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Asai, Keisuke*; Yukawa, Kyohei*; Iguchi, Tetsuo*; Naoi, Norihiro*; Watanabe, Kenichi*; Kawarabayashi, Jun*; Yamauchi, Michinori*; Konno, Chikara
Fusion Engineering and Design, 83(10-12), p.1818 - 1821, 2008/12
Times Cited Count：0 Percentile：0.01(Nuclear Science & Technology)The fuel ratio in a DT burning plasma can be derived from the intensity ratio of DD/DT neutrons, and detecting a trace of DD neutrons in the DT burning plasma is a key issue. A new type of neutron spectrometer is proposed to monitor the fuel ratio in the core of the ITER plasma. The system based on a conventional time-of-flight method consists of a water cell as a neutron scattering material and tens of scintillator pairs arranged around the first scintillator in a corn shape. We call it a multi-scattering time-of-flight neutron spectrometer (MS-TOF). A trial experiment was conducted for the prototype MS-TOF system with a DT neutron beam (20-mm diameter) at the Fusion Neutronics Source (FNS), Japan Atomic Energy Agency. The experimental results show that the DD and DT neutron peaks are clearly observed, and the experiment has successfully demonstrated the feasibility of the MS-TOF concept for detecting trace-DD neutrons within a DT neutron beam extracted from a DT burn plasma.
Asai, Keisuke*; Naoi, Norihiro*; Iguchi, Tetsuo*; Watanabe, Kenichi*; Kawarabayashi, Jun*; Nishitani, Takeo
Review of Scientific Instruments, 77(10), p.10E721_1 - 10E721_3, 2006/10
Times Cited Count：3 Percentile：20.25(Instruments & Instrumentation)A time-of-flight (TOF) neutron spectrometer is one of the candidates of the measurement of the D/T burning ratio in ITER. In the ITER high power experiments, the TOF system would suffer from high event rate or accidental counts due to high radiation intensities, which can be one of background sources for DD neutron measurement. We 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 about 3 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 and the basic performances of this system have been verified through a preliminary experiment using a DT neutron beam (20 mm
) at the Fusion Neutronics Source, Japan Atomic Energy Agency.
Naoi, Norihiro*; Asai, Keisuke*; Iguchi, Tetsuo*; Watanabe, Kenichi*; Kawarabayashi, Jun*; Nishitani, Takeo
Review of Scientific Instruments, 77(10), p.10E704_1 - 10E704_3, 2006/10
Times Cited Count：5 Percentile：29.76(Instruments & Instrumentation)The high-energy-resolution neutron spectrometry is a useful method to obtain the ion temperature and velocity distribution in nuclear fusion and/or burn plasmas. For ion temperature measurement in the ITER, we propose a promising neutron spectrometer with high-energy-resolution based on the associated particle detection using a proton recoil telescope (PRT) and a time-of-flight spectrometer (TOF). In a general PRT or TOF spectrometer, uncertainty of incident angles of recoiled protons or scattered neutrons incoming to rear detector, respectively, is a cause of deterioration of their energy resolution. In this system, no angular information is required to obtain the incident neutron energy. It is possible to enlarge the solid angles of the rear detectors subtended by the radiator to increase the detection efficiency without deterioration of the energy resolution. To verify the operational principle and the basic performance of this system, we have constructed a prototype system through Monte Carlo simulations and carried out a preliminary experiment with a deuterium-tritium neutron beam at the Fusion Neutronics Source (FNS), JAEA to obtain the energy resolution around 3.3% (in FWHM) for DT neutrons. As a result of the study for the experiment, it is expected that this system can be applied to ITER at the power within 1 order of magnitude of the maximum with measurement accuracy better than 10%.
