspect ratios of 1000:1 have the potential to store many orders of magnitude more. The silicon industry has paved the way to microelectromechanical systems technologies which have been utilised in this research. Standard processes such as photolithography, deep reactive ion etching, sputtering and thermo-compression bonding were all used; however, unique methods of these processes were developed to overcome many engineering challenges and realise successful trapping.

Beschreibung: A dual-band microbolometer coupled with an H-shaped fractal antenna, which can detect both infrared (IR) and THz waves simultaneously is proposed. Firstly, the H-shaped fractal antenna for 125 and 500 μm dual-bands is proposed by using the dipole antenna formula and finite element method (FEM) simulation. On the basis of simulation results, the H-shaped fractal antenna for the microbolometer is fabricated and the electromagnetic wave absorption characteristics of it are measured. Transmission measurement successfully confirmed the absorption peaks near the aimed for two wavelengths in the IR and THz regions, respectively. It showed that the proposed microbolometer coupled with the H-shaped fractal antenna is considered as a useful tool for widely separated multi-band detection. Moreover, for the microbolometer design, the influence of bias line resistivity on microbolometer characteristics with two different bias line materials by the FEM simulation is studied. It is observed that the electromagnetic wave absorption characteristics of the microbolometer are affected by the resistivity of the bias line material, especially when the parallel polarised incident wave to the bias line formation direction is irradiated.

Beschreibung: To investigate the mechanical strength of the anchor–microbeam combined structure, two series of devices (bonding quality testing devices and torsional strength testing devices) are designed and fabricated by the silicon-on-glass process. A novel array-shaped anchor scheme is presented, which has been compared with the conventional single anchor. The experimental results have shown that the bonding quality of the anchor degenerated severely when the bonding area became very small (〈400 μm 2 ). The testing results of bonding quality testing devices demonstrated that the presented array-shaped anchor design helped to improve the anodic bonding yield. According to the bending fracture test of the torsional strength testing devices, the array-shaped anchor design had an almost equal torsional strength compared with the single anchor with the same occupied area. Moreover, the torsional strength of the array-shaped anchor was even greater when the bonding area was the same. In the fracture test, the fracture would happen in the anchor since the structure size was small. When the structure was larger, the fracture happened in the cantilever beam, rather than the anchor.

Beschreibung: A new enabling technology for low-cost high throughput parallel scanning probe nanolithography is presented. Monolithic integration of microelectromechanical systems (MEMS) actuators with two-dimensional probe arrays as well as preliminary results in the simultaneous generation of multiple submicron patterns using such structures is reported. Two-degree-of-freedom electrothermal MEMS positioning structures integrated with nanoscale probe-tips are used to perform parallel scanning probe nanolithography circumventing the main deficiency of tip-based nanolithography, that is, low throughput. Simultaneous generation of multiple patterns scratched into 800 nm thick photoresist and 200 nm thick gold layers has been successfully demonstrated. Scratch marks as narrow and as long as ∼50 and 27 µm, respectively, have been generated in the X and Y directions using two different microactuator structures carrying 10 and 64 nanotips.

Beschreibung: Conventional metal microparts were fabricated by a series of complex photolithography, sputtering, sacrificial layer and release processes. This reported work demonstrates the integrated process of metal microparts using 1064 nm Nd:YVO 4 laser direct-write patterning of indium tin oxide (ITO) thin films on glass, followed by the electrochemical deposition of copper (Cu) on the pattern. The ITO thin film could be removed without any damage to the glass structure through the diffractive multiple Nd:YVO 4 beam. A high overlapping area of the laser spot was used to pattern the electrode layer on the film surface for obtaining a 50 µm ablated edge profile with a linear boundary after laser patterning. A high quality of surface could be achieved at a proper parameter control without numerous processing steps. Compared with conventional photolithography and etching technologies, direct-write micropatterns of ITO using the Nd:YVO 4 laser is a maskless, dry and low-cost process. Accordingly, the micrometal parts can be obtained using the electrochemical deposition and release process of laser-patterned ITO films because of the adhesion property of Cu on ITO.

