T Iguchi

Publications (44)22.66 Total impact

• Article: Development of neutron spectrometer toward deuterium plasma diagnostics in LHD.

  H Tomita, H Iwai, T Iguchi, M Isobe, J Kawarabayashi, C Konno
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  ABSTRACT: Neutron spectrometer based on coincident counting of associated particles has been developed for deuterium plasma diagnostics on Large Helical Device (LHD) at the National Institute for Fusion Science. Efficient detection of 2.5 MeV neutron with high energy resolution would be achievable by coincident detection of a scattered neutron and a recoiled proton associated with an elastic scattering of incident neutron in a plastic scintillator as a radiator. The calculated neutron spectra from deuterium plasma heated by neutral beam injection indicate that the energy resolution of better than 7% is required for the spectrometer to evaluate energetic deuterium confinement. By using a prototype of the proposed spectrometer, the energy resolution of 6.3% and the detection efficiency of 3.3×10(-7) count/neutron were experimentally demonstrated for 2.5 MeV monoenergetic neutron, respectively.
  The Review of scientific instruments 10/2010; 81(10):10D309. · 1.52 Impact Factor
• Source

  Available from: nifs.ac.jp

  Article: Fusion product diagnostics planned for Large Helical Device deuterium experiment.

  M Isobe, H Yamanishi, M Osakabe, H Miyake, H Tomita, K Watanabe, H Iwai, Y Nomura, N Nishio, K Ishii, J H Kaneko, J Kawarabayashi, E Takada, A Uritani, M Sasao, T Iguchi, Y Takeiri, H Yamada
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  ABSTRACT: Deuterium experiment on the Large Helical Device (LHD) is now being planned at the National Institute for Fusion Science. The fusion product diagnostics systems currently considered for installation on LHD are described in this paper. The systems will include a time-resolved neutron yield monitor based on neutron gas counters, a time-integrated neutron yield monitor based on activation techniques, a multicollimator scintillation detector array for diagnosing spatial distribution of neutron emission rate, 2.5 MeV neutron spectrometer, 14 MeV neutron counter, and prompt γ-ray diagnostics.
  The Review of scientific instruments 10/2010; 81(10):10D310. · 1.52 Impact Factor
• Source

  Available from: ac.jp

  Conference Proceeding: Development of 2.5MeV neutron spectrometer for helical deuterium plasma experiment

  H. Iwai, T. Iguchi, H. Tomita, J. Kawarabayashi, M. Isobe, C. Konno
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  ABSTRACT: A neutron spectrometer with associated particles coincident time-of-flight technique is being developed for deuterium plasma experiments in a large helical fusion device. In this experiment, the energy resolution less than 7% and the detection efficiency larger than 10^-6 counts/neutron is required for the plasma diagnostics based on neutron spectrometry. The prototype spectrometer was partly assembled and the detector performance was experimentally checked at Fusion Neutron Source of Japan Atomic Energy Agency. By selecting the events with low energy loss from all coincident events in the radiator, the experimental results showed that the neutron spectrometer could achieve an energy resolution around 6.7% under a detection efficiency of 3.3×10^-7 counts/neutron for DD neutrons. To improve the detection efficiency, the configuration of the neutron spectrometer system was designed toward the DD plasma experiment at an existent large helical fusion device.
  Nuclear Science Symposium Conference Record (NSS/MIC), 2009 IEEE; 12/2009
• Conference Proceeding: Development of Compact Wide-Angle Imaging Detector for MeV Gamma-Rays using Stacked BGO Scintillator Rods

  K. Watanabe, S. Mihoya, J. Kawarabayashi, T. Iguchi
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  ABSTRACT: We are developing a compact wide-angle imaging detector for MeV gamma-rays using stacked BGO scintillator rods to apply to neutron induced prompt gamma-ray analysis (NPGA), which is one of the promising methods for non-destructive detection of hidden explosives by measuring characteristic gamma-rays produced from chemical elements. The gamma-ray imaging in NPGA applications is also necessary to locate them and improve the signal-to-noise ratio. A compact wide-angle imaging detector has an advantage in detection efficiency, because it can take images at short distance from inspection objects. For a compact wide-angle imaging detector for MeV gamma-rays, we have proposed the image reconstruction technique based on the statistical estimation algorithm using stacked BGO scintillator rods that can get information on energies and 3D positions. In this paper, we mainly discussed an information processing method for recorded signals especially to provide the additional function rejecting pile-up events, which makes our detector possible to operate in high dose filed. Through the EGS4 simulations modeling our detector units, we successfully demonstrated that the pile-up events can be suppressed by picking out only events with small spatial deviation of scintillation positions. In addition, we experimentally demonstrated nitrogen imaging based on NPGA using our gamma-ray detector.
  Nuclear Science Symposium Conference Record, 2006. IEEE; 12/2006
• Source

