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  • 1
    Digitale Medien
    Digitale Medien
    Reply to "Comment on ‘A theory on the x-ray sensitivity of a silicon surface-barrier detector including a thermal charge-diffusion effect' '' [J. Appl. Phys. 72, 3363 (1992)] (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 74 (1993), S. 1463-1464 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: 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%.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.354864
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  • 2
    Digitale Medien
    Digitale Medien
    A theory on the x-ray sensitivity of a silicon surface-barrier detector including a thermal charge-diffusion effect (1992)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 72 (1992), S. 3363-3373 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: 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.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.351458
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  • 3
    Digitale Medien
    Digitale Medien
    High performance and current drive experiments in the JAERI Tokamak-60 Upgradef| (1994)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 1 (1994), S. 1489-1496 
    Details
    ISSN: 1089-7674
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Recent high-fusion-triple-product and current drive experiments in the JAERI Tokamak-60 Upgrade (JT-60U) [Plasma Devices Oper. 1, 43 (1990)] are reported. The fusion triple product of 1.1×1021 m−3 s keV has been achieved in a more improved confinement mode (high-βp H-mode) in which the confinement is improved in the edge region as well as the core region. The most remarkable feature in the improved confinement mode is the multistage formation of transport barriers. The transport barrier was formed in the plasma interior first. After that, the transport barrier was formed in the edge region. For steady-state operation and current profile control, lower hybrid current drive (LHCD) and neutral beam current drive (NBCD) experiments with bootstrap current contribution are also in progress. Full current drive of 3.6 MA has been achieved at a density of 1.1×1019 m−3 with a current drive efficiency of ne⋅Rp⋅ICD/PLH=2.5×1019 m−2 A W−1 with a 5.7 MW LH wave injection. Current profile control with various LH wave spectra and with NBCD were also demonstrated.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.870943
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  • 4
    Digitale Medien
    Digitale Medien
    Absolute calibration of the JT-60U neutron monitor using a 252Cf neutron source (abstract)a) : Proceedings of the 9th topical conference on high temperature plasma diagnostics (1992)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 63 (1992), S. 4558-4558 
    Details
    ISSN: 1089-7623
    Quelle: AIP Digital Archive
    Thema: Physik , Elektrotechnik, Elektronik, Nachrichtentechnik
    Notizen: Absolutely calibrated measurements of the neutron yield are important for the evaluation of the plasma performance such as the fusion gain Q in D-D operating tokamaks. The time-resolved neutron yield is measured with 235U and 238U fission chambers and 3He proportional counters in the JT-60U tokamak. The in situ calibration was performed by moving the 252Cf neutron source toroidally through the JT-60 vacuum vessel. Detection efficiencies of three 235U and two 3He detectors were measured for 92 locations of the neutron point source in toroidal scans at two different major radii. The total detection efficiency for the torus neutron source was obtained by the averaging the point efficiencies over the whole toroidal angle. The uncertainty of the resulting detection efficiency for the plasma neutrons is estimated to be ±11%.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.1143666
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  • 5
    Digitale Medien
    Digitale Medien
    Pellet ablation profile measurements on the JT-60 tokamak : Eighth topical conference on high−temperature plasma diagnostics (1990)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 61 (1990), S. 3090-3092 
    Details
    ISSN: 1089-7623
    Quelle: AIP Digital Archive
    Thema: Physik , Elektrotechnik, Elektronik, Nachrichtentechnik
    Notizen: Four hydrogen pellets, two of 3 mm(large-closed-square)×3 mml pellets and two of 4 mmF(Slashthrough accent mark)×4 mml pellets, with the velocity of ∼2.3 km/s, were injected to OH and NB heated plasmas by a four-barrel pneumatic injector on the JT-60 tokamak. The pellet ablation profile was estimated by the measurement of the Hα emissions originating from the ablation cloud using a fiber optics array combined with the Hα -filtered multichannel photodiode. The fiber optics array consisting of ten channel bundles views the pellet pass in the vacuum vessel. The optical fiber was developed to tolerate baking up to 300 °C. The measured ablation profiles were compared with the calculated one by the neutral gas shielding model with a self-limiting effect. A good agreement was obtained between measured and calculated ablation profiles in OH plasmas; however, the fast-ion-induced ablation needed to be taken into account in the calculation for NB-heated plasmas.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.1141690
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  • 6
    Digitale Medien
    Digitale Medien
    Absolute calibration of the JT-60U neutron monitors using a 252Cf neutron sourcea) (1992)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 63 (1992), S. 5270-5278 
    Details
    ISSN: 1089-7623
    Quelle: AIP Digital Archive
    Thema: Physik , Elektrotechnik, Elektronik, Nachrichtentechnik
