X-RAY LASING IN COLLIDING PLASMAS

Conditions favorable for the achievement of population inversion and l arge gains in short-pulse laser-heated selenium have been reported on previously [K. G. Whitney et al., Phys. Rev. E 50, 468 (1994)]. Howeve r, the required density profiles to minimize refraction and amplificat ion losses can be difficult to achieve in conventional laser heated bl owoff plasmas. The feasibility of accelerating plasma with a laser, an d letting it collide with a solid density wall plasma has been explore d. The density of the resulting shocked plasma can be controlled and r efraction can be reduced in this design. A radiation hydrodynamics mod el is used to simulate the collision of the laser produced selenium pl asma with the wall plasma. The heating of the stagnated plasma with a short-pulse laser is then simulated, providing the hydrodynamic respon se of the selenium plasma and detailed configuration nonequilibrium at omic populations. From the results of these calculations, it appears f easible to create an x-ray lasing selenium plasma with gains in the J = 0 - 1 line at 182 Angstrom in excess of 100 cm(-1).