  An ultra-thin layer of uranium nitrides (UN) has been coated on the inner
surface of the depleted uranium hohlraum (DUH), which has been proved by our
experiment can prevent the oxidization of Uranium (U) effectively. Comparative
experiments between the novel depleted uranium hohlraum and pure golden (Au)
hohlraum are implemented on Shenguang III prototype laser facility. Under the
laser intensity of 6*10^14 W/cm2, we observe that, the hard x-ray (> 1.8 keV)
fraction of this uranium hohlraum decreases by 61% and the peak intensity of
total x-ray flux (0.1 keV ~ 5.0 keV) increases by 5%. Radiation hydrodynamic
code LARED is used to interpret the above observations. Our result for the
first time indicates the advantage of the UN-coated DUH in generating the
uniform x-ray field with a quasi Planckian spectrum and thus has important
implications in optimizing the ignition hohlraum design.
