Study of volume recombination and radiation opacity effects in Alcator C-Mod

Journal Article · Mon Sep 28 04:00:00 EDT 1998 · AIP Conference Proceedings

DOI:https://doi.org/10.1063/1.56565· OSTI ID:21202607

Terry, J L; Lipschultz, B; Pigarov, A Yu; Boswell, C; Krasheninnikov, S I; LaBombard, B; Pappas, D A ^[1]

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1. Plasma Science and Fusion Center, Massachusetts Institute of Technology, Cambridge, Massachusetts, 02139 (United States)

Observations of significant volume recombination within the Alcator C-Mod divertor plasma and in the edge plasma (MARFE) are described. The recombination occurs in regions where T{sub e} <or approx. 1 eV and n{sub e} > or approx. 1x10{sup 21} m{sup -3}. The determinations of the recombination rates are made by measuring the D{sup 0} Lyman and/or Balmer spectra and by using a collisional radiative model describing the level populations, ionization and recombination of D{sup 0}. In regions of strong recombination the upper levels (n > or approx. 4) populations are close to those determined by Saha-Boltzmann distribution and are independent of the ground state density. Thus the intensities of lines from these levels are related to the recombination rate, and curves determining the number of 'recombinations per photon' are calculated. Ly{sub {beta}} line emission is shown to be trapped in some cases, meaning that Ly{sub {alpha}} can be strongly trapped. Since opacity affects the recombination rates, the effects of the trapping of Ly{sub {alpha}}{sub ,{beta}} photons on the 'recombinations per photon' curves are calculated and considered in the recombination rate determinations. Total recombination rates in the detached divertor plasma and in MARFEs located at the periphery of the main plasma are determined. Recombination can be a significant sink for ions.

• OSTI ID: 21202607
• Journal Information: AIP Conference Proceedings, Journal Name: AIP Conference Proceedings Journal Issue: 1 Vol. 443; ISSN 0094-243X; ISSN APCPCS
• Country of Publication: United States
• Language: English

Related Subjects

70 PLASMA PHYSICS AND FUSION TECHNOLOGY
ALCATOR DEVICE
BALMER LINES
DIVERTORS
ELECTRON DENSITY
ELECTRON TEMPERATURE
EMISSION SPECTRA
EV RANGE
GROUND STATES
IONIZATION
IONS
MARFE
OPACITY
PHOTONS
PLASMA
PLASMA DIAGNOSTICS
RECOMBINATION
TRAPPING