A spatially modulated copper target surface (groove diameter (lambda) s approximately equals 70 plus or minus 2 micrometer and groove depth dS equals 20 plus or minus 2 micrometer shows an enhanced X-ray fluence and wider angle of emission as compared to optically polished ((lambda) /2), planar copper target when irradiated with laser energy density EL approximately equals 600 J/cm2. Experiments were performed using a 40 ps (FWHM), 1.06 micrometer laser. An array of 5 X-ray detectors at various angle to the laser axis measured the angular distribution of X-ray fluence. Higher X- ray flux and wider angle of emission are attributed to invoking of resonance absorption at the curvature, shape of curvature of the spatially modulated surface groove respectively. In this article we address to the issues of large angle emission of X-rays, their magnitude and scaling laws for both types of targets. Since X-ray emission time depends on laser pulse duration, present experimental results are discussed explicitly on the laser energy density dependance (J/cm2).
|