1 EX / P 6-26 Current profile control studies on MAST
1 EX / P 6-26 Current profile control studies on MAST
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1 EX / P 6-26 当前 MAST 调剖研究
DOI：
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发表时间：
2008
期刊：
影响因子：
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通讯作者：
S. Pinches
中科院分区：
文献类型：
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作者：
M. Turnyanskiy;D. Keeling;R. Akers;G. Cunningham;H. Meyer;S. Pinches
MAST 实验 [1] 和拟议的 MAST 升级的主要操作目标之一是研究控制 q 分布和驱动离轴电流的可能机制。进行实验以确定使用两种不同方法（瞬态和稳态）可以修改 q 分布的程度。研究了等离子体电流上升阶段期间的瞬态效应，目的是开发一种启动机制，该启动机制随后可用作非感应电流驱动的目标等离子体或访问高级操作模式，例如混合或改进的 H 模式。在这种情况下，当早期中性束注入（NBI）应用于快速电流斜坡率启动等离子体时，观察到最显着的效果，导致反向磁剪切和等离子体电流“堆积”离轴。在研究离轴 NBI 的稳态实验中，结果表明，通过注入离轴中性束 (NB) 来拓宽快速离子沉积剖面有助于避免有害的等离子体不稳定性，并显着扩展 MAS T 的操作窗口。长脉冲 (>0.65s) H 模式等离子体的实现仅受当前机器和 NBI 工程限制的等离子体持续时间的限制。为了匹配实验观察到的中子速率和储存能量，需要低水平的反常快离子扩散（D b~0.5ms）。快离子扩散的引入拓宽了中性束电流驱动 (NBCD) 轮廓，并将 NB 驱动电流的相对贡献从约 40% 降低到约 30%。为了获得电流分布的直接测量结果，多弦 MSE 诊断已在 MAST 上调试，目前正在提供第一批结果，以确认 NB 驱动电流的 f 轴位置。
One of the main operational aims of the MAST experi m nt [1] and the proposed MAST upgrade is to invest igate possible mechanisms to control the q-profile and dr ive off-axis current. Experiments were carried out to determine the extent to which the q-profile may be modified using two different approaches, transient and steadystate. Transient effects during the plasma current ramp-up phase were investigated with the aim of dev eloping a start-up regime that can later be used as a target plasma for non-inductive current drive or to access advanced modes of operation such as the hybrid or improved H -mode. The most significant effect in this case was ob erved when early Neutral Beam Injection (NBI) was applied to the fast current ramp-rate start up plasmas cau ing reversed magnetic shear and the plasma current to ‘ pile-up’ off-axis. In steady-state experiments, in which off-axis NBI was studied, results indicate that broadening the f ast ion deposition profile by off axis neutral beam (NB) in jection helps to avoid harmful plasma instabilities and significantly extends the operational window of MAS T. Long pulse (>0.65s) H-mode plasmas were achieved with plasma duration limited only by present machin e and NBI engineering limits. In order to match the experimentally observed neutron rate and stored ene rgy a low level of anomalous fast ion diffusion (D b~0.5m s) is required. The introduction of the fast ion diffu sion broadens the Neutral Beam Current Drive (NBCD) profile and degrades the relative contribution of NB driven current from ~40% to ~30%. To obtain direct measur ements of the current profile, a multi-chord MSE diagnosti c has been commissioned on MAST and is currently delivering first results in order to confirm the of f axis location of the NB driven current.