Beschreibung: Presented is the configuration design for piezoresistive absolute micropressure sensors. A figure of merit called the performance factor (PF) is defined as a quantitative index to describe the comprehensive performances of a sensor including sensitivity, resonant frequency and acceleration interference. Two configurations are proposed through introducing islands and sensitive beams into the typical flat diaphragm. The stress distributions of sensitive elements are analysed by a finite element method. Multivariate fittings based on ANSYS simulation results are performed to establish the equations on surface stresses and deflections of the two sensors. Optimisation by MATLAB is carried out to determine the dimensions of the configurations. Convex corner undercutting is analysed to estimate the final dimensions of the islands. Each PF of the two configurations with the determined dimensions has been calculated and compared. Silicon bulk micromachining is utilised to fabricate the prototypes of the sensors. The outputs of the sensors under both static and dynamic conditions are tested. Experimental results reveal that the configuration with quad islands presents the highest PF of 210.947 Hz 1/4 . The favourable overall performances make the sensor more suitable for altimetry.

Beschreibung: The fabrication and use of silicon nanowire (SiNW) array-patterned microcantilever sensors for enhancing aerosol mass detection are described. Surface modification of the cantilever is performed selectively by combining the processes of nanoimprint lithography, photolithography and inductively coupled plasma cryogenic reactive ion etching. Cylindrical wire structures of 300 nm diameter with aspect ratios of 3–7 can be realised for the current SiNWs, which can be altered depending on the nanoimprint stamp size and etching recipe. Owing to the rise in the collection surface area of the sensor provided by vertical SiNWs, an increase of aerosol sampling efficiency can be obtained during cigarette smoke exposure, which is a factor of 1.5 higher than that of a corresponding plain cantilever. This proposed structure is intended to be used as a sensor module of a personal aerosol mass detector.

Beschreibung: Inspired by the anisotropy of the rice leaf surface, high-speed wire electrical discharge machining (HS-WEDM) technology was used to build submillimetre-scale structures on the 304 stainless steel surfaces, and fluorination treatment was applied on the resulting surfaces. The wettability and microstructure of the resulting surfaces were investigated by a large depth 3D scanner, scanning electron microscopy and by the contact angle measuring instrument. The durability of the fabricated surface was evaluated by wear tests. Results show that the V-shaped groove arrays with a hierarchical structure on the processed surfaces are built by HS-WEDM. After the fluorination treatment, the as-machined surfaces show good one-direction superhydrophobicity and the obvious two-direction (the parallel and perpendicular groove directions) anisotropic wettability. The effect of the size of the V-shaped groove on the two-direction anisotropy is discussed. The wear tests show that the one-direction superhydrophobicity and the two-direction anisotropic sliding properties of the stainless steel surfaces are still exhibited after the tests. Fabricating rough surfaces by HS-WEDM is efficient and does not require complex process operation and large area three-dimensional features. This method can realise industrial production.

Beschreibung: A novel manufacturing method of fabricating nanochannels with complex three-dimensional (3D) structures based on a modified atomic force microscopy (AFM) nanoscratching method is presented. By changing the moving trajectories of the AFM tip, arbitrary geometric patterns were obtained. Nanochannels consisting of the superposition of geometric figures could be fabricated through extensively controlling the scanning velocity of the AFM tip and combining the movement of the AFM tip with the high-precision stage. Machining experiments were performed to demonstrate the capability, validity and flexibility of the proposed approach. Finally, nanochannels with complex 3D structures were presented in an automated, flexible but cost-effective way.

Beschreibung: Polylactic acid (PLA) was blended with polyethylene glycol (PEG) and spun via a melt-electrospinning system. The effect of PEG content on the PLA melt and the thermal behaviour of the blend was studied using dynamic rheometry and differential scanning calorimetry, respectively. By fitting a rheological model, parameters such as zero-shear viscosity and the relaxation time of polymer chains were obtained. A substantial reduction of zero-shear viscosity and relaxation time by increasing the PEG content from 0 to 30 wt% was observed. Crystallisation peaks shifted to lower temperatures and the crystallinity level increased in PLA/PEG blends against PEG concentration. The results revealed enhanced polymer chain mobility because of the plasticising effect of PEG. Continuous microfibres were obtained by electrospinning of PLA/PEG blends. While neat PLA was not spinnable at the spinning temperature of 200°C, PLA/PEG blends were easily spun and the lowest fibre diameters of 3–6 μm were achieved with 30% PEG loading, at an applied voltage of 70 kV.

