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  • 1
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    Digitized detection of gamma-ray signals concentrated in narrow time windows for transient positron annihilation lifetime spectroscopy (2014)
    American Institute of Physics (AIP)
    Details
    Publication Date: 2014-12-16
    Description: 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.
    Print ISSN: 0034-6748
    Electronic ISSN: 1089-7623
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Published by American Institute of Physics (AIP)
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  • 2
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    Tracking mechanical and morphological dynamics of regenerating Hydra tissue fragments using a two fingered micro-robotic hand (2016)
    American Institute of Physics (AIP)
    Details
    Publication Date: 2016-03-12
    Description: Regeneration of a tissue fragment of freshwater polyp Hydra is accompanied by significant morphological fluctuations, suggesting the generation of active forces. In this study, we utilized a two fingered micro-robotic hand to gain insights into the mechanics of regenerating tissues. Taking advantage of a high force sensitivity (∼1 nN) of our micro-hand, we non-invasively acquired the bulk elastic modulus of tissues by keeping the strain levels low ( ε  
    Print ISSN: 0003-6951
    Electronic ISSN: 1077-3118
    Topics: Physics
    Published by American Institute of Physics (AIP)
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  • 3
    Electronic Resource
    Electronic Resource
    Magneto-optic disks for high-density recording with a shorter wavelength laser (abstract) : 35th annual conference on magnetism and magnetic materials (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 69 (1991), S. 4773-4773 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: In order to increase the recording density of the optic disks, it is necessary to shorten the wavelength of the laser beams. Recently, Pt/Co multilayered films have been investigated for the optic recording media using the laser with the wavelength shorter than 600 nm because of the high Kerr rotation. It is, however, difficult to write the magnetic domains with the diameter less than 0.5 μm stably due to the small coercivity and the uniaxial anisotropy field. On the other hand, it is easy to write the domains with the diameter of 0.3 μm on the conventional media of TbFeCo. To use this advantage, the exchange-coupled double-layered film of (Pt/Co)/(TbFeCo) has been developed. The disk structure is Al-alloy/nitride/(Pt/Co)/TbFeCo/nitride/substrate. The multilayered film of Pt/Co has been optimized to write smaller domains and have a higher Kerr rotation for high output signal. Consequently, the thickness is 20 A(ring)/5 A(ring), respectively. It has been confirmed that the 0.3 μm φ domains can be written clearly and the figure of merit (square root of)Rθk is twice as large as that of the conventional TbFeCo at the short wavelength region of 400–500 nm. Finally, the read/write characteristics have been tested with the SHG laser of 532 nm.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.348275
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  • 4
    Electronic Resource
    Electronic Resource
    Bloch line propagation with film thickness modulation bit patterns (abstract) : 35th annual conference on magnetism and magnetic materials (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 69 (1991), S. 5767-5767 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Bloch line (BL) propagation with a field-access scheme is necessary for the memory with low power consumption and high storage density. Previously we reported the field-access propagation using Co-Pt bit patterns.1 In these propagation patterns, (a) the drive field margins depend on the BL propagating direction to the magnetized direction of Co-Pt patterns and (b) the operating bias field margins are different at each corner of the stripe domain. The purpose of this paper is to solve these two problems. A new propagation method has been investigated using film thickness modulation patterns.2 The materials used here were magnetic bubble garnet films with composition of (YSmLuCa)3(FeGe)5O12. Fundamental characteristics of the samples are as follows: saturation induction 4πMs 200 G, anisotropy field Hk 1700 Oe, stripe width w and thickness h 5 μm. The thickness modulation patterns with an amplitude of about 1000 A were fabricated with the ion milling method. The stripe domains were stabilized around the 100% etched grooves, and aligned with 18 μm period. BL pair was propagated in the all part of the stripe domain walls at 500 kHz frequency, applying the triangular bias pulsed field with 50 ns rise time and 1000 ns fall time. As the result of the experiments, it has been found that the drive field margins are independent of BL propagation direction and the difference in the operating bias field margins at the each corner of the stripe domain becomes smaller. The BL propagation around the stripe domain was achieved with 5% bias field margin at the drive field of 8.5 Oe.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.347869
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  • 5
    Electronic Resource
    Electronic Resource
    Positron annihilation in a metal-oxide semiconductor studied by using a pulsed monoenergetic positron beam (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 74 (1993), S. 7251-7256 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The positron annihilation in a metal-oxide semiconductor was studied by using a pulsed monoenergetic positron beam. Lifetime spectra of positrons were measured as a function of incident positron energy for a polycrystalline Si(100 nm)/SiO2(400 nm)/Si specimen. Applying a gate voltage between the polycrystalline Si film and the Si substrate, positrons implanted into the specimen were accumulated at the SiO2/Si interface. From the measurements, it was found that the annihilation probability of ortho-positronium (ortho-Ps) drastically decreased at the SiO2/Si interface. The observed inhibition of the Ps formation was attributed to an interaction between positrons and defects at the SiO2/Si interface.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.355015
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  • 6
    Electronic Resource
    Electronic Resource
