OptlCS Communications 91 (1992) 71-76 OPTICS North-Holland COM MUN ICATIONS An injector/amplifier double target configuration for the Ne-like Ge X-ray laser scheme C.L.S. Lewis, D. Neely, D.M. O'Neill, J.O. Uhomoibhi Department of Pure and Applied Phystcs, The Queen's Untversity of Belfast, Belfast, BT7 INN, N Ireland, UK M.H. Key Laser Dtvtston, Rutherford Appleton Laboratory, Chdton, Dldcot, Oxon OXI l OQX, England, UK Y. A1 Hadithi, G.J. Tallents Department of Physics, University of Essex, Colchester, C04 3SQ, England, UK and S.A. Ramsden l Department of Apphed Physics, Umverslty of Hull, Hull, HU6 7RX, England, UK Received 10 January 1992, revised manuscript received 25 March 1992 The XUV laslng output from one germanium slab target has been effictently coupled into, and further amphfied In, a second plasma produced by irradiation of a similar target from the opposite direction The operation of such a double target was shown to be strongly dependent on the distance by which the two target surfaces were displaced The hne brightness peaked for a surface displacement of ~ 200 gm and it was observed that the pointing direction of one output beam could be controlled by the surface separation in an asymmetric geometry Gain length products of ~ 16 with estimated output powers close to the megawan level were achieved on both the 23 2 and 23.6 nm J=2-1 transmons for an Optlmised target configuration Maximum effective cou- pling efficlencies of the individual outputs from double targets, comprising 2 2 and 1 4 cm length components, approached 100% for beams propagating from the shorter to the longer target 1. Introduction The first successful demonstration of a high gain- length product XUV laser system was based on elec- tron colhslonal processes in the Ne-llke 1on, Se XXV, and used ultra-thin selenium foils irradiated by 0.53 ~.I1TI laser light [ 1 ]. Since then, the collislonal exci- tation scheme has been further studied in several laboratories for a range of target designs and pump laser parameters [2-5 ]. Irradtauon of massive slab targets with 1.06 p_m light has been shown to provide a highly efficient method of gain production in Ne- Also at Department of Physics, University of York, YO1 5DD, England like Ge [6]. However, this design of target is subject to deleterious refraction effects which are expected to ulttmately limit the useful amphfier length as rays refract away from the high density, high gain plasma regions The double slab target configuration pre- sented here overcomes this limitation. In our par- tlcular case, due to geometric constramts, it has the added benefit of facihtatmg the operation of a long length (up to 4.4 cm) Ge amphfier using the total energy output of the six 110 mm dtameter beams on the VULCAN glass laser system at the UK SERC Central Laser Facility. Two separate targets are irradiated from opposite directmns. The ASE from one plasma may then cou- ple mto the second and further amplify as illustrated 0030-4018/92/$05 00 © 1992 Elsevier Science Publishers B V All rights reserved 71