Beschreibung: Silver (Ag) nanosheets were synthesised through a facile self-seeding strategy with binary reduction in the poly(vinylpyrrolidone) (PVP)–sodium dodecyl sulphate (SDS) aggregation microreactor, in which the size and morphology of Ag nanoparticles were able to be regulated by concentration or pH dependence. In this approach, PVP and SDS built the microreactor together and served as a synthesis template; a trace of sodium borohydride (NaBH 4 ) was employed to rapidly trigger the competitive formation of small Ag seeds, while PVP was responsible for the subsequent reduction and slow crystal growth. The size and morphology of the nanosheets could be gently regulated with the concentrations of PVP or SDS and the pH of the reaction solution; while the dramatic variance of size and morphology was primarily induced by NaBH 4 concentration. Free PVP monomers with lower concentration induced irregular particles, while the lower concentration of NaBH 4 led to the formation of small and regular nanosheets. Both particle size and morphology could be regulated with SDS concentration dependence if the SDS concentration was higher than the critical aggregation concentration. Higher SDS concentrations favoured smaller particle sizes and nanosheet formation. Two-dimensional planar Ag nanostructures were generated at pH 9–10, where [Ag(NH 3 ) 2 ] + existed at a stable complex ionisation state.

Beschreibung: Nanocadmium sulphide (CdS) has been prepared by the one-pot solid-state method from cadmium chloride (CdCl 2 ) and sodium sulphide (Na 2 S) without any capping agent. The grinding period plays a major role in transforming CdS from the cubic (zinc blende) to the hexagonal (wurtzite) phase, hitherto unreported at the lowest temperature of 200°C by the solid-state approach. The compounds are characterised by powder X-ray diffraction, UV–visible absorption spectroscopy, scanning electron microscopy and high resolution transmission electron microscopy techniques. On the basis of the results, it has been observed that with only grinding and without subsequent heat treatment, the compounds named with their grinding period as subscript have either zinc blende – CdS (30 min) or mixed zinc blende/wurtzite – CdS (2,4, 6 and 8 h) structures. However, when subjected to heat treatment at 200°C, there is a complete phase transformation to the wurtzite structure achieved only with the CdS (8 h) compound, while the rest of the compounds show similar phases as the compounds prepared without annealing. The photocatalytic efficiency of CdS compounds on methyl orange follows the order, CdS (cubic) 〉 CdS (mixed phase → cubic + hexagonal) 〉 CdS (hexagonal) , with cubic phase CdS showing greater efficiency than mixed and hexagonal phases.

Beschreibung: In this reported work, Mn 3 O 4 octahedron submicrostructures (Mn 3 O 4 OSMs) were obtained through a facile solvothermal method in mixed solvent. The authors have modified a glassy carbon electrode (GCE) with Mn 3 O 4 OSMs and Nafion to obtain a sensing platform (Mn 3 O 4 OSMs/Nafion/GCE) for the non-enzymatic detection of H 2 O 2 . The resulting Mn 3 O 4 OSMs/Nafion/GCE exhibited good electrochemical catalytic activity towards the reduction of H 2 O 2 in a phosphate buffered solution (0.1 M, pH = 7.0). The linear detection range was estimated to be in the range from 5 µM to 17 mM ( R = 0.9998), and the detection limit was estimated to be 1.5 µM at S / N = 3. Real sample analyses show that the sensor developed in this work could be efficiently used for the determination of H 2 O 2 .

Beschreibung: Demand has increased for the double-sided moulding of microfluidic devices for a series of biochemical analyses. Accurate alignment of mould inserts is a critical aspect to transfer doubled-sided patterns on the top and bottom surfaces of a moulded part. A method of mould alignment was studied for double-sided hot embossing of polymer microfluidic devices. An alignment method was designed using kinematic constraints, and a set of three locating pins. To validate the alignment method, two brass mould inserts with fluidic reservoirs were used for the double-sided moulding of prototype microfluidic devices. The kinematic constraints were used to align the mould inserts with each other on the hot embossing machine. The misalignment of double-sided features on the moulded parts was measured using a measuring microscope. The X - and Y -magnitudes of the mismatches ranged from −28 to 118 µm along the X -axis of the moulded parts. The X - and Y -magnitudes of the mismatches along the Y -axis of the moulded parts varied from −38 to 141 µm. The results of the experiments showed that the mould alignment using kinematic constraints is applicable to the fabrication of double-sided patterns for microfluidic devices.

