We report what is to our knowledge the first experimental study, of beam quality and prepulse effect tor a deeply saturated neonlike Zn soft-x-ray laser at 21.2 run, comparing two distinct regimes of operation: amplified spontaneous emission (in single pass) and double pass. The single-pass x-ray laser output emitted by a 30-mm-long plasma column delivers a smooth, highly symmetric ellipsoidal beam with horizontal and vertical divergence of 3(+/-0.5) and 5(+/-0.5) mrad, respectively. With a half-cavity consisting of a Mo:Si flat multilayer mirror, the x-ray laser output is boosted by factor of similar to11, providing a narrowly collimated beam with horizontal and vertical divergence of 3.8(+/-0.5) and 5.8(+/-0.5) mrad, respectively. The dependence of the beam parameters on the half-cavity setup and on the level of prepulse is described and discussed. (C) 2003 Optical Society of America. [References: 14]
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