Asai, Keisuke*; Naoi, Norihiro*; Iguchi, Tetsuo*; Watanabe, Kenichi*; Kawarabayashi, Jun*; Nishitani, Takeo
no journal, ,
Neutron spectroscopic technique can be applied to the measurement of fuel ratio, that is, deuterium and tritium densities, in the ITER plasma core. We have been developing a new time-of-flight neutron spectrometer that has a radiator in front of a pair of crystal. The radiator has a larger cross section of elastic scattering and acts as a neutron scattering material to enhance the DD/DT ratio of neutron before entering the TOF crystal. We produced a prototype system that has a water cell, 2 cm in diameter and 5 cm in thickness, as a radiator. The system performance such as detection efficiency and energy resolution were examined through an experiment with a DT neutron beam, FNS JAEA, and the experimental results agreed with simulated results.
Asai, Keisuke*; Naoi, Norihiro*; Iguchi, Tetsuo*; Watanabe, Kenichi*; Kawarabayashi, Jun*; Konno, Chikara
no journal, ,
We have been developing a time-of-flight neutron spectrometer to measure the fuel ratio in burning plasma core. This system consists of a water cell and a pair of scintillators. The water cell is inserted before the scintillator pair. The pair of scintillators is used to measure the flight time of the scattered neutron from the water cell. Elastic scattering with hydrogen nuclei in the water cell enhances the DD/DT neutron ratio and make the detection of DD neutron easier. We have considered the system configuration by Monte Carlo simulations and clarified the expected measurement accuracy and time resolution in the upper region of the ITER DT phase. This system is expected to achieve a time resolution of a few seconds with 20% accuracy for a measurement of the intensity ratio of DD/DT neutron at the ITER full power operation.
Naoi, Norihiro*; Asai, Keisuke*; Iguchi, Tetsuo*; Watanabe, Kenichi*; Kawarabayashi, Jun*; Nishitani, Takeo
no journal, ,
The energy spectrum of the neutrons in burning plasma provides information on the ion temperature and the ion energy distributions of the fuel ions. The neutron spectroscopic technique is a useful method to obtain the ion temperature and velocity distribution in the plasma core. For ion temperature measurement in the ITER high power operation phase, we propose a promising high-energy-resolution neutron spectrometer based on the associated particle detection using a proton recoil telescope and a time-of-flight spectrometer. We have carried out a preliminary experiment with a deuterium-tritium (DT) neutron beam at the Fusion Neutronics Source (FNS), JAEA, and an energy resolution of about 3% (in FWHM) was achieved for DT neutrons.
Naoi, Norihiro*; Asai, Keisuke*; Iguchi, Tetsuo*; Watanabe, Kenichi*; Kawarabayashi, Jun*; Konno, Chikara
no journal, ,
Neutron spectrometry in a fusion reactor is a useful method to obtain the fuel ratio in the plasma core. The fuel ratio is derived from the intensity ratio of DD and DT neutron that are generated from DD and DT fusion reactions, respectively. Since the typical generation of DD neutrons is appropriately 0.5% of total neutrons, high energy resolution is important as well as detection efficiency to obtain enough SNR (Signal-to-Noise Ratio) for DD neutron detection. The design of the Associated Particle Coincident Counting Neutron Spectrometer (APCC-NS) developed to measure the ion temperature in the burning plasma was revised so that the system has an enough efficiency for DD neutrons, and the performance of the system was tested with the DD neutron beam at Fusion Neutronic Source (FNS), JAEA. As a result, a time resolution to satisfy 20% accuracy of fuel ratio measurement was obtained, but further improvement turned out to be necessary for the control of the fuel injection system.
Iwai, Haruki*; Naoi, Norihiro*; Asai, Keisuke*; Iguchi, Tetsuo*; Isobe, Mitsutaka*; Yukawa, Kyohei*; Kawarabayashi, Jun*; Konno, Chikara
no journal, ,
For ion temperature measurement in DD plasma experiments, we are developing a high energy resolution neutron spectrometer based on the associated particle detection using a proton recoil telescope and a time-of-flight spectrometer. To verify the operational principle and the basic performance of this system, we have set up a prototype system through Monte Carlo simulations and carried out a preliminary experiment with a DD neutron beam at the Fusion Neutronics Source (FNS), JAEA. The results have demonstrated that the energy resolution could be achieved around 5.0% (in FWHM) for DD neutrons
