Soft x-ray emissions from laser plasma of cryogenic mixture targets

Soft x-ray spectral radiation from Xe-CO2 mixture cryogenic targets with a Xe mole fraction of 0% (pure CO2) to 100% (pure Xe) irradiated by a 1 mu m pulse laser at a laser intensity I-L of 0.3-1.0x10(12) W/cm(2) has been obs erved. The x-ray conversion efficiency per Xe mole fraction was found to ha ve maximum values at the Xe fractions of 10% for I-L=6.0x10(11) W/cm(2) and 5% for I-L=1.2x10(12) W/cm(2), which were about five and ten times as larg e as that in a pure Xe target, respectively. The x-ray conversion efficienc ies in the cryogenic mixture targets at Xe fractions of 10%-40% were about 1.3 %/sr/nm for lambda=10.8 nm and I-L=10(12) W/cm(2), which was as high as that in a pure Xe cryogenic target. The physical mechanism behind this enh anced emission is discussed. (C) 1999 American Institute of Physics. [S0003 -6951(99)03540-8].