1
|
Zhang Y, Ge L, Hu Z, Sun J, Li X, Ogawa K, Isobe M, Sangaroon S, Liao L, Yang D, Gorini G, Nocente M, Tardocchi M, Fan T. Design and optimization of an advanced time-of-flight neutron spectrometer for deuterium plasmas of the large helical device. Rev Sci Instrum 2021; 92:053547. [PMID: 34243352 DOI: 10.1063/5.0043766] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/11/2021] [Accepted: 05/08/2021] [Indexed: 06/13/2023]
Abstract
A time-of-flight neutron spectrometer based on the Time-Of-Flight Enhanced Diagnostic (TOFED) concept has been designed and is under development for the Large Helical Device (LHD). It will be the first advanced neutron spectrometer to measure the 2.45 MeV D-D neutrons (DDNs) from helical/stellarator plasmas. The main mission of the new TOFED is to study the supra-thermal deuterons generated from the auxiliary heating systems in helical plasmas by measuring the time-of-flight spectra of DDN. It will also measure the triton burnup neutrons (TBNs) from the d+t reactions, unlike the original TOFED in the EAST tokamak. Its capability of diagnosing the TBN ratios is evaluated in this work. This new TOFED is expected to be installed in the basement under the LHD hall and shares the collimator with one channel of the vertical neutron camera to define its line of sight. The distance from its primary scintillators to the equatorial plane of LHD plasmas is about 15.5 m. Based on Monte Carlo simulation by a GEANT4 model, the resolution of the DDN energy spectra is 6.6%. When projected onto the neutron rates that are typically obtained in LHD deuterium plasmas (an order of 1015 n/s with neutral beam injection), we expect to obtain the DDN and TBN counting rates of about 2.5 · 105 counts/s and 250 counts/s, respectively. This will allow us to analyze the DDN time-of-flight spectra on time scales of 0.1 s and diagnose the TBN emission rates in several seconds with one instrument, for the first time in helical/stellarator plasmas.
Collapse
Affiliation(s)
- Yimo Zhang
- State Key Laboratory of Nuclear Physics and Technology, Peking University, Beijing 100871, China
| | - Lijian Ge
- State Key Laboratory of Nuclear Physics and Technology, Peking University, Beijing 100871, China
| | - Zhimeng Hu
- State Key Laboratory of Nuclear Physics and Technology, Peking University, Beijing 100871, China
| | - Jiaqi Sun
- State Key Laboratory of Nuclear Physics and Technology, Peking University, Beijing 100871, China
| | - Xiangqing Li
- State Key Laboratory of Nuclear Physics and Technology, Peking University, Beijing 100871, China
| | - Kunihiro Ogawa
- National Institute for Fusion Science, 322-6 Oroshi-cho, Toki 509-5292, Japan
| | - Mitsutaka Isobe
- National Institute for Fusion Science, 322-6 Oroshi-cho, Toki 509-5292, Japan
| | | | - Longyong Liao
- State Key Laboratory of Nuclear Physics and Technology, Peking University, Beijing 100871, China
| | - Danke Yang
- State Key Laboratory of Nuclear Physics and Technology, Peking University, Beijing 100871, China
| | - Giuseppe Gorini
- Dipartimento di Fisica "G. Occhialini," Università degli Studi di Milano-Bicocca, Milano 20126, Italy
| | - Massimo Nocente
- Dipartimento di Fisica "G. Occhialini," Università degli Studi di Milano-Bicocca, Milano 20126, Italy
| | - Marco Tardocchi
- Institute for Plasma Science and Technology, National Research Council, Milan 20125, Italy
| | - Tieshuan Fan
- State Key Laboratory of Nuclear Physics and Technology, Peking University, Beijing 100871, China
| |
Collapse
|
2
|
Sangaroon S, Ogawa K, Isobe M, Kobayashi MI, Fujiwara Y, Kamio S, Seki R, Nuga H, Yamaguchi H, Osakabe M. Performance of the newly installed vertical neutron cameras for low neutron yield discharges in the Large Helical Device. Rev Sci Instrum 2020; 91:083505. [PMID: 32872928 DOI: 10.1063/5.0010302] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/13/2020] [Accepted: 07/24/2020] [Indexed: 06/11/2023]
Abstract
Two new vertical neutron cameras characterized by high detection efficiency were developed on the Large Helical Device in order to observe poloidal structures of helically trapped beam ions created by the perpendicularly injected positive-ion based neutral beam (P-NB) and are newly operated since 2018. In this work, the neutron fields at the vertical neutron cameras are investigated using the Monte Carlo N-particle transport code to evaluate the performance of its collimators. The results indicate that neutrons are attenuated by the heavy concrete and are well collimated through the collimator to detectors. Neutron spectra at the detector position show over 99% of uncollided 2.45 MeV neutrons. Time evolution of neutron emission profiles during the short pulse of P-NB injection is measured by the vertical neutron cameras. Peaks on the neutron emission profiles corresponding to the helically trapped beam ion are successfully obtained, as designed. The decrease in line integrated neutron flux at the peak positions after the P-NB stops is consistent with the behavior of the total neutron emission rate measured by the neutron flux monitor.