  Available from: nagoya-u.ac.jp

  Article: Novel concept of time-of-flight neutron spectrometer for measurement of the D/T burning ratio in the ITER

  K. Asai, N. Naoi, T. Iguchi, K. Watanabe, J. Kawarabayashi, T. Nishitani
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  ABSTRACT: A time-of-flight (TOF) neutron spectrometer is a candidate for the measurement of the D/T burning ratio in the International Thermonuclear Experimental Reactor (ITER). In ITER high-power experiments, the TOF system suffers from a high event rate or accidental counts due to high radiation intensities, which is one of several background sources in DD neutron measurement. We herein propose a new neutron spectrometer to apply to the measurement of the D/T burning ratio in the ITER high-power operation region. This system is based on the conventional double-crystal TOF method and consists of a water cell and several pairs of scintillators. A water cell is inserted before the first scintillator of the TOF system and acts as a radiator or neutron scattering material. Because DD neutrons have a larger cross section of elastic scattering with hydrogen than DT neutrons, the elastic scattering in the radiator enhances the relative ratio of DD/DT intensity by approximately three times before entering the TOF system. The enhancement of the relative intensity of DD neutrons makes the detection of DD neutrons easier. The feasibility of this method as a neutron spectrometer has been verified through a preliminary experiment using a DT neutron beam ( 20 mm Φ ) at the Fusion Neutronics Source, Japan Atomic Energy Agency. The present article describes the basic performance of the prototype system.
  Review of Scientific Instruments 11/2006; · 1.37 Impact Factor
• Conference Proceeding: Development of compact Compton gamma camera for non-destructive detection and location of hidden explosives with neutron induced prompt gamma-ray imaging

  T. Iguchi, J. Kawarabayashi, K. Watanabe, H. Kenjyo, A. Uritani
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  ABSTRACT: As a unique gamma-ray sensor for detection and location of hidden explosives with neutron induced prompt gamma-ray analysis, we are developing a compact and efficient Compton gamma camera based on stacked BGO scintillator rods to deduce the incident direction of characteristic 10.8 MeV gamma-rays produced from nitrogen abundant in explosives through neutron capture reaction. The detector unit consists of 5.4 mm times; 5.4 mm times 150 mm BGO scintillator rods stacked into an 8times8 array and two multi-anode photomultiplier tubes mounted at the both ends, which can measure three-dimensional position and intensity of scintillations produced through Compton multiple scattering inside the detector and follow the track of scattered gamma-rays backward according to Compton scattering kinematics to estimate the location of a specific energy gamma-ray source without any mechanical collimation. We have designed and constructed the prototype system of 6 detector units with multi-functional ASIC for multichannel signal read-out. The outline and applicability of this system is presented with some preliminary performance tests by using quasi-monochromatic 10.8 MeV gamma-ray beams produced through laser-Compton scattering with the electron storage ring
  Nuclear Science Symposium Conference Record, 2005 IEEE; 11/2005
• Article: Novel dose rate monitoring for intense radiation fields based on cavity ring-down laser spectroscopy

  H. Tomita, K. Watanabe, J. Kawarabayashi, T. Iguchi
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  ABSTRACT: To monitor dose rates in intense radiation fields, we are developing a novel dose rate monitoring method based on cavity ring-down laser absorption spectroscopy, where the dose rate of the radiation field can be derived from concentrations of the radiation induced chemical species in irradiated gas. We have attempted to verify the operational principle of this method through off-line/on-line measurements of ⁶⁰Co gamma-ray induced O₃ and NO₂ in air. The results of these experiments demonstrated that the present method is quite useful for dose rate monitoring in intense radiation fields with high radiation resistance, by showing the detectable range of an absorbed dose rate from 0.5 to 2000 Gy/s with a time resolution of about 30 s.
  IEEE Transactions on Nuclear Science 11/2005; · 1.45 Impact Factor
• Conference Proceeding: Novel dose rate monitoring for intense radiation fields based on cavity ring-down laser spectroscopy

