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Predictive modeling of a lithium vapor box divertor in NSTX-U using SOLPS-ITER
Nuclear Materials and Energy ( IF 2.3 ) Pub Date : 2021-04-17 , DOI: 10.1016/j.nme.2021.101004
E.D. Emdee , R.J. Goldston , J.D Lore , X. Zhang

The unmitigated heat flux in attached operation of a fusion power plant is predicted to be destructive to any solid divertor surface. Detachment, whereby the plasma pressure drops significantly before reaching the divertor target thus greatly reducing the heat flux and sputtering, will be necessary to ensure adequate lifetime of plasma facing components (PFCs). The lithium vapor box divertor aims to detach the divertor plasma via evaporating and condensing lithium surfaces. By evaporating lithium near or at the divertor plate and condensing it closer to the main chamber, a lithium vapor density gradient can be created. This density gradient ties energy losses to poloidal distance between the target and the detachment point. The radiation zone is then prevented from reaching the X-point as the lithium ionization rate decreases when the detachment front moves away from the divertor target. Here we present Scrape Off Layer Plasma Simulator (SOLPS) simulations of a lithium vapor box divertor using an NSTX-U equilibrium and PFC geometry. The parameters for the core boundary conditions, gas puff intensity, and heat and particle transport coefficients are chosen to match experimental values. Acceptable agreement with experimental Scrape-Off Layer (SOL) widths is found, indicating a reasonable choice of transport coefficients. In predictive simulations, lithium is added via evaporation at the target. Predictions for peak heat fluxes and upstream impurity concentration are given for a variety of evaporation rates. Target electron temperature is predicted to be able to be reduced to recombination levels (below 1 eV) for lithium evaporation rates of 11023 Li/s, indicating detachment. Peak heat flux at the lower outer target could be reduced by as much as a factor of six while maintaining upstream lithium fractions below 2%. The prevention of lithium from reaching the midplane is shown to be due to an increase in frictional forces acting on the lithium from a deuterium gas puff. Lithium is also shown to be redeposited close to the evaporator which is favorable for initial tests and future capillary porous systems.



中文翻译:

使用SOLPS-ITER对NSTX-U中的锂蒸气箱分流器进行预测建模

聚变电厂附属运行中的未减弱热通量预计将对任何固体偏滤器表面造成破坏。为了确保面向等离子体的组件(PFC)的寿命足够长,必须进行拆卸,以使等离子体压力在到达偏滤器目标之前显着下降,从而大大降低热通量和溅射。锂蒸气箱偏滤器旨在通过蒸发和冷凝锂表面来分离偏滤器等离子体。通过在分流板附近或在分流板上蒸发锂并使之靠近主腔室冷凝,可以产生锂蒸汽密度梯度。该密度梯度将能量损失与靶标与分离点之间的极向距离联系起来。当分离前沿从分流器目标移开时,当锂离子化速率降低时,可防止辐射区到达X点。在这里,我们介绍了使用NSTX-U平衡和PFC几何形状的锂蒸气箱分流器的刮除层等离子体模拟器(SOLPS)模拟。选择用于核心边界条件,吹气强度以及热量和颗粒传输系数的参数以匹配实验值。找到了与实验性可剥除层(SOL)宽度一致的可接受的协议,表明传输系数的合理选择。在预测模拟中,锂是通过蒸发在目标处添加的。给出了各种蒸发速率下的峰值热通量和上游杂质浓度的预测。1个1个023Li / s,表明脱离。在较低的外部靶材处的峰值热通量可以降低多达六分之一,同时将上游锂组分保持在2%以下。示出了防止锂到达中平面是由于增加了来自氘气团的作用在锂上的摩擦力。还显示锂在蒸发器附近重新沉积,这对于初始测试和将来的毛细管多孔系统非常有利。

更新日期:2021-04-28
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