通过数值求解等离子体流体力学方程组,研究了短脉冲激光打靶结束后形成的短密度梯度尺度等离子体的冷却降温过程,讨论了热传导、膨胀作功、辐射损失三种冷却机制对降温过程的贡献,并用解流体力学方程组得到的等离子参数计算了MgXI等离子体中波长小于20 nm的所有可能跃迁的自发辐射放大增益系数,分析了它们与环境条件的关系,指出了在MgXI等离子体中获取水窗附近乃至水窗波段软X射线激光的可能性。

In this paper,the cooling process of a short scale-length plasma after the short driving laser pulse termination is studied by solving the hydrodynamic equations of a plasma with numical calculation.The contributions of heat conduct,work done by expanding and energy loss by radiation are discussed.Then gain coefficients of several possible transitions for wavelength less 20 nm in MgXI plasmas are calculated with the plasma parameters obtained from the solution of hydrodynamic equations. The influences of environment to them are analysed. The possibility of producing a soft X-ray laser near by water-window in MgXI plasmas is predicated.