  H Tomita, K Watanabe, J. Kawarabayashi, T Iguchi, N. Nariyama
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  ABSTRACT: For dose rate monitoring in high level radiation fields, we have proposed a concept of novel dose rate monitoring method based on high sensitive laser absorption spectroscopy technique for radiation induced chemical species. The yield of the species depends on the intensity of the radiation field. The dose rate of the radiation field, therefore, can be derived from concentrations of the species. We have adopted cavity ring-down spectroscopy, which is an ultra high sensitive laser absorption spectroscopy, to measure trace quantities of radiation induced chemical species. We have tried proof-of-principle experiments through the off-line/on-line measurement of ⁶⁰Co gamma-ray induced NO₂ in the air. From these results, it has been verified that the present cavity ring-down measurement is quite useful as a dose rate monitoring method for intense radiation fields with high radiation resistance, where the expected performance will be the detectable range of the absorbed dose rate is from 0.5 to 2 × 10³ Gy(air)/s with the time resolution of about 30 s.
  Nuclear Science Symposium Conference Record, 2004 IEEE; 11/2004
• Conference Proceeding: Potential on liquid light guide as distributed radiation sensor

  J. Kawarabayashi, R. Mizuno, D. Inui, K. Watanabe, T. Iguchi
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  ABSTRACT: Position sensitive detectors with optical fibers are useful for one-dimensional distributed radiation sensing. There has been, however, a problem of radiation induced transmission losses and life time of the optical fibers restricting their applicability for high-level radiation environments. In order to improve the limitation of the optical fiber based radiation sensing, we propose to use a liquid light guide (LLG) with more radiation hardness than the solid one. The preliminary experiments have given us some promising results that the incident radiation emits the Cherenkov photons in the core and the position can be determined by the time-of-flight method. At present, we have confirmed that the position resolution is around 9.6 cm in a 2 m long LLG for the ⁶⁰Co gamma-ray beam with a diameter of 10 mm and no transmission loss is observed up to the dose of 2.5×10³ Gy.
  Nuclear Science Symposium Conference Record, 2004 IEEE; 11/2004
• Article: Detailed design of ex-vessel neutron yield monitor for ITER

  K. Asai, T. Iguchi, K. Watanabe, J. Kawarabayashi, T. Nishitani, C. I. Walker
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  ABSTRACT: Taking into consideration the latest design of the International Thermonuclear Experimental Reactor (ITER) main units, we have made the detailed design consideration for an ex-vessel neutron yield monitor to meet the ITER requirements. The monitoring system is constructed of four detector modules consisting of several ²³⁵ U fission chambers with different sensitivities and graphite (or beryllium) neutron moderator. We also selected possible spaces in the diagnostic ports to install them at appropriate distances and neutron shielding effects from the plasma. Through Monte Carlo neutron transport calculations, it has been confirmed that the present system can cover all the neutron yields encountered in the ITER experiments including the in situ calibrations with a time resolution around 200 μ s without detector replacement over the whole ITER experiments. This system can also be calibrated with 10% of required accuracies in a realistic 50 h of accumulation time using a DT neutron generator.
  Review of Scientific Instruments 11/2004; · 1.37 Impact Factor
• Article: Development of fusion neutron camera using organic liquid scintillator and wavelength shifting fiber

  D. Inui, T. Iguchi, K. Watanabe, J. Kawarabayashi, T. Nishitani
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  ABSTRACT: For fusion neutron profile monitoring, we propose to use a new position sensitive fast neutron detector (PSFND). We have considered an applicability of the present PSFND to two types of fusion neutron camera; a pinhole camera and a double crystal time-of-flight camera.
  Review of Scientific Instruments 10/2004; 75(10):3578-3580. · 1.37 Impact Factor
• Conference Proceeding: New position sensitive cryogenic detector with single electron transistor