Beschreibung: Monodisperse α-Fe 2 O 3 nanocubes with a mean size of 85 nm have been prepared by heating an aqueous solution of iron (III) nitrate in the presence of a certain amount of alkali without any additional organic reagents or templates in a hydrothermal route. The structure and morphology of the products were characterised by X-ray diffraction, transmission electron microscopy and field-emission scanning electron microscopy. The results have shown that the crystal morphology continually changes at higher temperatures and α-FeOOH was generated as the intermediate during the hydrothermal dehydration reaction. In addition, the optimum temperature and reaction time of the hydrothermal synthesis of these α-Fe 2 O 3 nanocubes were 200°C and 5 h, respectively.

Beschreibung: Silver nanoparticles were synthesised successfully using poly(2-acrylamido-2-methylpropane sulphonic acid) (PAMPS) as a surfactant. Silver nanoparticles prepared through this approach possess high purity and narrow size distribution. The size distribution result shows that the diameters ranging from 78.82 to 105.709 nm can account for 76.41% of nanoparticles. UV–vis spectra were used to record the formation of silver nanoparticles in detail. It is found that PAMPS can play an important role in the formation and the colloidal stabilisation of silver nanoparticles because of the high affinity of sulphonic and amide with silver ions. The formation is summarised in detail. In addition, a potential application in nanocomposites of this method is explored. The Ag/polyaniline (PANI) nanocomposite prepared using this method shows higher electrical conductivity than that prepared using other methods. This method is novel, convenient, efficient and environmental-friendly, especially suiting those wastewaters treatment facilities containing silver ions. At the same time, it is also promising to prepare Ag/PANI or other metals/polymer composites via in-situ polymerisation.

Beschreibung: It is demonstrated that it is possible to switch the magnetisation of nanomagnets by employing the exchange interaction between magnets. This can implement on-chip clocking for nanomagnetic logic circuits by using a current-carrying copper wire circularly wrapped by ferromagnetic cladding. This scheme is potentially more energy efficient than yoked cladding clocking using an external magnetic field for magnetisation switching. Maxwell simulation shows that current flowing through copper wire can be reduced by about one hundred times compared with yoked clocking, which means power consumption could be lowered by 10 4 times. Micromagnetic simulation shows that the nanomagnetic chain aligned on the proposed clocking can achieve a correct functional state.

Beschreibung: Molecular dynamics simulations and micromechanics model analysis are performed to investigate the mechanical behaviours and interfacial effects of interpenetrating phase composites in the nanoscale. It is observed that the overall Young's modulus and ultimate strength of the nanocomposites vary nonlinearly with the cohesive energy of the interface. The cohesive properties affect the stiffness of the interface zone, and in turn, influence the effective Young's modulus of composites. The competition between interfacial failure and weak phase damage results in an optimal cohesive parameter of the interface, at which the composite possesses the maximal ultimate strength. The obtained results provide useful guidelines for the design and optimisation of advanced nanocomposites with superior mechanical properties.

Beschreibung: Poly(o-aminophenol) (POAP)/multi-walled carbon nanotube (MWCNT) nanocomposite and POAP in the absence of the MWCNT were fabricated by consecutive cyclic voltammetry (CV) on a graphite (G) electrode. The dispersion of nickel (II) ions was accomplished and incorporated into the polymeric electrodes (G/POAP and G/POAP-MWCNT) by immersing them into a 0.1 M nickel (II) solution. Following preparation of G/POAP/Ni and G/POAP-MWCNT/Ni, the electrochemical behaviour was examined using CV. Scanning electron microscopy was used for characterisation of the nanocomposite. The prepared electrodes showed enhanced electrocatalytic activity for the oxidation of acetaminophen and facilitated the detection of acetaminophen in a 0.1 M NaOH solution. Compared with the G/POAP/Ni electrode, the G/POAP-MWCNT/Ni electrode had a significant current response of acetaminophen oxidation because of the synergistic effects of POAP and the MWCNT. By CV, the calibration plot was linear in the range of 1–13 mM with standard deviation between 0.3 and 6.54% for acetaminophen. The G/POAP-MWCNT/Ni was successfully applied for acetaminophen determination in tablets and the results showed sufficient precision and achieved a mean recovery of 96.8% (R.S.D. = 4.9%).

Beschreibung: A series of novel colourful BiOI photocatalysts have been synthesised by a simple oil bath method at 160°C. Several characterisation tools including X-ray diffraction, a scanning electron microscope, energy-dispersive X-ray spectroscopy and ultraviolet–visible diffuse reflectance spectroscopy were used to study the phase structure, morphologies, bandgap and catalytic performance of the prepared samples. The results show that BiOI exhibited higher photocatalytic efficiency under visible light ( λ 〉 420 nm) in the degradation of methyl orange. This result could be because of the narrow bandgap, for which E g is about 1.4–2.25 eV, and a number of active positions for catalysts. h + acts as the main active species during methyl orange degradation.