Collapse
Affiliation(s)
- S Sangaroon
- National Institute for Fusion Science, National Institutes of Natural Sciences, Toki 509-5292, Japan
| | - K Ogawa
- National Institute for Fusion Science, National Institutes of Natural Sciences, Toki 509-5292, Japan
| | - M Isobe
- National Institute for Fusion Science, National Institutes of Natural Sciences, Toki 509-5292, Japan
| | - M I Kobayashi
- National Institute for Fusion Science, National Institutes of Natural Sciences, Toki 509-5292, Japan
| | - Y Fujiwara
- National Institute for Fusion Science, National Institutes of Natural Sciences, Toki 509-5292, Japan
| | - S Kamio
- National Institute for Fusion Science, National Institutes of Natural Sciences, Toki 509-5292, Japan
| | - R Seki
- National Institute for Fusion Science, National Institutes of Natural Sciences, Toki 509-5292, Japan
| | - H Nuga
- National Institute for Fusion Science, National Institutes of Natural Sciences, Toki 509-5292, Japan
| | - H Yamaguchi
- National Institute for Fusion Science, National Institutes of Natural Sciences, Toki 509-5292, Japan
| | - M Osakabe
- National Institute for Fusion Science, National Institutes of Natural Sciences, Toki 509-5292, Japan
| |
Collapse
|
3
|
Yamada H, Tanaka K, Seki R, Suzuki C, Ida K, Fujii K, Goto M, Murakami S, Osakabe M, Tokuzawa T, Yokoyama M, Yoshinuma M. Isotope Effect on Energy Confinement Time and Thermal Transport in Neutral-Beam-Heated Stellarator-Heliotron Plasmas. Phys Rev Lett 2019; 123:185001. [PMID: 31763903 DOI: 10.1103/physrevlett.123.185001] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/02/2019] [Revised: 08/30/2019] [Indexed: 06/10/2023]
Abstract
The isotope effect on energy confinement time and thermal transport has been investigated for plasmas confined by a stellarator-heliotron magnetic field. This is the first detailed assessment of an isotope effect in a stellarator heliotron. Hydrogen and deuterium plasmas heated by neutral beam injection on the Large Helical Device have exhibited no significant dependence on the isotope mass in thermal energy confinement time, which is not consistent with the simple gyro-Bohm model. A comparison of thermal diffusivity for dimensionally similar hydrogen and deuterium plasmas in terms of the gyroradius, collisionality, and thermal pressure has clearly shown robust confinement improvement in deuterium to compensate for the unfavorable mass dependence predicted by the gyro-Bohm model.
