Advances in lower hybrid current drive technology on Alcator C-Mod

作者：Wallace G M^*; Shiraiwa S; Hillairet J; Preynas M; Beck W; Casey J A; Doody J; Faust I C; Fitzgerald E; Johnson D K; Kanojia A D; Koert P; Lau C; Lin Y; Leccacorvi R; MacGibbon P; Meneghini O; Murray R; Parker R R; Terry D R; Vieira R; Wilson J R; Wukitch S; Zhou L

来源：Nuclear Fusion, 2013, 53(7): 073012.

DOI：10.1088/0029-5515/53/7/073012

Lower hybrid current drive (LHCD) is an attractive option for non-inductive tokamak operation due to its high current drive efficiency and ability to drive current off axis. The parameters of the Alcator C-Mod LHCD system (f(0) = 4.6 GHz, B-phi similar or equal to 5.5T, (n) over bar (e) similar or equal to 10(20) m(-3)) are similar to the proposed LHCD system on ITER. This paper will describe improvements in LHCD technology on C-Mod designed to increase single-pass absorption at high (n) over bar (e), extend pulse length (to >3 s), and increase power delivered to the plasma (to similar to 2 MW). Modelling of lower hybrid (LH) wave propagation indicates that the observed loss of LHCD efficiency at higher (n) over bar (e) can be mitigated by enhancing the single pass power absorption through use of an off mid-plane launcher. The four rows of the launcher are located above the mid-plane (with I-P and B-phi both clockwise viewing from the top down) in order to exploit the poloidal upshift of n(parallel to) as rays propagate from the antenna into the plasma. The transmitter protection system (TPS) was redesigned to model the coolant temperature in real time and shut off the klystron beam voltage if the coolant is close to boiling. The TPS upgrade has been installed and operated on C-Mod for pulses up to 4.5 s into dummy loads and 1.0 s into the plasma. A new movable local LH launcher protection limiter was designed to reduce reflection coefficients across a wide range of launcher positions. Finally, a high power waveguide double-stub tuner is under development to provide feedback controlled load matching to reduce power reflected from the antenna under poor coupling conditions.

• 出版日期2013-7
• 单位中国地震局