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  • 1
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The effect of thermal-diffusion charge on the x-ray energy response of silicon surface-barrier (SSB) detectors have generally been ignored; consequently, the SSB response has been believed to be analyzed using the thickness of the depletion layer alone. Our new theory on the SSB x-ray response [J. Appl. Phys. 72, 3363 (1992)] was prepared for addressing recent confusion on plasma x-ray analyses using SSB detectors [Rev. Sci. Instrum. 59, 1380 (1988); 61, 693 (1990); 63, 4850 (1992)]. This approach was made under the assumption of a dominant contribution of the diffusion-charge signal in the vicinity of the x-ray incident location because of the strong reduction of the x-ray produced charge within the thermal-diffusion length. In this report, the comparison between this approximation (having an approximated solution) and the exact numerical calculation (using an integral form) is carried out. Necessity and importance of such three-dimensional treatments for the data analyses as well as the design of multichannel semiconductor-array detectors developed for plasma x-ray tomography diagnostics are highlighted. Furthermore, for the total diffusing-charge amount, the calculated results from our theory and the values using the comment from Donolato agree well within the accuracy of 1%.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: An analytical method based on a new theoretical model for the x-ray energy responses of silicon surface-barrier (SSB) detectors has been proposed. This method may address a recent confusing issue in the x-ray detection characteristics of SSB semiconductor detectors; that is, the x-ray responses of SSB detectors as well as p-i-n diodes used in underbiased operations were recently found to be contrary to the commonly held belief that the x-ray sensitivity of an SSB detector is determined by the thickness of the depletion layer. The model presented includes a signal contribution from thermally diffusing charge that is created in the field-free substrate region within a diffusion length from the depletion layer along with a signal contribution from charge created in the depletion layer. This model predicts a large signal contribution from the charge-diffusion effect on the SSB responses to high-energy x rays. Formulas and calculated results supporting SSB calibration data have been represented. These analytical methods might be developed to apply the analyses and predictions of energy responses of various types of silicon detectors including p-i-n diodes as well as charge-coupled devices.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 61 (1990), S. 1247-1250 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: The Fraunhofer diffraction measurements from a tandem mirror plasma are reported. The successful use of a new multichannel detector array permits a detailed study of k−ω spectra of long-wavelength waves with a few plasma shots. The observed dispersion relations are in good agreement with those of drift wave including a Doppler shift due to E×B rotation velocity.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 62 (1991), S. 899-905 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Features of the electrostatic energy analyzer of a cylindrical type are described with the aim of measuring the end-loss ions in the tandem mirror GAMMA 10. The analyzer provides us with information about ion density distributions in a loss-cone region of velocity space as well as plug potential in the tandem mirror. Application of the analyzer to the tandem mirror experiments and the energy spectrum analysis are discussed.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Semiconductor ion detectors are developed and characterized for the purpose of the use for high-output and wide-energy-sensitive upgraded ion diagnostics. In particular, the theoretical basis for the simulation of the semiconductor ion-energy response along with its experimental verification using monoenergetic ion beams is investigated. High-output-current semiconductor signals ranging from one to three orders of magnitude larger than those from widely employed commercially available silicon-surface-barrier detectors are attained in the ion-energy region above 0.2 keV. These data are found to be well fitted by the developed simulation results. In order to observe ion signals alone under the complicated condition of the simultaneous incidence of ions, electrons, and x rays, we develop an upgraded electrostatic ion-energy spectrometer, having specific structures with obliquely positioned multiple grids. The combination of the installation of such a low-ion-energy-sensitive semiconductor detector and this novel-structured ion spectrometer provides a new electrostatic large-output and low-energy-sensitive ion spectrometer having no signal disturbances from the other plasma species and giving no perturbations to ambient plasma-confining magnetic fields. Accordingly, this novel compact-sized electrostatic ion spectrometer using a single-channel semiconductor collector provides temporal-evolution data on ion-energy spectra during a single plasma shot alone; therefore, this spectrometer is usefully applicable to the opportunities of the observations of ion parameters in both divertor and hot-core regions. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: For the purpose of plasma-ion-energy analyses in a wide-energy range from a few hundred eV to hundreds of keV, upgraded semiconductor detectors are newly fabricated and characterized using a test-ion-beam line from 0.3 to 12 keV. In particular, the detectable lowest-ion energy is drastically improved at least down to 0.3 keV; this energy is one to two orders-of-magnitude better than those for commercially available Si-surface-barrier diodes employed for previous plasma-ion diagnostics. A signal-to-noise ratio of two to three orders-of-magnitude better than that for usual metal-collector detectors is demonstrated for the compact-sized semiconductor along with the availability of the use under conditions of a good vacuum and a strong-magnetic field. Such characteristics are achieved due to the improving methods of the optimization of the thicknesses of a Si dead layer and a SiO2 layer, as well as the nitrogen-doping technique near the depletion layer along with minimizing impurity concentrations in Si. Such an upgraded capability of an extremely low-energy-ion detection with the low-noise characteristics enlarges research regimes of plasma-ion behavior using semiconductor detectors not only in the divertor regions of tokamaks but in wider spectra of open-field plasma devices including tandem mirrors. An application of the semiconductor ion detector for plasma-ion diagnostics is demonstrated in a specially designed ion-spectrometer structure. