INTERFEROGRAMS OBTAINED WITH A X-RAY LASER BY MEANS OF A WAVE-FRONT DIVISION INTERFEROMETER

A wavefront division interferometer has been used for the first time w ith a soft X-ray laser (lambda = 21.2 nm). The experiment aims to demo nstrate X-ray laser interferometry in this configuration and to invest igate the phase shifting measurement accuracy as well. The X-ray laser is generated in a neon-like zinc plasma in which it makes two passes thanks to a multilayer min- or half-cavity. The X-ray pulse duration i s approximate to 50 ps. The beam has a very high brightness (approxima te to 4 x 10(15) W cm(-2) sr(-1) in 0.01% bandwidth) which allows us t o place the interferometer far from the source (2.8 m) and thus to ben efit by a large transverse coherence width. The interferometer consist s of a Fresnel bi-mirror which odds coherently one part of the X-ray l aser beam section to the other one. Single laser-shot interferograms o f a reflecting sample provided with a lambda/2 dephasing step (51.7 nm height) have then been successfully recorded. The phase shifting accu racy resulting from the smallest observable fringe change is about lam bda/20. (C) 1997 Elsevier Science B.V.