Prospects of "water-window" X-ray emission from subpicosecond laser plasmas

Soft-X-radiation in the "water-window" region (23.3-43.6 Angstrom) mainly f rom carbon laser plasmas generated by subpicosecond (700 fs) 0.248-mu m las er pulses is studied as a function of angle of incidence and intensity (up to 10(18) W/cm(2)) for p-polarized laser light. Furthermore, com parison is made between plasmas generated from massive and foil targets. Numerical ca lculations are performed using a hydrocode coupled to X-ray line and contin uum emission calculations including radiation transport. The optimized cond itions to achieve maximum water-window X-ray emissivity and, in particular, carbon Lyman-alpha line emission are investigated. In addition, analytical scalings are presented. These theoretical results are essentially confirme d by previous experiments. It is found that at optimized conditions, picose cond or subpicosecond laser plasma X-ray sources with a power of the order of 1-10 GW in a spectral window of 1 Angstrom could be developed.