Efficient Multi-Kev X-Ray Generation From High-Contrast Laser Plasma Interaction

K alpha line emission from Mo was experimentally and theoretically studied using clean, ultrahighintensity femtosecond laser pulses. The absolute yields of K alpha x-rays at 17 keV from Mo were measured as a function of the laser pulse contrast ratio and irradiation intensity. Significantly enhanced Icy yields were obtained by employing high contrast ratio at optimum irradiance. Conversion efficiencies of 4.28 x 10(-5)/sr, the highest values obtained to date, was demonstrated with contrast ratios in the range of 10(-10) to 10(-11).