Beschreibung: The silica (SiO 2 ) sol and hybrid zirconia (ZrO 2 )/SiO 2 sol were used to coat cotton fabrics using the pad-dry-cure method to improve their physical and functional properties. The physical properties of coated and uncoated fabrics, such as tensile strength, tear strength, crease recovery angle, air permeability and whiteness index, were tested as per the standard test methods. The wash durability of the coating on the fabric was also analysed after five and 10 wash cycles. The observed results show that the ZrO 2 /SiO 2 -coated fabric has better physical properties than SiO 2 -coated and uncoated fabrics. In addition, an antibacterial activity test confirms that the SiO 2 -coated fabric possesses higher antibacterial properties against Escherichia coli and Staphylococcus aureus than the ZrO 2 /SiO 2 -coated fabrics.

Beschreibung: An easy approach for the fabrication of titanium dioxide hollow spheres is proposed. Nanostructures were obtained by the conventional hard template method with silica-protected calcination. The samples were characterised by differential thermal analysis and thermogravimetry, Brunauer-Emmett-Teller nitrogen adsorption isotherms, X-ray diffraction, scanning and transmission electron microscopy (SEM and TEM). Raman spectroscopy and optical properties of the prepared materials were studied as well. X-ray analysis has shown that the silica protection layer allows direct phase transformation from amorphous titania to crystalline anatase regardless of the temperature. The crystallite size is more than 5 nm. The diameter of the obtained hollow nanostructures is within the range 115–420 nm. The thickness of the walls varies from 12 to 38 nm depending on annealing conditions. TEM and SEM images confirm their spherical shape.

Beschreibung: Acceleration in development of additional conventional hydropower requires tools and methods to perform laboratory and in-field validation of turbine performance and fish passage claims. The new-generation Sensor Fish has been developed with more capabilities to accommodate a wider range of users over a broader range of turbine designs and operating environments. It provides in situ measurements of three-dimensional (3D) linear accelerations, 3D rotational velocities, 3D orientation, pressure, and temperature at a sampling frequency of 2048 Hz. It also has an automatic floatation system and built-in radio-frequency transmitter for recovery. The relative errors of the pressure, acceleration, and rotational velocity were within ±2%, ±5%, and ±5%, respectively. The accuracy of orientation was within ±4° and accuracy of temperature was ±2 °C. The new-generation Sensor Fish is becoming a major technology and being deployed for evaluating the conditions for fish passage of turbines or other hydraulic structures in both the United States and several other countries.

Beschreibung: High-speed atomic force microscopy has attracted much attention due to its unique capability of visualizing nanoscale dynamic processes at a solid/liquid interface. However, its usability and resolution have yet to be improved. As one of the solutions for this issue, here we present a design of a high-speed Z -tip scanner with screw holding mechanism. We perform detailed comparison between designs with different actuator size and screw arrangement by finite element analysis. Based on the design giving the best performance, we have developed a Z tip scanner and measured its performance. The measured frequency response of the scanner shows a flat response up to ∼10 kHz. This high frequency response allows us to achieve wideband tip-sample distance regulation. We demonstrate the applicability of the scanner to high-speed atomic-resolution imaging by visualizing atomic-scale calcite crystal dissolution process in water at 2 s/frame.

Beschreibung: A suspension system of classical geophone was developed, adopting multiple pairs of leaf springs as a substitute for one pair. The finite element analysis was used as the solving means, and the results indicated that the geophone performance with developed suspension system was more favorable than that with conventional suspension system. First, the operating broadband of the improved geophone was wider than that of the conventional geophone. Second, the distortion of output signal for a geophone was slightly reduced, which was usually enlarged with improving the ratio of spurious resonant frequency to natural frequency.

Beschreibung: A liquid membrane electrochemical etching process for preparing nano-tips is proposed by the introduction of buoyant force to the lower tip, in which the lower portion of the anodic wire is immersed into a floating layer. A mathematical model of this method is derived. Both calculation and experimental results demonstrate that the introduction of buoyant force can significantly decrease the tip radius. The lubricating oil and deionized water floating layers were tested for the processing of nano-tips. Further, high-aspect-ratio nano-electrodes were prepared by applying a relative vertical movement to the anodic wire.

