Long pulse enhanced confinement discharges in the HT-7 superconducting tokamak by ion Bernstein wave heating and lower hybrid wave current drive

摘要

Significant progress has been made on the HT-7 superconducting tokamak (R=1.22 m, a=0.27 m) in the past year toward obtaining advanced operating modes in steady state. By combining ion Bernstein wave and lower hybrid current drive edge-localized-mode-free limiter H-mode discharges with H(89)similar to2, beta(N)(*)H(89)>3 have been obtained that lasted for 53 tau(E). A well-boronized wall prevented further impurity accumulation and the large pumping kept the recycling at a very low level. The density was kept almost constant with the feedback control. The noninductive driven current fraction is about 60% and bootstrap fraction is about 18%. The central electron temperature is about 2.6 keV and density above 2x10(19) m(-3). With reduced plasma parameters of central Tesimilar to1.5 keV and n(e0)similar to2x10(19) m(-3), H(89)similar to1.45, beta(N)similar to1.1, the improved confinement phase lasts for more than 100 tau(E) with the noninductive driven current fraction similar to70%. (C) 2003 American Institute of Physics. [References: 20]