    Nanostructure of thin amorphous hydrogenated carbon films studied by positron annihilation and photoluminescence (2001)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 90 (2001), S. 404-410 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We deposited polymer-like a-C:H films using the plasma-enhanced chemical vapor deposition technique and characterized film microstructure by variable-energy positron lifetime spectroscopy, photoluminescence (PL), and UV-visible absorption spectroscopy. It was confirmed that PL occurs from a chromophore in a sp2 cluster as a result of fast recombination of a photoexcited electron-hole pair. Positron annihilation lifetime spectroscopy showed that positronium (Ps) formation takes place via electron-positron recombination in the sp3 matrix. The lifetime of ortho-positronium (o-Ps) in our a-C:H films was similar to that in polyethylene, indicating their polymer-like nature. The relative PL efficiency increased by about an order of magnitude with increasing film band gap from 1.3 to 3.4 eV, which can be related to the decreasing concentration of nonradiative centers. On the other hand, Ps formation was much less influenced by the band gap and nonradiative centers. Comparison of this result with that for polyethylene mixed with carbon-black nanoparticles, where a considerable reduction in Ps formation was observed, showed that nonradiative centers were of a different nature from the defects on the carbon nanoparticle surface. This work demonstrated the usefulness of positron lifetime spectroscopy combined with optical measurements to study the nanostructure of a-C:H. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1378063
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  • 7
    Electronic Resource
    Electronic Resource
    Design and manufacture of a 10-T superconducting wiggler magnet at TERAS : Proceedings of the 5th international conference on synchrotron radiation instrumentation (1995)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 66 (1995), S. 1960-1963 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: The 10-T wiggler is an iron-cored superconducting wiggler destined for Electrotechnical Laboratory's 800-MeV electron storage ring to enhance the available radiation. The design and manufacturing contract for this magnet was started in April 1990 and was preceded by a feasibility study. The major features of the magnet are described in the article. Also, the effect of the superconducting wiggler with high magnetic field on the stored electron beam has been simulated. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1145770
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  • 8
    Electronic Resource
    Electronic Resource
    Single bunch injection system of the storage ring NIJI-IV for free electron laser use (1995)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 66 (1995), S. 2796-2800 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: The system of single bunch injection (SBI) for the storage ring NIJI-IV was completed. The system was used for the injection of the short pulse beams from an electron gun into only one of the 16 rf buckets in the ring. On a compact storage ring, the multipulse beams in one pulse train can be stored into only one of many bunches by one injection. The optimum number of the grid pulse in one pulse train was determined to improve the storage efficiency and the storage current by one injection. The keeping time of the bump orbit was calculated by using the transfer matrices. The optimum pulse number obtained by the calculation is 2. In the SBI system, the number of grid pulses in one pulse train can be selected by the gate circuit. A snap off diode and a clip line are used to generate 2 ns grid pulses. The measured grid pulse was shorter than the longitudinal space 5.5 ns of the rf bucket with voltage of −80 V. The EIMAC Y-646B cathode-grid assembly is used as the electron source. It is expected that the injection system provides a higher peak current and easier free electron laser use operation in comparison with the rf-knockout system. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1145557
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  • 9
    Electronic Resource
    Electronic Resource
    Positronium formation in SiO2 films grown on Si substrates studied by monoenergetic positron beams (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 75 (1994), S. 3822-3828 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The annihilation characteristics of positrons in SiO2 films grown on Si substrates were studied by using monoenergetic positron beams. Doppler broadening profiles of the annihilation radiation and lifetime spectra of positrons were measured as a function of incident positron energy for SiO2 (166 nm)/Si specimens fabricated by thermal oxidation. From the measurements, it was found that about 90% of positrons implanted into the SiO2 film annihilate from positronium (Ps) states. This fact was due to the trapping of positrons by open-space defects and a resultant enhanced formation of Ps in such regions. For the SiO2 film grown at 650 °C, the lifetime of ortho-Ps was found to be shorter than that in the film grown at 1000 °C. This result suggests that the volume of open-space defects in the SiO2 film decreased with decreasing the growth rate of the SiO2 film.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.356059
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  • 10
    Electronic Resource
    Electronic Resource
    Nanoporous structure of sputter-deposited silicon oxide films characterized by positronium annihilation spectroscopy (2002)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 91 (2002), S. 1704-1706 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Positronium annihilation was applied to characterize the nanoporous structure of thin silicon oxide films sputter-deposited at different argon pressures ranging from 0.1 to 2.0 Pa. At higher argon pressures, the 3γ decay probability of ortho-positronium (o-Ps) was substantially enhanced. A comparison of this result with that obtained for capped samples indicated that: (a) 3γ annihilation is due to the intrinsic decay of o-Ps diffusing out from the film into vacuum and (b) films deposited at high argon pressures contain highly connected, open pores. Positron lifetime spectroscopy measurements on the capped films showed that the characteristic size of the pores can be as large as 2.6 nm, depending on the argon pressure. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1428787
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