Beschreibung: Construction and characterization of a multichannel photodiode detector based on commercially available components with high signal to noise of ∼10 6 and a rapid frame rate, suitable for time resolved femtosecond spectroscopy with high repetition femtosecond sources, is presented.

Beschreibung: The neutron imaging system at the National Ignition Facility (NIF) is an important diagnostic tool for measuring the two-dimensional size and shape of the neutrons produced in the burning deuterium-tritium plasma during the stagnation stage of inertial confinement fusion implosions. Since the neutron source is small (∼100 μ m) and neutrons are deeply penetrating (〉3 cm) in all materials, the apertures used to achieve the desired 10- μ m resolution are 20-cm long, triangular tapers machined in gold foils. These gold foils are stacked to form an array of 20 apertures for pinhole imaging and three apertures for penumbral imaging. These apertures must be precisely aligned to accurately place the field of view of each aperture at the design location, or the location of the field of view for each aperture must be measured. In this paper we present a new technique that has been developed for the measurement and characterization of the precise location of each aperture in the array. We present the detailed algorithms used for this characterization and the results of reconstructed sources from inertial confinement fusion implosion experiments at NIF.

Beschreibung: Laser-based time-domain thermoreflectance (TDTR) and frequency-domain thermoreflectance (FDTR) techniques are widely used for investigating thermal transport at micro- and nano-scales. We demonstrate that data obtained in TDTR measurements can be represented in a frequency-domain form equivalent to FDTR, i.e., in the form of a surface temperature amplitude and phase response to time-harmonic heating. Such a representation is made possible by using a large TDTR delay time window covering the entire pulse repetition interval. We demonstrate the extraction of frequency-domain data up to 1 GHz from TDTR measurements on a sapphire sample coated with a thin layer of aluminum, and show that the frequency dependencies of both the amplitude and phase responses agree well with theory. The proposed method not only allows a direct comparison of TDTR and FDTR data, but also enables measurements at high frequencies currently not accessible to FDTR. The frequency-domain representation helps uncover aspects of the measurement physics which remain obscured in a traditional TDTR measurement, such as the importance of modeling the details of the heat transport in the metal transducer film for analyzing high frequency responses.

Beschreibung: The ability to synchronize a femtosecond laser to x-ray pulses is crucial for performing ultrafast time-resolved x-ray scattering experiments at synchrotrons. Conventionally, the task has been achieved by locking a harmonic frequency of the laser oscillator to the storage ring master radio-frequency (RF). However, when the frequency mismatch between the two sources cannot be compensated by small adjustments to the laser cavity length, synchronization to a harmonic frequency requires modifying the optical components of the laser system. We demonstrate a novel synchronization scheme, which is a flexible alternative for synchronizing these two sources operating at arbitrarily different frequencies. First, we find the greatest common divisor (GCD) of the two frequencies that is still within the limited tuning range of the laser cavity length. The GCD is generated by dividing down from the storage ring RF, and is separately multiplied up to provide a feedback signal for synchronizing the laser cavity. Unique to our scheme, the GCD also serves as a harmonic RF source for the laser amplifier such that only laser oscillator pulses at fixed integer multiples of the storage ring RF are selected for amplification and delivery to experiments. Our method is implemented at the Photon Test Facility beamline of Pohang Light Source where timing-jitter less than 4 ps (r.m.s.) is measured using a new shot-to-shot method.

Beschreibung: A semi-adiabatic isoperibol solution calorimeter has been indigenously developed. The measurement system comprises modules for sensitive temperature measurement probe, signal processing, data collection, and joule calibration. The sensitivity of the temperature measurement module was enhanced by using a sensitive thermistor coupled with a lock-in amplifier based signal processor. A microcontroller coordinates the operation and control of these modules. The latter in turn is controlled through personal computer (PC) based custom made software developed with LabView. An innovative summing amplifier concept was used to cancel out the base resistance of the thermistor. The latter was placed in the dewar. The temperature calibration was carried out with a standard platinum resistance (PT100) sensor coupled with an 8½ digit multimeter. The water equivalent of this calorimeter was determined by using electrical calibration with the joule calibrator. The experimentally measured values of the quantum of heat were validated by measuring heats of dissolution of pure KCl (for endotherm) and tris (hydroxyl methyl) amino-methane (for exotherm). The uncertainity in the measurements was found to be within ±3%.

