Experiments on a MA-class Dense Plasma Focus (DPF) device have been carried out to investigate changes in neutron production by adding moderate amounts of krypton to a deuterium fill gas. The neutron yield from Z-pinch devices, including DPFs, conventionally scales as the peak current to the fourth power. However, a dramatic drop-off from ∼I4 scaling occurs above 3 MA, which recent modeling [D. T. Offermann et al., Phys. Rev. Lett. 116, 195001 (2016)] attributed to the transition in the predominant neutron production mechanism from beam-target fusion to thermonuclear fusion. Previously, the addition of Kr (and other high-Z) dopants has been shown to enhance beam-target fusion yields at currents below 300 kA, with optimal concentrations at 1%–2% Kr, whereas here we show that the optimal concentration of Kr at the MA level is near 0.1% by volume—elucidating a trend in the optimal Kr doping concentration as a function of the device scale. The neutron time-of-flight data reveal that Kr doping creates shorter and more intense neutron bursts, likely due a tighter but unstable pinch, highlighting a key trade-off for Kr doping.

中文翻译：

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氘中氪掺合物对兆安密集等离子体焦点中子产率的影响

已经在 MA 级密集等离子体聚焦 (DPF) 设备上进行了实验，以通过向氘填充气体中添加适量的氪来研究中子产生的变化。Z-pinch 器件（包括 DPF）的中子产额通常按峰值电流缩放到四次方。然而，从 ∼I4 缩放比例急剧下降发生在 3 MA 以上，最近的建模 [DT Offermann et al., Phys. 牧师莱特。116, 195001 (2016)] 归因于主要的中子产生机制从束靶聚变到热核聚变的转变。以前，添加 Kr（和其他高 Z）掺杂剂已被证明可以在低于 300 kA 的电流下提高束靶融合产率，最佳浓度为 1%–2% Kr，而在这里我们表明最佳浓度为MA 水平的 Kr 接近 0。1%（体积）——阐明了最佳 Kr 掺杂浓度随器件规模变化的趋势。中子飞行时间数据显示，Kr 掺杂会产生更短、更强烈的中子爆发，这可能是由于更紧但不稳定的夹点，突出了 Kr 掺杂的关键权衡。