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Title: Improvements to the Ion Doppler Spectrometer Diagnostic on the HIT-SI Experiments

Abstract

An Ion Doppler Spectrometer diagnostic system measuring impurity ion temperature and velocity on the HIT-SI and HIT-SI3 spheromak devices has been improved with higher spatiotemporal resolution and lower error than previously described devices. Hardware and software improvements to the established technique have resulted in a record 6.9 µs temporal and <=2.8 cm spatial resolution in the midplane of each device. These allow C III and O II flow, displacement, and temperature profiles to be simultaneously observed. With 72 fused-silica fiber channels in two independent bundles, and an f/8.5 Czerny-Turner spectrometer coupled to video camera, frame-rates of up to ten times the imposed magnetic perturbation frequency of 14.5 kHz were achieved in HIT-SI, viewing the upper 1/2 of the midplane. In HIT-SI3 frame-rates of up to eight times the perturbation frequency were achieved viewing both halves of the midplane. Biorthogonal Decomposition is used as a novel filtering tool, reducing uncertainty in ion temperature from <=13 to <=5 eV (with an instrument temperature of 8-16 eV), and uncertainty in velocity from <=2 to <=1 km/s. Doppler shift and broadening is calculated via the Levenberg-Marquart algorithm, after which errors in velocity and temperature are uniquely specified. Axisymmetric temperature profiles on HIT-SI3 for Cmore » III peaked near the inboard current separatrix at approximately 40 eV are observed. Axisymmetric plasma displacement profiles have been measured on HIT-SI3, peaking at approximately 6 cm at the outboard separatrix. Both profiles agree with the upper half of the midplane observable by HIT-SI. With its complete midplane view, HIT-SI3 has unambiguously extracted axisymmetric, toroidal current dependent rotation of up to 3 km/s. Analysis of the temporal phase of the displacement uncovers a coherent structure, locked to the applied perturbation. Previously described diagnostic systems could not achieve such results.« less

Authors:
ORCiD logo [1]; ORCiD logo [1];  [1]; ORCiD logo [1]
  1. Univ. of Washington, Seattle, WA (United States)
Publication Date:
Research Org.:
Univ. of Washington, Seattle, WA (United States). HIT-Group
Sponsoring Org.:
USDOE Office of Science (SC), Fusion Energy Sciences (FES) (SC-24)
OSTI Identifier:
1422696
Alternate Identifier(s):
OSTI ID: 1425255
Grant/Contract Number:  
FG02-96ER54361
Resource Type:
Accepted Manuscript
Journal Name:
Review of Scientific Instruments
Additional Journal Information:
Journal Volume: 89; Journal Issue: 3; Journal ID: ISSN 0034-6748
Publisher:
American Institute of Physics (AIP)
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY; Ion Doppler Spectrometer; HIT-SI; Plasma Diagnostics; Spheromak

Citation Formats

Hossack, Aaron, Chandra, Rian, Everson, Christopher, and Jarboe, Thomas. Improvements to the Ion Doppler Spectrometer Diagnostic on the HIT-SI Experiments. United States: N. p., 2018. Web. doi:10.1063/1.4990432.
Hossack, Aaron, Chandra, Rian, Everson, Christopher, & Jarboe, Thomas. Improvements to the Ion Doppler Spectrometer Diagnostic on the HIT-SI Experiments. United States. doi:10.1063/1.4990432.
Hossack, Aaron, Chandra, Rian, Everson, Christopher, and Jarboe, Thomas. Fri . "Improvements to the Ion Doppler Spectrometer Diagnostic on the HIT-SI Experiments". United States. doi:10.1063/1.4990432. https://www.osti.gov/servlets/purl/1422696.
@article{osti_1422696,
title = {Improvements to the Ion Doppler Spectrometer Diagnostic on the HIT-SI Experiments},
author = {Hossack, Aaron and Chandra, Rian and Everson, Christopher and Jarboe, Thomas},
abstractNote = {An Ion Doppler Spectrometer diagnostic system measuring impurity ion temperature and velocity on the HIT-SI and HIT-SI3 spheromak devices has been improved with higher spatiotemporal resolution and lower error than previously described devices. Hardware and software improvements to the established technique have resulted in a record 6.9 µs temporal and <=2.8 cm spatial resolution in the midplane of each device. These allow C III and O II flow, displacement, and temperature profiles to be simultaneously observed. With 72 fused-silica fiber channels in two independent bundles, and an f/8.5 Czerny-Turner spectrometer coupled to video camera, frame-rates of up to ten times the imposed magnetic perturbation frequency of 14.5 kHz were achieved in HIT-SI, viewing the upper 1/2 of the midplane. In HIT-SI3 frame-rates of up to eight times the perturbation frequency were achieved viewing both halves of the midplane. Biorthogonal Decomposition is used as a novel filtering tool, reducing uncertainty in ion temperature from <=13 to <=5 eV (with an instrument temperature of 8-16 eV), and uncertainty in velocity from <=2 to <=1 km/s. Doppler shift and broadening is calculated via the Levenberg-Marquart algorithm, after which errors in velocity and temperature are uniquely specified. Axisymmetric temperature profiles on HIT-SI3 for C III peaked near the inboard current separatrix at approximately 40 eV are observed. Axisymmetric plasma displacement profiles have been measured on HIT-SI3, peaking at approximately 6 cm at the outboard separatrix. Both profiles agree with the upper half of the midplane observable by HIT-SI. With its complete midplane view, HIT-SI3 has unambiguously extracted axisymmetric, toroidal current dependent rotation of up to 3 km/s. Analysis of the temporal phase of the displacement uncovers a coherent structure, locked to the applied perturbation. Previously described diagnostic systems could not achieve such results.},
doi = {10.1063/1.4990432},
journal = {Review of Scientific Instruments},
number = 3,
volume = 89,
place = {United States},
year = {2018},
month = {3}
}

Journal Article:
Free Publicly Available Full Text
Publisher's Version of Record

Figures / Tables:

Figure 1 Figure 1: HIT-SI3 (left) and HIT-SI (right) flux conservers cut away at the toroidal midplane. Helicity injectors are shown, with flux coils (blue on HIT-SI and white on HIT-SI3) and voltage coils (red on HIT-SI and multicolored on HIT-SI3) shown separately. On HIT-SI, the second injector (‘Y’) opposes the picturedmore » one (‘X’), rotated 90° toroidally. On HIT-SI3, all injectors (‘A’,‘B’, and ‘C’) are pictured.« less

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