X-RAY LASER-BEAM PROPAGATION IN DOUBLE-FOIL TARGETS

Refraction effects on the gain of an x-ray laser propagating in a convex (lateral) plasma density profile have been studied previously. Here the corresponding case of concave density profile is studied theoretically. Experimentally, the convex profile is obtained by irradiating a single (exploding) foil target; the concave case can be realized by various two-beam irradiation configurations. Such geometries have been studied experimentally at the Laboratory for Laser Energetics (LLE) [SPIE Proceedings (SPIE, Bellingham, WA, 1987), Vol. 831, Paper 40, p. 283; Paper 42, p. 305]. The concave profile has a waveguiding effect on the propagation of the x-ray laser and can reduce the deleterious effects of refraction. The output power, its dependence on the length of the amplifying medium, and its angular distribution are studied and compared with the convex profile case. An amplifier mode (in which a collimated beam is incident on an amplifying medium) is compared with an amplified spontaneous emission mode (where spontaneous emission sources exist throughout the amplifying medium). © 1990 American Institute of Physics.