Fast neutron detection under intense -ray fields with novel nuclear emulsion technique

Ishihara, Kohei*; Takagi, Keisuke*; Minato, Haruna*; Kawarabayashi, Jun*; Tomita, Hideki*; Maeda, Shigetaka; Naka, Tatsuhiro*; Morishima, Kunihiro*; Nakano, Toshiyuki*; Nakamura, Mitsuhiro*; et al.

Radiation Measurements, 55, p.79 - 82, 2013/08

https://doi.org/10.1016/j.radmeas.2012.10.019

In order to measure the neutron under a condition of high intensity of -ray background, we made new nuclear emulsion based on non-sensitized OPERA emulsion which had small AgBr grain size (AgBr grain size of 60, 90 and 160 nm). The sensitivity of this new emulsion, which was a correlation between stopping power and grain density, was estimated experimentally by irradiating neutrons with several energies. We also simulated the response to -ray induced electrons and compared with some experimental results by using Co source. The results showed that there might be a threshold energy deposited in one AgBr grain under which it was impossible to develop. We estimated efficiency to the -ray and the neutron with this obtained response of the new emulsion.

Multi-scattering time-of-flight neutron spectrometer for deuterium to tritium fuel ratio measurement in fusion experimental reactors

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

https://doi.org/10.1016/j.fusengdes.2008.08.002

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.

Design consideration for high-energy-resolution neutron spectrometer based on associated particle detection using proton recoil telescope and time-of-flight technique for ITER

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

https://doi.org/10.1063/1.2221691

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%.

Feasibility Study on the High Reliable Radiation Detection System using Normal Optical Fiber

Tsujimura, Norio; Yoshida, T.; Kawarabayashi, Jun*; Mizuno, Ryoji*; Naka, Ryotaro*; Uritani, Akira*; Watanabe, Kenichi*

JNC TY8400 2003-010, 46 Pages, 2003/03

JNC-TY8400-2003-010.pdf:1.36MB

The authors developed a radiation distribution monitor using a normal optical fiber. This monitor has long operation length (10m - 100m) and can obtain continuous radiation distribution.

Basic study on development of neutron spectrometer based on multiple-scattering TOF for D/T burning ratio measurement

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.

Development of neutron spectrometer based on associated particles coincident counting for burning plasma diagnostics

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.

Applicability of multi-scattering time-of-flight neutron spectrometer to measure the fuel density ratio in experimental fusion reactor

Yukawa, Kyohei*; Asai, Keisuke*; Tomita, Hideki*; Iguchi, Tetsuo*; Iwai, Haruki*; Kawarabayashi, Jun*; Konno, Chikara

no journal, , 

We are developing 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) at the Fusion Neutronics Source, Japan Atomic Energy Agency, which includes a small amount of DD neutrons.

Sensitivity control of nuclear emulsion using AgBr nano-grains

Ishihara, Kohei*; Takagi, Keisuke*; Kawarabayashi, Jun*; Tomita, Hideki*; Naka, Tatsuhiro*; Asada, Takashi*; Morishima, Kunihiro*; Nakamura, Mitsuhiro*; Kuge, Kenichi*; Maeda, Shigetaka; et al.

no journal, , 

The nuclear emulsion with AgBr nano-grains has been developed for neutron detection under high -ray background. It has been demonstrated that the detection sensitivity of -rays can be well suppressed compared to that of neutrons by adjusting the size of AgBr nano-grains to deposit the energy of the secondary electrons produced by -rays below a certain threshold which can create Ag latent images.

Development of neutron spectrum measurement in high field using new nuclear emulsion, 2; Recognition algorithm for recoiled proton track based on three dimensional analysis of the novel nuclear emulsion

Takagi, Keisuke*; Ishihara, Kohei*; Tomita, Hideki*; Kawarabayashi, Jun*; Iguchi, Tetsuo*; Morishima, Kunihiro*; Maeda, Shigetaka; Matsumoto, Tetsuro*

no journal, , 

In the novel nuclear emulsion development to measurement a neutron spectrum in high -ray field, in order to control -ray sensitivity, the ArBr grains of about 100 nm of particle diameter is used. The recoil proton track induced by neutron is recorded on nuclear emulsion. The track constituted by a silver grains child standing in a row discretely is recorded. The track extraction algorithm suitable for extraction of recoil proton was developed, and the characteristic was evaluated.

Temperature dependence of -ray and neutron sensitivities of nuclear emulsion with AgBr nano-grains

Ishihara, Kohei*; Kawarabayashi, Jun*; Tomita, Hideki*; Naka, Tatsuhiro*; Asada, Takashi*; Morishima, Kunihiro*; Nakamura, Mitsuhiro*; Maeda, Shigetaka; Iguchi, Tetsuo*

no journal, , 

In order to establish a neutron spectrum measurement in high field such as spent nuclear fuel storage, advanced nuclear emulsion based on non-sensitized OPERA film with AgBr grain size of 60 nm has been developed. A nuclear emulsion has the feature of being easy to cause latent image degradation in the high temperature condition. In this study, the experiment estimated the temperature dependency of the sensitivity to the ray and neutron of a new nuclear emulsion. It is confirmed that the detection efficiency for a neutron and fell in more than 30 C environment.