Profile Modifications Resulting from Early High-harmonic Fast Wave heating in NSTX

Mendard, J.E. ; LeBlanc, Wilson, J.R. ; Sabbagh, S.A. ; Stutman, D. ; and Swain, D.W.

Princeton University. Plasma Physics Laboratory.

关键词: Safety Engineering;    Beam Injection;    Heating;    Nstx Device;    70 Plasma Physics And Fusion Technology;   

DOI  :  10.2172/784550
RP-ID  :  PPPL-3564
RP-ID  :  AC02-76CH03073
RP-ID  :  784550

美国|英语

来源: UNT Digital Library

【 摘 要 】

Experiments have been performed in the National Spherical Torus Experiment (NSTX) to inject high harmonic fast wave (HHFW) power early during the plasma current ramp-up in an attempt to reduce the current penetration rate to raise the central safety factor during the flattop phase of the discharge. To date, up to 2 MW of HHFW power has been coupled to deuterium plasmas as early as t = 50 ms using the slowest interstrap phasing of k|| approximately equals 14 m(superscript)-1 (nf = 24). Antenna-plasma gap scans have been performed and find that for small gaps (5-8 cm), electron heating is observed with relatively small density rises and modest reductions in current penetration rate. For somewhat larger gaps (10-12 cm), weak electron heating is observed but with a spontaneous density rise at the plasma edge similar to that observed in NSTX H-modes. In the larger gap configuration, EFIT code reconstructions (without MSE [motional Stark effect]) find that resistive flux consumption is reduced as much as 30%, the internal inductance is maintained below 0.6 at 1 MA into the flattop, q(0) is increased significantly, and the MHD stability character of the discharges is strongly modified.