The mission of the spherical tokamak NSTX-U is to explore the physics that drives core and pedestal transport and stability at high- and low collisionality, as part of the development of the spherical tokamak (ST) concept towards a compact, low-cost ST-based pilot plant. NSTX-U will ultimately operate at up to 2 MA and 1 T with up to 12 MW of neutral beam injection power for 5 s. NSTX-U will operate in a regime where electromagnetic instabilities are expected to dominate transport, and beam-heated NSTX-U plasmas will explore a portion of energetic particle parameter space that is relevant for both -heated conventional and low aspect ratio burning plasmas. NSTX-U will also develop the physics understanding and control tools to ramp-up and sustain high performance plasmas in a fully-noninductive fashion. NSTX-U began research operations in 2016, but a failure of a divertor magnetic field coil after ten weeks of operation resulted in the suspension of operations and initiation of recovery activities. During this period, there has been considerable work in the area of analysis, theory and modeling of data from both NSTX and NSTX-U, with a goal of understanding the underlying physics to develop predictive models that can be used for high-confidence projections for both ST and higher aspect ratio regimes. These studies have addressed issues in thermal plasma transport, macrostability, energetic particlet-driven instabilities at ion-cyclotron frequencies and below, and edge and divertor physics.
球形托卡马克NSTX-U的使命是探索在高和低碰撞率下驱动芯部和台基输运及稳定性的物理，作为球形托卡马克（ST）概念向紧凑、低成本的基于ST的实验堆发展的组成部分。NSTX-U最终将在高达2 MA和1 T的条件下运行，并具有高达12 MW的中性束注入功率，持续5秒。NSTX-U将在电磁不稳定性预计主导输运的 regimes 中运行，且束加热的NSTX-U等离子体将探索与常规和低纵横比燃烧等离子体相关的能量粒子参数空间的一部分。NSTX-U还将发展物理理解和控制工具，以在全非感应方式下建立和维持高性能等离子体。NSTX-U于2016年开始研究运行，但在运行十周后偏滤器磁场线圈发生故障，导致运行暂停并启动恢复活动。在此期间，在分析、理论和建模方面开展了大量工作，涉及NSTX和NSTX-U的数据，目标是理解基本物理，以开发可用于高置信度预测常规和更高纵横比 regimes 的模型。这些研究涉及热等离子体输运、宏观稳定性、离子回旋频率及以下的能量粒子驱动不稳定性，以及边界和偏滤器物理等问题。