Liquid metal anode X-ray tubes and their potential for high continuous power operation

A novel type of electron-impact X-ray source is described in which X-rays are produced in a turbulently flowing liquid metal that is separated from the vacuum region of the X-ray source by a thin membrane. Following a summary of the physics of electron and photon transport applicable to the liquid metal anode X-ray (LIMAX), the three diffusion processes responsible for thermal transport in (electron diffusion, heat conduction and turbulent mixing) are briefly discussed and their relative importance is quantitatively assessed. A simple Gaussian model is presented allowing the characteristic ranges of the three diffusion processes to be combined into a mean total diffusion range. The extent to which heat diffuses in the time taken for the liquid metal stream to pass the electron focus permits the loadability (electron beam power density per unit maximum anode temperature rise) of the turbulently flowing liquid metal target to be assessed. A description of an experimental LIMAX facility constructed in these laboratories is given. Preliminary experimental results from the LIMAX facility are presented and satisfactory agreement is found between these results and the predictions of the Gaussian model for the mean total diffusion range. The suitability of the LIMAX proposal for X-ray scatter imaging investigations is briefly considered. (C) 2003 Elsevier Science Ltd. All rights reserved.