Modelling of a nitrogen x-ray laser pumped by capillary discharge
Modelling of a nitrogen x-ray laser pumped by capillary discharge
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毛细管放电泵浦氮 X 射线激光器的建模
DOI：
10.2478/bf02475613
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发表时间：
2005
影响因子：
--
通讯作者：
P. Sasorov
中科院分区：
文献类型：
--
作者：
P. Vrba;M. Vrbova;N. Bobrova;P. Sasorov
我们进行了计算机模拟的快速放电中的氮气填充的氧化铝毛细管，以发现放电系统的参数，可能导致有效的复合泵浦的软X射线激光与活性介质所产生的H-类氮离子。用一维MHD程序计算了箍缩等离子体参量的时空依赖性。使用FLY代码作为后处理器，评估了所有电离状态和锂，氦和氢类氮离子的选定能级的种群的时间依赖性。发现N6+离子的粒子数反转发生在对应于Balmer α线的量子跃迁处，并计算了不同毛细管半径、初始压力、电流峰值和周期下的增益因子。对于毛细管半径1.5 mm、峰值电流50 kA、四分之一周期40 ns和填充气体压力0.5 kPa的优化布置，发现跨越1 ns时间间隔的增益因子为1 cm-1。需要指出的是，利用更薄的毛细管和更短的电流脉冲可以实现甚至更高的增益因子值，例如，如果毛细管半径为0.5mm，峰值电流为56 kA，四分之一周期为15 ns，并且填充氮气压力为3.9kPa，则实现6cm-1的增益因子。
We performed computer modelling of a fast electrical discharge in a nitrogen-filled alumina capillary in order to discover discharge system parameters that may lead to efficient recombination pumping of soft X-ray laser with active medium created by H-like nitrogen ions. The space-time dependences of pinch plasma quantities were found by means of a one-dimensional MHD code. Time dependences of populations of all ionisation states and populations of selected energy levels of lithium-, helium- and hydrogen-like nitrogen ions were evaluated using the FLY code as a post-processor. The population inversion was found at the quantum transition corresponding to the Balmer α-line of N6+ ions and the resulting gain factor was evaluated for different capillary radii, initial pressure, electric current peaks and periods. A gain factor of 1 cm−1 spanning the time interval of 1 ns was found for an optimised arrangement with capillary radius 1.5 mm, peak current 50 kA, quarter period 40 ns and filling gas pressure 0.5 kPa. It is pointed out that even higher values of the gain factor may be achieved with thinner capillaries and shorter current pulses, e.g. a gain factor of 6 cm−1 is achieved if the capillary radius is 0.5 mm, peak current 56 kA, quarter period 15 ns, and filling nitrogen pressure 3.9 kPa.