An x-ray source includes an insulating tube having a cylindrical inside surface defining a cylindrical vacuum cavity, a cathode located near a first end of the insulating tube and adapted to be optically heated for emitting electrons, an anode adapted for a voltage bias with respect to the cathode for accelerating electrons emitted from the cathode, an x-ray emitter target located near a second end of the insulating tube for impact by accelerated electrons, and a secondary emission reduction layer covering at least a portion of the inside surface and adapted to minimize charge build-up on the inside surface, wherein the insulating tube is adapted to be weakly conductive to support a uniform voltage gradient along the insulating tube and across the voltage bias between the cathode and the anode.