Requirements on localized current drive for the suppression of neoclassical tearing modes
Requirements on localized current drive for the suppression of neoclassical tearing modes
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DOI：
10.1088/0029-5515/51/10/103007
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发表时间：
2011-10
期刊：
影响因子：
3.3
通讯作者：
N. Bertelli;D. Lazzari;E. Westerhof
中科院分区：
文献类型：
--
作者：
N. Bertelli;D. Lazzari;E. Westerhof
完全抑制 NTM 的启发式标准被表述为 ηNTM == jCD,max/jBS ⩾ 1.2 (Zohm et al 2005 J. Phys. Conf. Ser. 25 234)，其中 jCD,max 是用于稳定模式的驱动电流密度分布中的最大值，jBS 是局部自举电流密度。在这项工作中，我们在广义卢瑟福方程的基础上对该准则进行了系统的理论分析。仅考虑岛内 jCD 的影响，通过最小施加总电流进行完全抑制的新标准以驱动电流宽度 wdep 的最大允许值的形式获得，并结合 wdepηNTM 形式的总驱动电流所需的最小值，其中两个限制都取决于边缘和饱和岛尺寸。当考虑到额外的影响时，例如稳定参数 Δ' 与岛外驱动电流的变化、功率调制、岛内伴随的加热或当先发制人地应用电流驱动时，这些要求可以放宽。当应用于 ITER 场景 2 时，完全抑制 3/2 或 2/1 NTM 的要求变为 wdep ≲ 5 cm 和 wdepηNTM ≳ 5 cm，与（Sauter 等人 2010 Plasma Phys. Control. Fusion 52 025002）一致。为了实现完全 NTM 抑制所需的最小功率，优化 ITER ECRH 上端口发射器设计需要将下转向镜的环形注入角比其当前设计值增加几度，而对于上转向镜，当前设计值接近最佳值。
A heuristic criterion for the full suppression of an NTM was formulated as ηNTM ≡ jCD,max/jBS ⩾ 1.2 (Zohm et al 2005 J. Phys. Conf. Ser. 25 234), where jCD,max is the maximum in the driven current density profile applied to stabilize the mode and jBS is the local bootstrap current density. In this work we subject this criterion to a systematic theoretical analysis on the basis of the generalized Rutherford equation. Taking into account only the effect of jCD inside the island, a new criterion for full suppression by a minimum applied total current is obtained in the form of a maximum allowed value for the width of the driven current, wdep, combined with a required minimum for the total driven current in the form of wdepηNTM, where both limits depend on the marginal and saturated island sizes. These requirements can be relaxed when additional effects are taken into account, such as a change in the stability parameter Δ′ from the current driven outside the island, power modulation, the accompanying heating inside the island or when the current drive is applied preemptively. When applied to ITER scenario 2, the requirement for full suppression of either the 3/2 or 2/1 NTM becomes wdep ≲ 5 cm and wdepηNTM ≳ 5 cm in agreement with (Sauter et al 2010 Plasma Phys. Control. Fusion 52 025002). Optimization of the ITER ECRH Upper Port Launcher design towards minimum required power for full NTM suppression requires an increase in the toroidal injection angle of the lower steering mirror of several degrees compared with its present design value, while for the upper steering mirror the present design value is close to the optimum.