Patent ID: 7236568

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