Effects of long rarefied plasma on fast electron generation for FIREX-I targets
Effects of long rarefied plasma on fast electron generation for FIREX-I targets
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DOI：
10.1017/s0263034611000735
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发表时间：
2012-04
影响因子：
0.9
通讯作者：
H. Sakagami;A. Sunahara;T. Johzaki;H. Nagatomo
中科院分区：
文献类型：
--
作者：
H. Sakagami;A. Sunahara;T. Johzaki;H. Nagatomo
在锥导快速点火方案中，加热激光的预脉冲在锥体内部产生大尺度的预制等离子体，发现预制等离子体大大降低了加热激光与特别适合于堆芯加热的快电子的耦合效率。为了缓解这个严重的问题，建议在圆锥体的入口处覆盖一层极薄的薄膜。然而，这种方法在圆锥体入口处引入了长的稀薄等离子体，主脉冲必须通过这些等离子体传播。因此，主脉冲产生的快电子特性可能会受到影响，并研究了长稀薄等离子体对快电子产生的影响。结果表明，与没有稀薄等离子体时相比，电子束强度变大，但由于没有合适的电子用于堆芯加热，加热激光与堆芯之间的能量耦合率降低。为了获得小于10%的核心电子温度退化，必须对薄膜进行预脉冲辐照以使稀薄等离子体的长度和密度小于500μm和临界密度的十分之一。薄膜的厚度可以通过这些标准和预脉冲的强度来确定。
Long-scale preformed plasmas are generated inside the cone by the pre-pulse of the heating laser in the cone-guided fast ignition scheme and it is found that coupling efficiency from the heating laser to fast electrons especially suitable for core heating is drastically reduced by the preformed plasmas. To mitigate this serious problem, an extremely thin film is suggested to cover the entrance of the cone. This method, however, introduces long rarefied plasmas around the entrance of the cone and the main pulse must propagate through these plasmas. Therefore, fast electron characteristics produced by the main pulse could be affected, and effects of long rarefied plasmas on fast electron generation are investigated. It is found that the electron beam intensity becomes larger than that without the rarefied plasma, but the energy coupling rate from the heating laser to the core decreases due to lack of appropriate electrons for core heating. To achieve less than 10% degradation of the core electron temperature, the thin film must be expanded by irradiation of the pre-pulse so that the length and the density of rarefied plasmas become less than 500 μm and one-tenth of the critical density. A thickness of the thin film can be determined by these criteria and the intensity of the pre-pulse.