Krypton as stopper for ions and small debris in laser plasma sources

A preliminary theoretical and experimental demonstration of the successful use of krypton as stopper for ions and small debris (Phi < 1 <mu>m) in lase r plasma sources is discussed. In particular, for applications to projectio n micro-lithography at h nu = 60-90 eV, an ions rejection by almost 2 order s of magnitude is obtained at a Kr pressure compatible for more than 80% tr ansmission of the EUV radiation.