Electron backscatter in X-ray tubes: experiment and analysis

X-ray medical imaging techniques use 80-140 kV X-ray tubes running at increasingly high power levels (52 kW instantaneous) to generate high quality images with low exposure times. X-rays are generated at <1% efficiency in the anode, with the balance of the input power converted to heat. In addition to radiative and conduction heat transport, it is necessary to explicitly consider electron backscatter (EBS) as an independent heat transfer mechanism for design of the highest power X-ray tubes. Here we discuss EBS physics and X-ray tube aspects, describe experimental measurement of spatially resolved EBS current in a high power demountable X-ray tube system and obtain a good comparison with numerical analysis of EBS current distribution.