Numerical modeling of a high-gain x-ray laser in an avalanche recombination high density plasma

雪崩复合高密度等离子体中高增益 X 射线激光器的数值模拟

基本信息

批准号：
15540478
负责人：
ODA Toshiatsu
金额：
$ 1.28万
依托单位：
HIROSHIMA KAKUSAI GAKUIN UNIVERSITY
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
2003
资助国家：
日本
起止时间：
2003 至 2004
项目状态：
已结题

项目摘要

The recombination x-ray laser has been extensively studied because this scheme has potentiality to develop compact x-ray laser. However, most investigations have been made in plasmas under the quasi-steady state approximation. In these plasmas, the population inversion cannot be generated for higher electron density than a certain value. Consequently, the gain for laser oscillation cannot be increased over a limited value. The objective of our project by numerical calculation is to demonstrate that significant improvement in gain performance becomes feasible of the recombination x-ray laser in quite transient (avalanche) recombination of high density plasma in which the quasi-steady state approximation is invalid. An outline of our research results is as follows :An atomic physics code is developed for the avalanche recombination plasma with low-z ions. Time-dependent rate equations for carbon ions were solved in the recombination phase of the fully ionized carbon high density plasma. The initial electron temperature was set to be 10 eV, equivalent to 0.28 eV for the hydrogen plasma. For the electron density higher than 10^<19>cm^<-3> the gain for the C Vl 18.2 nm becomes over 5000cm^<-1>, and increases with the electron density while the duration of population inversion decreases from 1 ps to 10 fs. This shows transient high-gain x-ray laser is feasible due to the avalanche recombination. Charge exchange process between fully ionized carbon ions and helium atoms was also included in the rate equations. The calculation shows that the gain for the CVl 18.2 nm line is as much as 3500cm^<-1> while the corresponding gain without the charge exchange process decreases down to about 200cm^<-1>. This clearly indicates that the charge exchange process plays also a very useful role in producing the avalanche recombination x-ray laser.

复合X射线激光器已被广泛研究，因为该方案具有开发紧凑型X射线激光器的潜力。然而，大多数研究都是在准稳态近似下的等离子体中进行的。在这些等离子体中，当电子密度高于某个值时，无法产生粒子数反转。因此，激光振荡的增益不能增加到超过有限值。我们的项目通过数值计算的目的是证明在准稳态近似无效的高密度等离子体的相当瞬态（雪崩）复合中，复合X射线激光器的增益性能的显着改善是可行的。我们的研究成果概要如下：开发了低z离子雪崩复合等离子体的原子物理代码。在完全电离碳高密度等离子体的复合阶段求解了碳离子的时间相关速率方程。初始电子温度设置为 10 eV，相当于氢等离子体的 0.28 eV。对于高于10^<19>cm^<-3>的电子密度，C VI 18.2 nm的增益变得超过5000cm^<-1>，并且随着电子密度的增加而增加，而粒子数反转的持续时间从1 ps减少至 10 fs。这表明由于雪崩复合，瞬态高增益 X 射线激光是可行的。完全电离的碳离子和氦原子之间的电荷交换过程也包含在速率方程中。计算表明CV1 18.2 nm线的增益高达3500cm ^ -1 ，而没有电荷交换过程的相应增益下降至约200cm ^ -1 。这清楚地表明电荷交换过程在产生雪崩复合 X 射线激光中也发挥着非常有用的作用。