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 65 (1994), S. 936-942 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A new type of end-loss-ion energy analyzer (ELA; a multigridded Faraday cup) is applied to measure plasma ion temperatures Tip and plasma potentials ΦP in the GAMMA 10 tandem-mirror device. As compared with conventional-type ELA, this new ELA has obliquely placed ion- and secondary-electron-repeller grids and a collector plate with respect to external tandem-mirror magnetic fields. One of the most useful capabilities of this new ELA for precise ion measurements is to greatly reduce the current of high-energy electrons onto the collector plate. Also, this compact-sized ELA is scannable in the plasma to obtain radial profiles of Tip and ΦP without providing any perturbations of the tandem-mirror magnetic fields because it neither adds its own magnetic field nor needs to shield against the ambient magnetic field. Ion trajectories in the new ELA are numerically calculated so as to make a further understanding of its physics principles and to optimize its design. The energy-calibration experiments for the new ELA are carried out using ion beams; a fairly good agreement in the analyzed beam energies from the new ELA data and from conventional-type ELA data is attained. Furthermore, the first application of the new ELA to plasma diagnostics is made; a substantial reduction in energetic-electron influxes onto real ion signals makes a significant improvement in the analyses of Tip and ΦP.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 63 (1992), S. 3167-3173 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A new method is developed for mode analysis of microwaves propagating in an oversize waveguide. A curved reflector is used to disperse the different modes in different directions. The locations of the mode powers are systematically distributed on an intercepting absorber plane. An infrared camera is used for quick visual analysis of the mode map produced as a temperature distribution on the absorber sheet. Detailed analysis is also made by numerically processing the image data. Polarizations of the constituent modes can be determined with a rotated microwave receiver. Usefulness of this method is experimentally demonstrated by comparison with other techniques.
    Type of Medium: Electronic Resource
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  • 9
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: The first results of simultaneous observations of temporally and spatially resolved electron temperatures (Te) in both circularly shaped central-cell and elliptically shaped anchor regions are reported in the GAMMA 10 tandem mirror. A data set is provided using a novel matrix-type x-ray semiconductor detector. The detector has seven "matrix columns" for the measurement of plasma x-ray profiles along with six "matrix rows" for simultaneous analyses of six different x-ray-energy ranges by the fabrication of six different thicknesses of SiO2 semiconductor surface layers from 1 to 495 nm as ultrathin and unbreakable "x-ray absorption filters." Such a matrix idea enables us to analyze x-ray tomography data in the Te region down to a few tens of eV. Simultaneous application of the x-ray detectors in the central-cell and the anchor region gives information on not only detailed electron behavior in each region but also the mutually communicating relation between the two regions: The role of the anchor-region plasmas in magnetohydrodynamic plasma stabilization in the central-cell plasmas is confirmed by the data from these detailed simultaneous electron observations. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 10
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: For the purpose of the developments of wide-energy-range-sensitive x-ray detectors, we have designed and fabricated a new-type multilayer semiconductor x-ray detector. This new-type detector has been characterized using synchrotron radiation from a 2.5-GeV positron storage ring at the Photon Factory of the National Laboratory for High Energy Physics (KEK). This new detector is essentially composed of four layers of commercially available photodiodes. Each photodiode is made from a 300-μm thick, and a 10×10-mm square-shaped wafer. For the common affiliation of these individual photodiodes, the quantum efficiency normalized by the photon energy η/E begins to decrease at 8 keV, and then η/E decreases down to 26% at 20 keV. On the other hand, for our newly designed detector a flat response even in the 10–20-keV energy regime (beam line 15C at the Photon Factory) is observed, and even at 100 keV η/E〈30% is still anticipated. This new x-ray detector has various advantages: (i) A compact, and (ii) outgas-free detector for a high-vacuum use, along with (iii) a high degree of immunity to ambient magnetic fields. Furthermore, (iv) the combination of the x-ray signal outputs from each detector layer provides information on the x-ray emitting electron energies. These properties are quite suitable for the use of the fusion-oriented plasma x-ray diagnostics under intense-magnetic field and high-vacuum conditions so as to interpret wide-band x-ray emitting electron-velocity distribution functions from the x-ray data. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
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