Beschreibung: A biomedical microwave tomography system with 3D-imaging capabilities has been constructed and translated to the clinic. Updates to the hardware and reconfiguration of the electronic-network layouts in a more compartmentalized construct have streamlined system packaging. Upgrades to the data acquisition and microwave components have increased data-acquisition speeds and improved system performance. By incorporating analog-to-digital boards that accommodate the linear amplification and dynamic-range coverage our system requires, a complete set of data (for a fixed array position at a single frequency) is now acquired in 5.8 s. Replacement of key components (e.g., switches and power dividers) by devices with improved operational bandwidths has enhanced system response over a wider frequency range. High-integrity, low-power signals are routinely measured down to −130 dBm for frequencies ranging from 500 to 2300 MHz. Adequate inter-channel isolation has been maintained, and a dynamic range 〉110 dB has been achieved for the full operating frequency range (500–2900 MHz). For our primary band of interest, the associated measurement deviations are less than 0.33% and 0.5° for signal amplitude and phase values, respectively. A modified monopole antenna array (composed of two interwoven eight-element sub-arrays), in conjunction with an updated motion-control system capable of independently moving the sub-arrays to various in-plane and cross-plane positions within the illumination chamber, has been configured in the new design for full volumetric data acquisition. Signal-to-noise ratios (SNRs) are more than adequate for all transmit/receive antenna pairs over the full frequency range and for the variety of in-plane and cross-plane configurations. For proximal receivers, in-plane SNRs greater than 80 dB are observed up to 2900 MHz, while cross-plane SNRs greater than 80 dB are seen for 6 cm sub-array spacing (for frequencies up to 1500 MHz). We demonstrate accurate recovery of 3D dielectric property distributions for breast-like phantoms with tumor inclusions utilizing both the in-plane and new cross-plane data.

Beschreibung: In situ x-ray absorption spectroscopy (XAS) provides element-specific characterization of both crystalline and amorphous phases and enables direct correlations between electrochemical performance and structural characteristics of cathode and anode materials. In situ XAS measurements are very demanding to the design of the experimental setup. We have developed a sample chamber that provides electrical connectivity and inert atmosphere for operating electrochemical cells and also accounts for x-ray interactions with the chamber and cell materials. The design of the sample chamber for in situ measurements is presented along with example XAS spectra from anode materials in operating pouch cells at the Zn and Sn K-edges measured in fluorescence and transmission modes, respectively.

Beschreibung: The light intensity of 6 Li III line spectrum at λ = 516.7 nm was observed during 6 Li 3+ beam tuning at the Hyper-Electron Cyclotron Resonance (ECR) ion source. Separation of ion species of the same charge to mass ratio with an electromagnetic mass analyzer is known to be an exceptionally complex process. However, 6 Li III line intensity observation conducted in this study gives new insights into its simplification of this process. The light intensity of 6 Li III line spectrum from the ECR plasma was found to have a strong correlation with the extracted 6 Li 3+ beam intensity from the RIKEN Azimuthal Varying Field cyclotron.

Beschreibung: The paper describes a time- and angle-resolved photoemission apparatus consisting of a hemispherical analyzer and a pulsed laser source. We demonstrate 1.48-eV pump and 5.92-eV probe measurements at the ⩾10.5-meV and ⩾240-fs resolutions by use of fairly monochromatic 170-fs pulses delivered from a regeneratively amplified Ti:sapphire laser system operating typically at 250 kHz. The apparatus is capable to resolve the optically filled superconducting peak in the unoccupied states of a cuprate superconductor, Bi 2 Sr 2 CaCu 2 O 8 + δ . A dataset recorded on Bi(111) surface is also presented. Technical descriptions include the followings: A simple procedure to fine-tune the spatio-temporal overlap of the pump-and-probe beams and their diameters; achieving a long-term stability of the system that enables a normalization-free dataset acquisition; changing the repetition rate by utilizing acoustic optical modulator and frequency-division circuit.

Beschreibung: Ellipsometry is one of the standard methods for observation of glass transition in thin polymer films. This work proposes that sensitivity of the method to surface morphology can complicate manifestation of the transition in a few nm thick samples. Two possible mechanisms of free surface roughening in the vicinity of glass transition are discussed: roughening due to lateral heterogeneity and roughening associated with thermal capillary waves. Both mechanisms imply an onset of surface roughness in the glass transition temperature range, which affects the experimental data in a way that shifts apparent glass transition temperature. Effective medium approximation models are used to introduce surface roughness into optical calculations. The results of the optical modeling for a 5 nm thick polystyrene film on silicon are presented.

