  A three dimensional molecular dynamic code is used to study the generation of
fusion neutrons from Coulomb explosion of Deuterium clusters driven by intense
near infra-red (NIR) laser ($\lambda=800nm$) of femtosecond pulse duration
($\tau=50 fs$) under beam-target interaction scheme. We have considered various
clusters of average sizes ($\langle R_0\rangle$=80,140,200\AA) which are
irradiated by a laser of peak spatial-temporal intensity of 1$\times10^{18}
W/cm^{2}$. The effects of cluster size and spatial laser intensity distribution
on ion energies due to the Coulomb explosion of the cluster are included by
convolution of single cluster single intensity ion energy distribution function
(IEDF) over a range of cluster sizes and laser intensities. The final
convoluted IEDF gets broadened on both lower and higher energy sides due to
this procedure. Furthermore, the neutron yield which takes into account the
convoluted IEDF, also gets modified by a factor of $\sim$2 compared to the case
when convolution effects are ignored.