    Notizen: Absolutely calibrated measurements of the neutron yield are important for the evaluation of plasma performance such as the fusion gain Q in D–D operating tokamaks. The time-resolved neutron yield is measured with 235U and 238U fission chambers and 3He proportional counters in the JT-60U tokamak. The in situ calibration was performed by moving the 252Cf neutron source toroidally through the JT-60 vacuum vessel. Detection efficiencies of three 235U and two 3He detectors were measured for 92 locations of the neutron point source in toroidal scans at two different major radii. The total detection efficiency for the torus neutron source was obtained by averaging the point efficiencies over the whole toroidal angle. The uncertainty of the resulting detection efficiency for the plasma neutrons is estimated to be ±11%.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.1143439
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  • 7
    Digitale Medien
    Digitale Medien
    A filter bank system for scattered spectrum analysis in collective Thomson scattering diagnostic on JT-60 (2000)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 71 (2000), S. 4445-4448 
    Details
    ISSN: 1089-7623
    Quelle: AIP Digital Archive
    Thema: Physik , Elektrotechnik, Elektronik, Nachrichtentechnik
    Notizen: In JT-60, a collective Thomson scattering (CTS) diagnostic system based on a pulsed CO2 laser (wavelength 10.6 μm, beam energy 15 J, pulse width 1 μs) has been developed to measure ion temperature and velocity distribution of fast ions to demonstrate the feasibility of measurements of confined alpha particles. A high power pulsed CO2 laser and heterodyne receiver system using a quantum-well infrared photodetector (QWIP) has been developed and installed in the diagnostic room. In order to resolve frequency distribution of pulsed scattered light (1 μs), we developed a wideband filter bank system (0.4–4.5 GHz) for scattered spectrum analysis in JT-60 CTS diagnostic. The detector bandwidth and frequency resolution are both determined by the calculation results of expected scattered spectrum. In order to realize wideband multichannel detection, cascade connected seventh order simultaneous-Chebyshev (elliptic) bandpass filters were adopted. Signal to noise ratio based on the noise equivalent power of the QWIP receiver and laser pulse length are also evaluated. © 2000 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.1326932
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  • 8
    Digitale Medien
    Digitale Medien
    Advanced impurity measurement for deuterium–tritium-burning plasmas using pulsed CO2 laser collective Thomson scattering (2000)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 71 (2000), S. 3718-3722 
    Details
    ISSN: 1089-7623
    Quelle: AIP Digital Archive
    Thema: Physik , Elektrotechnik, Elektronik, Nachrichtentechnik
    Notizen: Knowledge of the dynamics and concentration of impurities in the plasma core is crucial to the development of a deuterium–tritium (DT) tokamak fusion reactor. In this article, we first describe an advanced diagnostic technique to measure the impurities, thermalized helium density, and the deuterium-to-tritium density ratio in DT-burning plasmas. The measurement is made by small-angle collective Thomson scattering using a high-power pulsed CO2 laser and heterodyne receiver system. The component of scattered laser power nearly perpendicular to the magnetic field gives rise to ion cyclotron modulation of the scattered spectrum. Scattered spectrum of expected impurities (Ar, Be, and He ash) are presented for the International Thermonuclear Experimental Reactor plasmas. The method for the determination of the helium ash density and deuterium-to-tritium ratio are also proposed. Modulation spectra as a function of frequency for different magnetic-field angles are confirmed. Experimental requirements to measure a scattered spectrum with fine details resulting from ion cyclotron oscillations are also discussed. © 2000 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.1311940
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  • 9
    Digitale Medien
    Digitale Medien
    A newly developed multilayer semiconductor x-ray detector for the observations of wide energy-range x rays : 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. 2311-2313 
    Details
    ISSN: 1089-7623
    Quelle: AIP Digital Archive
    Thema: Physik , Elektrotechnik, Elektronik, Nachrichtentechnik
    Notizen: 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.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.1145673
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  • 10
    Digitale Medien
    Digitale Medien
    Experimental verification of the three-dimensional diffusion effect of x-ray-produced charges in semiconductor x-ray detectors on the quantum-efficiency enhancement : 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. 2300-2302 
    Details
    ISSN: 1089-7623
    Quelle: AIP Digital Archive
    Thema: Physik , Elektrotechnik, Elektronik, Nachrichtentechnik
    Notizen: One of the characteristic physical principles of our recently proposed theory on the x-ray-energy response of a semiconductor x-ray detector is the effect of the three-dimensional diffusion of x-ray-produced charges in a semiconductor field-free substrate region. It is found and reported that the quantum efficiency of a semiconductor x-ray detector is enhanced when this phenomenon is taken into account, and the data on the x-ray-energy response of the semiconductor detector using monochromatized synchrotron radiation at the Photon Factory are actually well fitted by the theory. In addition, we measure the diffusion length L of the detector using a precisely collimated x-ray narrow beam and a multichannel detector array setting on a μm-order position-controllable stage. The verification of the consistency between this observed value of L and the predicted value of L from our theory on the quantum efficiency, has been achieved. © 1995 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.1145669
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