  J. Kawarabayashi, K. Aoki, T. Kadoi, K.-I. Watanabe, A. Uritani, T Iguchi
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  ABSTRACT: We proposed a new micro-calorimetric detector with four single electron transistor (SET) read-out circuits that aimed the real-time detector with spatial resolution of 100 nm. The new detector consists of two layers of the micro-calorimeters. The top layer had four SETs, which worked as thermometers to decide the photoelectron position by the difference of each SET's temperature caused by heat flow in the layer. We investigated the SET performance and the heat flow in the substrate at cryogenic temperature. From calculational results, the temperature resolution of 10 mK could be achieved with a pico-ammeter having 5.0 × 10^-9S sensitivity. Also, the detector configuration achieving the 100 nm spatial and 8 μ second time resolution was successfully designed.
  Nuclear Science Symposium Conference Record, 2003 IEEE; 11/2003
• Source

  Available from: nagoya-u.ac.jp

  Article: Radiation distribution sensing with normal optical fiber

  R. Naka, K. Watanabe, J. Kawarabayashi, A. Uritani, T. Iguchi, N. Hayashi, N. Kojima, T. Yoshida, J. Kaneko, H. Takeuchi, T. Kakuta
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  ABSTRACT: The purpose of this study is to develop a radiation distribution monitor using a normal plastic optical fiber. The monitor has a long operating length and can obtain continuous radiation distributions. A principle of the position sensing is based on a time-of-flight technique. The monitor is sensitive to beta rays or charged particles, gamma rays, and fast neutrons. The spatial resolutions for beta-rays (/sup 90/Sr-/sup 90/Y), gamma-rays (/sup 137/Cs), and D-T neutrons are 30, 37, and 13 cm, respectively. The detection efficiencies for the beta-rays, gamma-rays, and D-T neutrons are 0.11%, 1.6/spl times/10/sup -5/% and 1.2/spl times/10/sup -4/%, respectively. The effective attenuation length of the detection efficiency is 18 m. In this paper, we describe the basic characteristics of this monitor.
  IEEE Transactions on Nuclear Science 01/2002; · 1.45 Impact Factor
• Conference Proceeding: Single electron transistor for cryogenic detector read-out

  J. Kawarabayashi, T. Kadoi, K.-I. Watanabe, A. Uritani, T Iguchi
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  ABSTRACT: Cryogenic detectors have been developed over the last few years in many fields. Here we proposed two types of single electron transistor read-out systems that would be able to operate in magnetic field. The one type was coupled with a super conduction tunnel junction detector and the other was coupled with a micro calorimeter. From calculation results, the coupling of the single electron transistor and the super conduction tunnel junction detector would easily detect X-rays in the configuration that the dot size and operation temperature were 200 nm square and 1.5 K respectively.
  Nuclear Science Symposium Conference Record, 2001 IEEE; 12/2001
• Article: Digital waveform analysis for 3He ionization chamber

  J. Kawarabayashi, M.P. Mardiyanto, A. Uritani, T. Iguchi, J. Kaneko, H. Takeuchi
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  ABSTRACT: Numerical analyzes on individual pulses from a cylindrical ³He gas ionization chamber have been performed. A radial distribution of the electron ion pairs was successfully analyzed by a deconvolution technique combined with a digital waveform analysis. From the charge distribution, clear separation of events of the reactions of ³He(n,p)T and ³He(n,n)³He at the energy region of the ³He recoil edge was observed
  IEEE Transactions on Nuclear Science 07/2001; · 1.45 Impact Factor
• Article: Time-of-flight neutron spectrometer for JT-60U

  Y. Shibata, T. Iguchi, M. Hoek, T. Nishitani, A. Morioka
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  ABSTRACT: The authors have developed a 2.45 MeV neutron double crystal time-of-flight (DC–TOF) spectrometer for deuterium plasmas in JT-60U. The DC–TOF neutron spectrometer consists of two fast plastic scintillators (BC-408 made by Bicron, 50 cm2 and 1800 cm2, thickness 2 cm), located on constant TOF spheres. The constant TOF spheres have a radius of 1 m which gives a neutron flight length of 1.64 m and a TOF of 92 ns for 2.45 MeV neutrons. The calculated spectrometer efficiency and resolution are 2.8×10−2 cm2 and 100 keV, respectively. The energy resolution corresponds to a time resolution of 2.0 ns. The spectrometer has been installed in the basement of JT-60U, 10 m away from the plasma center with vertical line-of-sight. Neutron energy spectra have been obtained when the neutron yield from the plasma is ∼ 1015 neutrons/s. © 2001 American Institute of Physics.
  Review of Scientific Instruments 12/2000; 72(1):828-831. · 1.37 Impact Factor
• Conference Proceeding: Digital waveform analysis for ³He ionization chamber

