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Title: High resolution magnetic field measurements in hydrogen and helium plasmas using active laser spectroscopy

Abstract

Passive spectroscopic measurements of Zeeman splitting have been used reliably to measure magnetic fields in plasmas for decades. However, a requirement is that the field magnitude must be sufficiently strong to be resolved over Doppler and instrument broadening (typically >10 000 G). A diagnostic for measuring magnetic fields spectroscopically well below this limit (>20 G) with high sensitivity has been developed at the Oak Ridge National Laboratory. The diagnostic relies on measuring a high resolution spectral profile using Doppler-free saturation spectroscopy (DFSS) and then fitting the spectrum to a quantum mechanical model. DFSS is an active, laser based technique that greatly reduces the influence of Doppler broadening and eliminates instrument broadening. To date, the diagnostic has been successfully employed to measure the magnetic field in magnetized (550-900 G), low-temperature (5-10 eV), low-density (10 10–10 12 cm –3), hydrogen and helium plasmas in the 5-200 mTorr pressure range using a low power (25 mW) diode laser. Implementing an approximate crossover resonance model, the measurements are shown to be accurate within 5 G for helium and 83 G for hydrogen. The accuracy in hydrogen can be improved to 39 G if the crossover resonances are neglected. As a result, a more robustmore » crossover model can decrease this error to <1 G.« less

Authors:
 [1]; ORCiD logo [2]; ORCiD logo [1]
  1. North Carolina State Univ., Raleigh, NC (United States)
  2. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
Publication Date:
Research Org.:
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
Sponsoring Org.:
USDOE
OSTI Identifier:
1482458
Grant/Contract Number:  
[AC05-00OR22725]
Resource Type:
Accepted Manuscript
Journal Name:
Review of Scientific Instruments
Additional Journal Information:
[ Journal Volume: 89; Journal Issue: 10]; Journal ID: ISSN 0034-6748
Publisher:
American Institute of Physics (AIP)
Country of Publication:
United States
Language:
English
Subject:
47 OTHER INSTRUMENTATION

Citation Formats

Zafar, Abdullah, Martin, Elijah H., and Shannon, Steve C. High resolution magnetic field measurements in hydrogen and helium plasmas using active laser spectroscopy. United States: N. p., 2018. Web. doi:10.1063/1.5039334.
Zafar, Abdullah, Martin, Elijah H., & Shannon, Steve C. High resolution magnetic field measurements in hydrogen and helium plasmas using active laser spectroscopy. United States. doi:10.1063/1.5039334.
Zafar, Abdullah, Martin, Elijah H., and Shannon, Steve C. Mon . "High resolution magnetic field measurements in hydrogen and helium plasmas using active laser spectroscopy". United States. doi:10.1063/1.5039334. https://www.osti.gov/servlets/purl/1482458.
@article{osti_1482458,
title = {High resolution magnetic field measurements in hydrogen and helium plasmas using active laser spectroscopy},
author = {Zafar, Abdullah and Martin, Elijah H. and Shannon, Steve C.},
abstractNote = {Passive spectroscopic measurements of Zeeman splitting have been used reliably to measure magnetic fields in plasmas for decades. However, a requirement is that the field magnitude must be sufficiently strong to be resolved over Doppler and instrument broadening (typically >10 000 G). A diagnostic for measuring magnetic fields spectroscopically well below this limit (>20 G) with high sensitivity has been developed at the Oak Ridge National Laboratory. The diagnostic relies on measuring a high resolution spectral profile using Doppler-free saturation spectroscopy (DFSS) and then fitting the spectrum to a quantum mechanical model. DFSS is an active, laser based technique that greatly reduces the influence of Doppler broadening and eliminates instrument broadening. To date, the diagnostic has been successfully employed to measure the magnetic field in magnetized (550-900 G), low-temperature (5-10 eV), low-density (1010–1012 cm–3), hydrogen and helium plasmas in the 5-200 mTorr pressure range using a low power (25 mW) diode laser. Implementing an approximate crossover resonance model, the measurements are shown to be accurate within 5 G for helium and 83 G for hydrogen. The accuracy in hydrogen can be improved to 39 G if the crossover resonances are neglected. As a result, a more robust crossover model can decrease this error to <1 G.},
doi = {10.1063/1.5039334},
journal = {Review of Scientific Instruments},
number = [10],
volume = [89],
place = {United States},
year = {2018},
month = {10}
}

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

Figures / Tables:

FIG. 1 FIG. 1: H$α$ Doppler-broadened spectrum (black curve) along with the fine-structure transitions (blue lines). A non-magnetized (top) and 1,000 G magnetic field (bottom) spectrum is presented to highlight the change in the fine-structure. A radiator temperature of 3,000 K was considered for the Doppler-broadened calculation.

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Works referenced in this record:

A temporally and spatially resolved electron density diagnostic method for the edge plasma based on Stark broadening
journal, July 2016

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  • Review of Scientific Instruments, Vol. 87, Issue 11
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    Figures/Tables have been extracted from DOE-funded journal article accepted manuscripts.