Measurements of Beam Ion Loss from the Compact Helical System

D. S. Darrow, M. Isobe, Takashi Kondo, M. Sasao, and the CHS Group National Institute for Fusion Science, Toki, Gifu, Japan

Princeton University. Plasma Physics Laboratory.

关键词: Turbulence Helical Devices, Stellarators Chs, Neutral Beams;    70 Plasma Physics And Fusion Technology;    Geometry;    Helical Devices, Stellarators Chs, Neutral Beams;    Simulation;   

DOI  :  10.2172/973204
RP-ID  :  PPPL-4500
RP-ID  :  DE-ACO2-09CH11466
RP-ID  :  973204

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来源: UNT Digital Library

【 摘 要 】

Beam ion loss from the Compact Helical System (CHS) has been measured with a scintillator-type probe. The total loss to the probe, and the pitch angle and gyroradius distributions of that loss, have been measured as various plasma parameters were scanned. Three classes of beam ion loss were observed at the probe position: passing ions with pitch angles within 10o of those of transition orbits, ions on transition orbits, and ions on trapped orbits, typically 15o or more from transition orbits. Some orbit calculations in this geometry have been performed in order to understand the characteristics of the loss. Simulation of the detector signal based upon the following of orbits from realistic beam deposition profiles is not able to reproduce the pitch angle distribution of the losses measured. Consequently it is inferred that internal plasma processes, whether magnetohydrodynamic modes, radial electric fields, or plasma turbulence, move previously confined beam ions to transition orbits, resulting in their loss.