Narkis J, Conti F, Beg F N
Center for Energy Research, University of California San Diego, La Jolla, California 92093, USA.
Phys Rev E. 2022 Apr;105(4-2):045205. doi: 10.1103/PhysRevE.105.045205.
The gas-puff Z pinch has a long history with myriad applications as an efficient neutron or x-ray source. Its simplicity as a load configuration makes it suitable for studying fundamental plasma physics phenomena such as instabilities and energy transport. For example, the implosion of cylindrical shells onto a fusion fuel are inherently susceptible to instability growth on their external surfaces; if such instabilities are unmitigated, then the consequences in terms of degraded performance can be substantial. Similarly, mitigating heat transport from a hot fuel to its colder surrounding container can make fusion conditions more easily achievable. Here we have conducted a systematic study of triple-nozzle (outer liner, inner liner, fuel) gas puffs using two-dimensional (2D) magnetohydrodynamic simulations to investigate the effect of load material on the relevant dynamics. Analogous to past studies on spherical blast waves and converging shock waves, a trend emerges linking increased radiative cooling, lower adiabatic index, and increased magneto-Rayleigh-Taylor instability growth. Notably, our results suggest that, for the present configuration, Ar radiates less than both Ne and Kr during the early stages of the implosion while mass is being swept up and perturbations begin to seed instability growth. Consequently, pinches with Ar on the outer surface exhibit more stable 2D behavior. Here we also present a parameter scan of thermonuclear neutron yield, Y, as a function of peak current, I_{pk} and dopant concentration with Ne or Ar, depending on the inner liner material. Above 6 MA, our results suggest Y∝I_{pk}^{5} and even substantial mixing (10% by volume) of Ne into the fuel does not drastically reduce yield, suggesting an Ar/Ne/fuel configuration may reliably achieve DD thermonuclear yields of 10^{13}-10^{14}/cm in the 10-20 MA range.
喷气Z箍缩装置有着悠久的历史，作为一种高效的中子或X射线源有着无数的应用。其作为负载配置的简单性使其适用于研究诸如不稳定性和能量传输等基本等离子体物理现象。例如，圆柱形壳向内爆聚到聚变燃料上时，其外表面天生就容易出现不稳定性增长；如果这种不稳定性得不到缓解，那么性能下降方面的后果可能会很严重。同样，减轻从热燃料到其较冷的周围容器的热传输可以使聚变条件更容易实现。在这里，我们使用二维磁流体动力学模拟对三喷嘴（外层衬套、内层衬套、燃料）喷气进行了系统研究，以研究负载材料对相关动力学的影响。类似于过去对球面爆炸波和汇聚冲击波的研究，出现了一种趋势，将增加的辐射冷却、较低的绝热指数和增加的磁瑞利 - 泰勒不稳定性增长联系起来。值得注意的是，我们的结果表明，对于当前配置，在内爆的早期阶段，当质量被扫起且扰动开始引发不稳定性增长时，氩的辐射比氖和氪都少。因此，外表面有氩的箍缩表现出更稳定的二维行为。在这里，我们还给出了热核中子产额Y作为峰值电流Ipk以及根据内层衬套材料不同而添加的氖或氩掺杂浓度的函数的参数扫描结果。在6兆安以上，我们的结果表明Y∝Ipk5，并且即使将大量的氖（体积比10%）混入燃料中也不会大幅降低产额，这表明氩/氖/燃料配置在10 - 20兆安范围内可能可靠地实现1013 - 1014/厘米的氘 - 氘热核产额。
