复合X光激光中复合阶段拉氏点的特性

THE CHARACTERISTIC OF LAGRANGIAN CELLS IN EXPANDING RECOMBINATION PLASMA

给出了拉氏点在进入Ｎｅ／Ｔｅ增益目标区域后，其电子密度、电子温度、裸核布居概率、类Ｈ离子２—１线逃逸概率和增益随时间变化的近似估计式。

For an important Lagrangian cell with remarkable gain, there are two critical times:one is t c , at which the Langrangian cell changes from ionization into recombination; another is t g , at which the Lagrangian cell comes into N e/T e objective region of gain (ORG). In this paper, we gave approximate expressions of electron density N e , electron temperature T e ,fractional population of bare nuclei P 0 , the escape probability of 2-1 transition ρ e and gain g for 3d 5/2 -2p 3/2 transition in H-like C ions after t g in expanding plasma from a laser-irradiated carbon fibre. These approximate expressions are in agreement with numerical simulation. To have higher gain, the Lagrangian cell must enters into ORG with the characteristic values in the region, 0.1< T eg <0.3MK, P 0( t g)>0.6 , and ρ e>.07 ,where T eg is electron temperature at t g.t g must be shorter if T eg is lower. In plasma, the important region which gives gain is very narrow , N e is only 2 folds extension. If the pumping laser is a short pulse, t g must be shorter than 250ps. But t g can′t be too short because duration time of gain ～ t g . If the pumping laser is a long pulse, then half width of the pulse must be shorter than 100ps.