A long duration high fluence x-ray source has been developed at the National Ignition Facility (NIF). The target was a 14.4mm tall, 4.1mm diameter, epoxy walled, gas filled pipe. Approximately 1.34MJ from the NIF laser was used to heat the mixture of (55:45) Kr:Xe at 1.2 atm (~5.59mg/cm³) to emit in a fairly isotropic radiant intensity of 400-600GW/sr from the Ephoton 3-7 keV spectral range for a duration of ≈ 14 ns. The HYDRA simulated radiant intensities were in reasonable agreement with experiments but deviated at late times. [ABSTRACT FROM AUTHOR]