Abstract: An x-ray generator including a light source; a high temperature photocathode arranged so as to be illuminated by light from the light source; an accelerator for accelerating electrons emitted by the photocathode; and a target onto which accelerated electrons impinge so as to produce x-rays, the target being held at substantially ground potential. The accelerator is arranged so that the photocathode is at a low voltage end of a voltage multiplier, typically held at about -100 kV, and the target is at the high voltage end at ground potential. The voltage multiplier can include a bank of nested tubular capacitor members which surround the photocathode and accelerator section and are arranged such that the outer surface is at ground potential, the same as the target.