Soft X-ray Laser by Hybrid Excitation Method Using Laser Produced Multiple Charged Ions

我提出了一种实现软X射线激光的新方法--混合激发法，高强度激光产生的多个带电离子在紧凑型放电装置的电功率作用下被进一步激发。由于Ar和高强度激光场的相互作用，我首次观察到了Ar_2^&lt；**&gt；的126 nm发射以及一些高次谐波信号。Ar准分子强度随聚焦激光强度的变化规律与隧道电离理论ADK理论所预测的一致。因此，我发现Ar准分子的产生是由高强度激光产生的电子引发的，它可能会取代电子束装置产生的电子。众所周知，隧道电离产生的电子温度对激光强度、波长和偏振非常敏感。然而，实验数据表明，当线性po…时，ar准分子的发射没有差别。更多的线化和圆偏振的激光光束与Ar相互作用。从理论上考虑强激光产生的等离子体中电子的能量输运，发现等离子体的快速传导冷却对准分子的产生起着重要的作用。为了模拟放电等离子体中的X射线辐射与稀有气体(Kr)的相互作用，利用激光产生等离子体的X射线源作为紧凑型X射线源。当激光等离子体的软X射线发射激发Kr原子时，观察到147 nm处的Kr准分子发射和157 nm处的Kr~(2+)发射。这些发射的时间分辨数据都显示出与等离子体引发激光一样快的上升倍，表明等离子体软X射线发射直接产生离子/准分子。这可能是有利的，因为准分子的产生不会受到电子去激发过程的太大影响。根据光致电离模型，Kr~(2+)~(2+)&Gt~(2+)离子是由Kr~4P电子的光致电离产生的。这种离子产生通过离子通道启动了准分子的产生动力学。较少

I have proposed a hybrid excitation method as a new method to realize a soft x-ray laser where high intensity laser produced multiple charged ions are further excited by electrical power from a compact discharge device.As a result of the interaction of Ar and high intensity laser field, I have observed emission from Ar_2^<**> at 126 nm for the first time together with some signals of high order harmonics. The focused laser intensity dependence of the Ar excimer intensity agrees well with that predicted by a tunnel ionization theory so called ADK theory. I,therefore, found out that the production of Ar excimers was initiated by high intensity laser produced electrons, which may become a substitution to those produced by an electron beam device.It is well known that the electron temperature as a result of tunnel ionization is very sensitive to laser intensity, wavelength, and polarization. Experimental data, however, show no difference in terms of the Ar excimer emission when linearly po … More larized and circularly polarized laser beams interacted with Ar. Considering about the energy transport of electrons in a high intensity laser produced plasma theoretically, I have found out a rapid conductive cooling of a plasma plays an important role for the excimer production. A cooling time constant for the appropriate excimer production is much faster than the three body recombination time constant which is a main production process of the excimers.In order to simulate an interaction between x-ray emission from a discharge plasma and rare gas (Kr), an x-ray source using laser produced plasma was used as a compact x-ray source. When Kr atoms were excited by soft x-ray emission from a laser produced plasma, Kr excimer emission centered at 147 nm was observed as well as emission from Kr^<2+> at 157nm.Time resolved data of these emissions show both rise times as fast as that of a plasma initiating laser, indicating the direct ion/excimer production by soft x-ray emission from a plasma. This may be advantageous because the excimer production is not much affected by an electron deexcitation process. Based on a photoionization model, the Kr^<2+> ions are produced by photoionization of Kr 4p electrons. This ion production initiates the excimer production kinetics by ionic channels. Less