DETERMINATION OF THE PLASMA DENSITY PROFILE BY MEASURING BALMER RADIATION FROM INJECTED NEUTRAL BEAMS
We present a new diagnostic technique to determine the plasma density profile by analysing the attenuation behaviour of neutral beams injected for plasma heating. The population of the surviving neutrals at a penetration depth into the plasma can be inferred from the excitation light produced primarily by electron impact. The excitation light is roughly independent of the electron temperature and easily distinguished by means of Doppler shift spectroscopy. Hydrogen neutral beams typically consist of three energy species (E, E/2, E/3) with different survival probabilities. By comparing the excitation light from each species at several points along the beam path, it is possible to decode information on the plasma density through which the beam has passed. This method is particularly attractive in that the usual Abel inversion is avoided and that the ratio of light intensities from different species is self-calibrating. The result of a proof-of-principle experiment on the Doublet III Tokamak monitoring the Balmer alpha light is presented.
Bibliographic Reference: 5TH APS TOPICAL CONFERENCE ON ATOMIC PROCESSES IN HIGH TEMPERATURE PLASMAS, PACIFIC GREWE, CALIFORNIA (USA), FEB. 25-28, 1985, PUBLISHED IN AMERICAN PHYSICAL SOCIETY BULLETIN, VOL. 30 (1985), NO. 6, P. 1128
Record Number: 1989124024300 / Last updated on: 1987-01-01
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