skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: Doppler shift measurement of Balmer-alpha line spectrum emission from a plasma in a negative hydrogen ion source

Abstract

Balmer-α light emission from the extraction region of the LHD one-third ion source has shown a characteristic Doppler broadening in the wavelength spectrum detected by a high resolution spectrometer. The spectrum resembles Gaussian distribution near the wavelength of the intensity peak, while it has an additional component of a broader foot. The measured broadening near the wavelength of the intensity peak corresponds to 0.6 eV hydrogen atom temperature. The spectrum exhibits a larger expansion in the blue wing which becomes smaller when the line of sight is tilted toward the driver region from the original observation axis parallel to the plasma grid. A surface collision simulation model predicts the possibility of hydrogen reflection at the plasma grid surface to form a broad Balmer-α light emission spectrum.

Authors:
;  [1]; ; ;  [2];  [3]
  1. Graduate School of Science and Engineering, Doshisha University, Kyotanabe, Kyoto 610-0321 Japan (Japan)
  2. National Institute for Fusion Science, Toki, Gifu (Japan)
  3. Graduate School of Frontier Sciences, The Universtiy of Tokyo, Chiba 277-8561 (Japan)
Publication Date:
OSTI Identifier:
22391394
Resource Type:
Journal Article
Resource Relation:
Journal Name: AIP Conference Proceedings; Journal Volume: 1655; Journal Issue: 1; Conference: NIBS 2014: 4. International Symposium on Negative Ions, Beams and Sources, Garching (Germany), 6-10 Oct 2014; Other Information: (c) 2015 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; 70 PLASMA PHYSICS AND FUSION TECHNOLOGY; ATOMS; COMPUTERIZED SIMULATION; DOPPLER BROADENING; EMISSION SPECTRA; EV RANGE; GAUSS FUNCTION; HYDROGEN; HYDROGEN IONS; ION SOURCES; LHD DEVICE; PLASMA; REFLECTION; SURFACES; VISIBLE RADIATION

Citation Formats

Wada, M., E-mail: mwada@mail.doshisha.ac.jp, Doi, K., Kisaki, M., Nakano, H., Tsumori, K., and Nishiura, M. Doppler shift measurement of Balmer-alpha line spectrum emission from a plasma in a negative hydrogen ion source. United States: N. p., 2015. Web. doi:10.1063/1.4916411.
Wada, M., E-mail: mwada@mail.doshisha.ac.jp, Doi, K., Kisaki, M., Nakano, H., Tsumori, K., & Nishiura, M. Doppler shift measurement of Balmer-alpha line spectrum emission from a plasma in a negative hydrogen ion source. United States. doi:10.1063/1.4916411.
Wada, M., E-mail: mwada@mail.doshisha.ac.jp, Doi, K., Kisaki, M., Nakano, H., Tsumori, K., and Nishiura, M. Wed . "Doppler shift measurement of Balmer-alpha line spectrum emission from a plasma in a negative hydrogen ion source". United States. doi:10.1063/1.4916411.
@article{osti_22391394,
title = {Doppler shift measurement of Balmer-alpha line spectrum emission from a plasma in a negative hydrogen ion source},
author = {Wada, M., E-mail: mwada@mail.doshisha.ac.jp and Doi, K. and Kisaki, M. and Nakano, H. and Tsumori, K. and Nishiura, M.},
abstractNote = {Balmer-α light emission from the extraction region of the LHD one-third ion source has shown a characteristic Doppler broadening in the wavelength spectrum detected by a high resolution spectrometer. The spectrum resembles Gaussian distribution near the wavelength of the intensity peak, while it has an additional component of a broader foot. The measured broadening near the wavelength of the intensity peak corresponds to 0.6 eV hydrogen atom temperature. The spectrum exhibits a larger expansion in the blue wing which becomes smaller when the line of sight is tilted toward the driver region from the original observation axis parallel to the plasma grid. A surface collision simulation model predicts the possibility of hydrogen reflection at the plasma grid surface to form a broad Balmer-α light emission spectrum.},
doi = {10.1063/1.4916411},
journal = {AIP Conference Proceedings},
number = 1,
volume = 1655,
place = {United States},
year = {Wed Apr 08 00:00:00 EDT 2015},
month = {Wed Apr 08 00:00:00 EDT 2015}
}
  • The structure of the hydrogen Balmer-alpha line emission profiles from three types of neutral-beam-injector ion-source plasmas (filling pressure approx.10 mTorr, electron density approx.(1--2) x 10/sup 12/ cm/sup -3/, electron temperature approx.2--4 eV) is studied with the aid of a simple model for the neutral-particle balance and H/sub ..cap alpha../ emission. This model includes molecular and atomic reactions, wall interactions, and nonthermal electrons. A large fraction of the H/sub ..cap alpha../ is produced by dissociative excitation of H/sub 2/ and dissociative recombination of H/sub 2/ /sup +/, while the remainder is produced by excitation of H atoms, most of which havemore » energies that are close to the characteristics H/sub 2/ dissociation energies. The H/sub ..cap alpha../ linewidth is thus insensitive to the discharge operating conditions and equals approx.0.27 A when only slow (approx.0.3 eV) dissociatively excited atoms are present or approx.0.35 A when fast (>1 eV) atoms, apparently also produced in dissociation reactions, are present as well.« less
  • The velocity spectra of the negative-ion-(H{sup -}) based neutral beams are studied in high-performance large-area ion sources during injection into large helical device fusion plasmas. We are conducting systematic observations in standard neutral beam injection to correlate beam spectra with source operating conditions. Almost all of the transmitted beam power was at full acceleration energy ({approx}170 keV). The small stripping beam component which was produced in the extraction gap was evaluated to be about 9%-22% by amplitude of the measured spectra for the sources in beam lines 1 and 2. H{sup -} production uniformity from the spectrum profile was 86%-90%more » for three sources. For the longest pulse injection during 74 and 128 s, a full energy component tended to decrease with time, while the accelerator gap stripping tail tended to increase slightly with time, which is attributed to beam-induced outgassing in the accelerator. A higher conductance multislot ground grid accelerator appeared to show little growth in the accelerator gap beam stripping during long pulses compared to the conventional multiaperture ground grid. The beam uniformity appeared to vary in part with the Cs uniformity on the plasma grid.« less
  • Vacuum ultra violet (VUV) emission spectra from plasmas near walls of different metallic materials were measured to estimate the effect upon the local production rate of vibrational excited hydrogen molecules due to plasma wall interaction. Among Cu, Mo, Ni, Ta and Ti, the intensity of band spectrum around Lyman-{alpha} had become the largest when Cu wall was used while it was the smallest for Ti. The role of particle reflection from the plasma electrode surface upon the H{sup -} production by a pure electron volume process is discussed.
  • At CERN, a non caesiated H{sup -} ion volume source derived from the DESY ion source is being commissioned. For a proposed High Power Superconducting Proton Linac (HP-SPL), a non caesiated plasma generator was designed to operate at the two orders of magnitude larger duty factor required by the SPL. The commissioning of the plasma generator test stand and the plasma generator prototype are completed and briefly described. The 2 MHz RF generators (100 kW, 50 Hz repetition rate) was successfully commissioned; its frequency and power will be controlled by arbitrary function generators during the 1 ms plasma pulse. Inmore » order to characterize the plasma, RF-coupling, optical spectrometer, rest gas analyzer and Langmuir probe measurements will be used. Optical spectrometry allows direct comparison with the currently commissioned Linac4 H{sup -} ion source plasma. The first measurements of the optical emission of the Linac4 ion source and of the SPL plasma generator plasmas are presented.« less