Investigation of ^3He ICRF Heating Schemes at 8 T in Alcator C-Mod
Abstract
^3He minority and D(^3He) mode converstion heating are the main heating scenarios for high field operation of C-Mod. Efficient heating at high field is essential for the C-Mod research program. The ^3He minority scenario has been successfully demonstrated on several tokamaks. Exploratory experiments in previous campaigns found improved power absorption (up to 70%) in a boronized machine. However, it appears to be significantly less efficient than D(H) heating ( ~90%). Furthermore, a clear sign of electron heating by ^3He minority tail has not been observed except at very low concentration (<1%). Rather at relatively low ^3He concentrations (<5%), significant direct electron heating has been observed. The power absorbed by electrons is measured by direct break-in-slope or Fourier analysis of local electron temperature. For central electron heating from tail ions, the sawtooth reheat is analyzed to calculate the power transfered to electrons from collisions with fast ions. The total power absorbed is estimated from break-in-slope analysis of the stored plasma energy. Results from a ^3He concentration scan experiment and a comparison to TORIC and FPPRF will be presented.
- Publication:
-
APS Division of Plasma Physics Meeting Abstracts
- Pub Date:
- November 1997
- Bibcode:
- 1997APS..DPPhTO105W