Collapse
Affiliation(s)
- H Yamada
- National Institute for Fusion Science, National Institutes of Natural Sciences, Toki, Gifu 509-5292, Japan
- The University of Tokyo, Kashiwa, Chiba 277-8568, Japan
| | - K Tanaka
- National Institute for Fusion Science, National Institutes of Natural Sciences, Toki, Gifu 509-5292, Japan
- Kyushu University, Kasuga, Fukuoka 816-8580, Japan
| | - R Seki
- National Institute for Fusion Science, National Institutes of Natural Sciences, Toki, Gifu 509-5292, Japan
- SOKENDAI (The Graduate University for Advanced Studies), Toki, Gifu 509-5292, Japan
| | - C Suzuki
- National Institute for Fusion Science, National Institutes of Natural Sciences, Toki, Gifu 509-5292, Japan
| | - K Ida
- National Institute for Fusion Science, National Institutes of Natural Sciences, Toki, Gifu 509-5292, Japan
| | - K Fujii
- Kyoto University, Kyoto 615-8530, Japan
| | - M Goto
- National Institute for Fusion Science, National Institutes of Natural Sciences, Toki, Gifu 509-5292, Japan
- SOKENDAI (The Graduate University for Advanced Studies), Toki, Gifu 509-5292, Japan
| | | | - M Osakabe
- National Institute for Fusion Science, National Institutes of Natural Sciences, Toki, Gifu 509-5292, Japan
- SOKENDAI (The Graduate University for Advanced Studies), Toki, Gifu 509-5292, Japan
| | - T Tokuzawa
- National Institute for Fusion Science, National Institutes of Natural Sciences, Toki, Gifu 509-5292, Japan
- SOKENDAI (The Graduate University for Advanced Studies), Toki, Gifu 509-5292, Japan
| | - M Yokoyama
- National Institute for Fusion Science, National Institutes of Natural Sciences, Toki, Gifu 509-5292, Japan
- SOKENDAI (The Graduate University for Advanced Studies), Toki, Gifu 509-5292, Japan
| | - M Yoshinuma
- National Institute for Fusion Science, National Institutes of Natural Sciences, Toki, Gifu 509-5292, Japan
| |
Collapse
|
4
|
Liu Y, Morita S, Oishi T, Goto M. Effect of neutron and γ -ray on charge-coupled device for vacuum/extreme ultraviolet spectroscopy in deuterium discharges of large helical device. Rev Sci Instrum 2018; 89:10I109. [PMID: 30399678 DOI: 10.1063/1.5037233] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/22/2018] [Accepted: 06/27/2018] [Indexed: 06/08/2023]
Abstract
A charge-coupled device (CCD) is widely used as a detector of vacuum spectrometers in fusion devices. Recently, a deuterium plasma experiment has been initiated in a Large Helical Device (LHD). Totally 3.7 × 1018 neutrons have been yielded with energies of 2.45 MeV (D-D) and 14.1 MeV (D-T) during the deuterium experiment over four months. Meanwhile, γ-rays are radiated from plasma facing components and laboratory structural materials in a wide energy range, i.e., 0.01-12.0 MeV, through the neutron capture. It is well known that these neutrons and γ-rays bring serious problems to the CCD system. Then, several CCDs of vacuum ultraviolet/extreme ultraviolet/X-ray spectrometers installed at different locations on LHD for measurements of spectra and spatial profiles of impurity emission lines are examined to study the effect of neutrons and γ-rays. An additional CCD placed in a special shielding box made of 10 cm thick polyethylene contained 10% boron and 1.5 cm thick lead is also used for the detailed analysis. As a result, it is found that the CCD has no damage in the present neutron yield of LHD, while the background noise integrated for all pixels of CCD largely increases, i.e., 1-3 × 108 counts/s. The data analysis of CCD in the shielding box shows that the background noise caused by the γ-ray is smaller than that caused by the neutron, i.e., 41% from γ-rays and 59% from neutrons. It is also found that the noise can be partly removed by an accumulation of CCD frames or software programming.
Collapse
Affiliation(s)
- Y Liu
- Department of Fusion Science, Graduate University for Advanced Studies, Toki 509-5292, Gifu, Japan
| | - S Morita
- Department of Fusion Science, Graduate University for Advanced Studies, Toki 509-5292, Gifu, Japan
| | - T Oishi
- Department of Fusion Science, Graduate University for Advanced Studies, Toki 509-5292, Gifu, Japan
| | - M Goto
- Department of Fusion Science, Graduate University for Advanced Studies, Toki 509-5292, Gifu, Japan
| |
Collapse
|