Volume effect of laser produced plasma on X-ray emissions

An investigation of x-ray emission from Cu plasma produced by 1.054 mum Nd: glass laser pulses of 5 ns duration, at 2 x 10(12) -2 x 10(13) W cm(-2) is reported. The x-ray emission has been studied as a function of target posit ion with respect to the laser beam focus position. It has been observed tha t x-ray emissions from ns duration plasma show a volume effect similar to s ub-nanosecond plasmas. Due to this effect the x-ray yield increases when ta rget is moved away relative to the best focal plane of the laser beam. This result supports the theoretical model of Tallents and has also been testif ied independently using suitably modified theoretical model for our experim ental conditions. While above result is in good agreement with similar expe rimental results obtained for sub-nanosecond laser produced plasmas, it dif fers from result claiming filamentation rather than pure geometrical effect leading to x-ray enhancement for ns plasmas.