Beschreibung: Investigations of emission of harmonics from argon gas jet irradiated by 700 fs, 5 mJ pulses from a KrF laser are presented. Harmonics conversion was optimized by varying the experimental geometry and the nozzle size. For the collection of the harmonic radiation silicon and solar-blind diamond semiconductor detectors equipped with charge preamplifiers were applied. The possibility of using a single-crystal CVD diamond detector for separate measurement of the 3rd harmonic in the presence of a strong pumping radiation was explored. Our experiments show that the earlier suggested 0.7% conversion efficiency can really be obtained, but only in the case when phase matching is optimized with an elongated gas target length corresponding to the length of coherence.

Beschreibung: The RF properties of an accelerating structure, and the pulse structure and charge per bunch in the electron beam propagating through it are important parameters that determine the impact of beam loading in the structure. The injector linac of the Compact Ultrafast Terahertz Free-Electron Laser (CUTE-FEL) has been operated with two different pulse structures during initial commissioning experiments and the effect of beam loading on the accelerated electron beam parameters has been studied analytically for these two pulse structures. This paper discusses the analytical study of beam loading in a Standing Wave, Plane Wave Transformer linac employed in the CUTE-FEL setup, and a possible technique for its compensation for the electron beam parameters of the CUTE-FEL. A parametric study has been performed to study beam loading for different beam currents and to optimize injection time of the electron beam to compensate beam loading. Results from the parametric study have also been used to explain previously observed results from acceleration experiments in the CUTE-FEL setup.

Beschreibung: We report the design, construction, and performances of a microwave (MW) heating device for laboratory experiments with non-contact, homogeneous internal heating. The device generates MW radiation at 2.47 GHz from a commercial magnetron supplied by a pulsed current inverter using proprietary, feedback based command and control hardware and software. Specially designed MW launchers direct the MW radiation into the sample through a MW homogenizer, devised to even the MW power distribution into the sample's volume. An adjustable MW circuit adapts the MW generator to the load (i.e., the sample) placed in the experiment chamber. Dedicated heatsinks maintain the MW circuits at constant temperature throughout the experiment. Openings for laser scanning for image acquisition with a CCD camera and for the cooling circuits are protected by special MW filters. The performances of the device are analyzed in terms of heating uniformity, long term output power stability, and load matching. The device is used for small scale experiments simulating Earth's mantle convection. The 30 × 30 × 5 cm 3 convection tank is filled with a water‑based viscous fluid. A uniform and constant temperature is maintained at the upper boundary by an aluminum heat exchanger and adiabatic conditions apply at the tank base. We characterize the geometry of the convective regime as well as its bulk thermal evolution by measuring the velocity field by Particle Image Velocimetry and the temperature field by using Thermochromic Liquid Crystals.

Beschreibung: This paper announces the implementation of a long wavelength infrared camera to obtain high-speed thermal images of an aircraft engine's in-service thermal barrier coated turbine blades. Long wavelength thermal images were captured of first-stage blades. The achieved temporal and spatial resolutions allowed for the identification of cooling-hole locations. The software and synchronization components of the system allowed for the selection of any blade on the turbine wheel, with tuning capability to image from leading edge to trailing edge. Its first application delivered calibrated thermal images as a function of turbine rotational speed at both steady state conditions and during engine transients. In advance of presenting these data for the purpose of understanding engine operation, this paper focuses on the components of the system, verification of high-speed synchronized operation, and the integration of the system with the commercial jet engine test bed.

Beschreibung: We present a home built electrochemical scanning tunneling microscope (ECSTM) with very high stability and repeatability. Its coarse approach is driven by a closely stacked piezo motor of GeckoDrive type with four rigid clamping points, which enhances the rigidity, compactness, and stability greatly. It can give high clarity atomic resolution images without sound and vibration isolations. Its drifting rates in XY and Z directions in solution are as low as 84 pm/min and 59 pm/min, respectively. In addition, repeatable coarse approaches in solution within 2 mm travel distance show a lateral deviation less than 50 nm. The gas environment can be well controlled to lower the evaporation rate of the cell, thus reducing the contamination and elongating the measurement time. Atomically resolved SO 4 2− image on Au (111) work electrode is demonstrated to show the performance of the ECSTM.