  J. Kawarabayashi, M.P. Mardiyanto, A. Uritani, T Iguchi, I Kaneko, H Takeuchi
  [show abstract] [hide abstract]
  ABSTRACT: Numerical analyses on individual pulses from a cylindrical ³He gas ionization chamber have been performed. A radial distribution of the electron ion pairs was successfully analyzed by a deconvolution technique combined with a digital waveform analysis. From the charge distribution, clear separation of events of the reactions of ³He(n,p)T and ³He(n,n)³He at the energy range of the ³He recoil edge was observed
  Nuclear Science Symposium Conference Record, 2000 IEEE; 02/2000
• Conference Proceeding: Micro cone detector

  D. Suyama, J. Kawarabayashi, A. Uritani, T Iguchi
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  ABSTRACT: We proposed and designed a new type of two dimensional detector that has cone shape structure. This detector consists the cone shape electrode and the hole shape electrode. A wet anisotropic etching and photolithography were performed to fabricate this detector. Simulation was performed in order to optimize the structural design and estimate the performance. From the simulation result, gas gain of 10³ to 10⁴ was obtained. Also, rise time of less than 10 micro seconds were calculated and reduction of charge accumulation on the insulator were estimated. A preliminary test fabrication was made and the signal from anode cone was successfully observed with this device
  Nuclear Science Symposium Conference Record, 2000 IEEE; 02/2000
• Source

  Available from: ac.jp

  Conference Proceeding: Radiation distribution sensing with normal optical fiber

  R. Naka, J. Kawarabayashi, A. Uritani, T. Iguchi, J. Kaneko, H. Takeuchi, T. Kakuta
  [show abstract] [hide abstract]
  ABSTRACT: The purpose of this study is to develop a radiation distribution monitor using a normal plastic optical fiber. The monitor has a long operating length and can obtain continuous radiation distributions. A principle of;the position sensing is based on a time-of-flight technique. The monitor is sensitive to beta rays or charged particles, gamma rays, and fast neutrons. The spatial resolutions for beta rays ( ⁹⁰Sr-⁹⁰Y), gamma rays (¹³⁷Cs) and D-T neutrons are 30 cm, 37 cm and 13 cm, respectively. The detection efficiencies for the beta rays, the gamma rays and D-T neutrons are 0.11%, 1.6×10^-5% and 1.2×10^-4%, respectively. The effective attenuation length of the detection efficiency is 18 m. In this paper, we describe the basic characteristics of this monitor
  Nuclear Science Symposium Conference Record, 2000 IEEE; 02/2000
• Article: Pulse shape recognition for CdZnTe semiconductor detector by using multi-shaping amplifiers method with neural network algorithm

  H. Sakai, A. Uritani, C. Mori, T. Iguchi
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  ABSTRACT: A new pulse shape recognition method with multi-shaping amplifiers, combined with a neural network algorithm, has been developed, where four pulse heights are sampled from one signal pulse through four linear amplifiers with different shaping time constants. The four pulse heights are used as characteristic parameters to recognize the pulse shape with a neural network. This method has been applied to signal processing for a CdZnTe semiconductor detector to improve the deteriorated energy spectra caused by pulse height deficits due to the different mobilities of electrons and holes in the detector. The neural network recognizes the pulse shape patterns and provides the corrective magnification factors of the pulse heights. After the corrective procedure, the energy spectrum for ¹³⁷Cs gamma-rays is improved from 9.3 keV to 7.4 keV in the energy resolution (FWHM) of the 662 keV gamma rays photopeak. The photopeak becomes a considerably symmetrical shape without a low-energy tail. It has been verified that this method is simple and useful for pulse shape analyses, which can be used for many other applications
  IEEE Transactions on Nuclear Science 09/1999; · 1.45 Impact Factor