[en] We are studying the feasibility of utilizing Kα x-ray sources in the range of 20 to 100 keV as a backlighters for imaging various stages of implosions and high areal density planar samples driven by the NIF laser facility. The hard x-ray Kα sources are created by relativistic electron plasma interactions in the target material after a radiation by short pulse high intensity lasers. In order to understand Kα source characteristics such as production efficiency and brightness as a function of laser parameters, we have performed experiments using the 10 J, 100 fs JanUSP laser. We utilized single-photon counting spectroscopy and x-ray imaging diagnostics to characterize the Kα source. We find that the Kα conversion efficiency from the laser energy is ∼ 3 x 10^-4