Spherical tokamaks (STs) have features that make them a potentially attractive option for fusion power production compared to conventional tokamaks (CTs) including operation at high beta and high self-driven ‘bootstrap’ current. The thermal energy confinement time (τ _Ε) also typically has a stronger dependence on toroidal magnetic field and a weaker dependence on plasma current, but so far it has not been established how this difference impacts performance under reactor conditions. This aspect is explored in this paper. Using empirical data from NSTX and MAST, and from multiple CTs, we investigate analytically and by using established fusion codes the potential fusion performance, characterised by the fusion triple product, nTτ _Ε, and fusion power gain, Q _fus, where n and T are the density and temperature respectively. We find that for similar values of field and fusion power, but smaller volume, STs can have nTτ _Ε up to a factor of three higher and Q _fus an order of magnitude higher than CTs. We identify the origin of this enhanced performance and outline a measurement to advance this finding. Potentially our results open an alternative and faster route to fusion power based on relatively small, low power STs.

与传统的托卡马克（CT）相比，球形托卡马克（ST）具有使其成为融合动力生产的潜在吸引力的功能，包括在高beta和高自驱动“自举”电流下运行。热能量约束时间（τ _Ε）还通常具有上环形磁场更强的依赖和在等离子体电流较弱依赖性，但到目前为止，还没有建立如何反应器条件下这种差异会影响性能。本文将探讨这一方面。使用从NSTX和肥大的经验数据，以及来自多个电流互感器，我们调查分析，并通过建立融合码的潜在融合性能，特点是融合三重积，nTτ _Ε，融合功率增益，Q _fus，其中n和T分别是密度和温度。我们发现，现场和融合力，但体积较小的类似值，STS可以有nTτ _Ε最多的一个因素三高和Q _FUS一个数量级高于CT的。我们确定了这种增强性能的根源，并概述了一项测量方法以推进这一发现。潜在地，我们的结果为基于相对较小的低功率ST的融合功率开辟了一条替代途径，并且是一条更快的途径。