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Title: Diagnosis of fast ions produced by negative-ion neutral-beam injection with fast-ion deuterium-alpha spectroscopy

Abstract

Negative neutral-beam injection (NNBI) is an important source of heating and current drive for next-step devices like JT-60SA and ITER where the injected energy can range from hundreds of keV to 1 MeV. Few diagnostics are suitable for phase-space resolved measurements of fast ions with energy in excess of 100 keV. A feasibility study of using fast-ion deuterium-alpha (FIDA) spectroscopy to diagnose the high-energy ions produced by NNBI in a fusion plasma is presented. Two case studies with the Large Helical Device (LHD) and JT-60SA illustrate possible solutions for the measurement. The steady-state slowing-down distribution function of fast ions produced by NNBI is calculated for both devices, and the FIDA spectrum is predicted by synthetic diagnostic simulation. Results with 180-keV NNBI in LHD show that, with a judicious choice of viewing geometry, the FIDA intensity is comparable to that obtained with the existing FIDA system. The typical time resolution of ~10 ms achieved with existing FIDA systems can be obtained with NNBI FIDA on LHD. The measurement is more challenging with the 500-keV NNBI in JT-60SA. In this case, simulations predict the FIDA intensity to be about 1% of the background bremsstrahlung, which is small compared to existing FIDA implementationsmore » with positive neutral-beam injection where signal levels are an order of magnitude larger. The sampling time required to extract the small FIDA signal is determined using a probabilistic approach. Results indicate that long averaging periods, from ones to tens of seconds, depending on the FIDA and background variance, are needed to resolve the FIDA signal in JT-60SA. These long averaging times are suitable in long-pulse (~ 100s), steady-state devices like JT-60SA where an important measurement objective is the spatial profile of the slowing-down distribution of fast ions.« less

Authors:
ORCiD logo [1];  [2];  [1]; ORCiD logo [1];  [1];  [3];  [3]
  1. General Atomics, San Diego, CA (United States)
  2. Univ. of California-Irvine, Irvine, CA (United States). Dept. of Physics and Astronomy
  3. National Inst. for Fusion Science, Toki, Gifu (Japan)
Publication Date:
Research Org.:
U.S. Dept. of Energy (USDOE), Washington D.C. (United States); General Atomics, San Diego, CA (United States); Univ. of California, Irvine, CA (United States); National Inst. for Fusion Science (NIFS) (Japan)
Sponsoring Org.:
USDOE Office of Science (SC), Fusion Energy Sciences (FES) (SC-24)
OSTI Identifier:
1568811
Alternate Identifier(s):
OSTI ID: 1544449; OSTI ID: 1595475
Grant/Contract Number:  
FC02-04ER54698; SC0018107
Resource Type:
Accepted Manuscript
Journal Name:
Review of Scientific Instruments
Additional Journal Information:
Journal Volume: 90; Journal Issue: 7; Journal ID: ISSN 0034-6748
Publisher:
American Institute of Physics (AIP)
Country of Publication:
United States
Language:
English
Subject:
47 OTHER INSTRUMENTATION; 70 PLASMA PHYSICS AND FUSION TECHNOLOGY; tokamak, fusion, magnetic confinement, energetic particles, fast ions, spectroscopy, neutral beam injection, fusion diagnostic

Citation Formats

Muscatello, C. M., Heidbrink, W. W., Boivin, R. L., Chrystal, C., Collins, C. S., Fujiwara, Y., and Yamaguchi, H. Diagnosis of fast ions produced by negative-ion neutral-beam injection with fast-ion deuterium-alpha spectroscopy. United States: N. p., 2019. Web. doi:10.1063/1.5099491.
Muscatello, C. M., Heidbrink, W. W., Boivin, R. L., Chrystal, C., Collins, C. S., Fujiwara, Y., & Yamaguchi, H. Diagnosis of fast ions produced by negative-ion neutral-beam injection with fast-ion deuterium-alpha spectroscopy. United States. doi:10.1063/1.5099491.
Muscatello, C. M., Heidbrink, W. W., Boivin, R. L., Chrystal, C., Collins, C. S., Fujiwara, Y., and Yamaguchi, H. Tue . "Diagnosis of fast ions produced by negative-ion neutral-beam injection with fast-ion deuterium-alpha spectroscopy". United States. doi:10.1063/1.5099491.
@article{osti_1568811,
title = {Diagnosis of fast ions produced by negative-ion neutral-beam injection with fast-ion deuterium-alpha spectroscopy},
author = {Muscatello, C. M. and Heidbrink, W. W. and Boivin, R. L. and Chrystal, C. and Collins, C. S. and Fujiwara, Y. and Yamaguchi, H.},
abstractNote = {Negative neutral-beam injection (NNBI) is an important source of heating and current drive for next-step devices like JT-60SA and ITER where the injected energy can range from hundreds of keV to 1 MeV. Few diagnostics are suitable for phase-space resolved measurements of fast ions with energy in excess of 100 keV. A feasibility study of using fast-ion deuterium-alpha (FIDA) spectroscopy to diagnose the high-energy ions produced by NNBI in a fusion plasma is presented. Two case studies with the Large Helical Device (LHD) and JT-60SA illustrate possible solutions for the measurement. The steady-state slowing-down distribution function of fast ions produced by NNBI is calculated for both devices, and the FIDA spectrum is predicted by synthetic diagnostic simulation. Results with 180-keV NNBI in LHD show that, with a judicious choice of viewing geometry, the FIDA intensity is comparable to that obtained with the existing FIDA system. The typical time resolution of ~10 ms achieved with existing FIDA systems can be obtained with NNBI FIDA on LHD. The measurement is more challenging with the 500-keV NNBI in JT-60SA. In this case, simulations predict the FIDA intensity to be about 1% of the background bremsstrahlung, which is small compared to existing FIDA implementations with positive neutral-beam injection where signal levels are an order of magnitude larger. The sampling time required to extract the small FIDA signal is determined using a probabilistic approach. Results indicate that long averaging periods, from ones to tens of seconds, depending on the FIDA and background variance, are needed to resolve the FIDA signal in JT-60SA. These long averaging times are suitable in long-pulse (~ 100s), steady-state devices like JT-60SA where an important measurement objective is the spatial profile of the slowing-down distribution of fast ions.},
doi = {10.1063/1.5099491},
journal = {Review of Scientific Instruments},
number = 7,
volume = 90,
place = {United States},
year = {2019},
month = {7}
}

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