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

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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