Microparticle x-ray targets

The input power density of eroding rotating anode x-ray sources restricts the achievable spatial image resolution in x-ray systems, especially for medical computed tomography (CT). The development of anodes that sustain higher input power density has stalled in recent decades, despite substantial investment and sophisticated material analysis. The grain structure of the conversion layer, typically sintered and forged tungsten/rhenium, erodes during tens of millions of thermal cycles. Anodes of high-performance tubes are under extreme thermomechanical stress and rotate near angular burst velocities. To overcome this challenge, we propose a paradigm shift using a stream of very fast moving tungsten microparticles. Volume heating, twice the mass heat capacity and much shorter residence times under electron impact may render an order of magnitude improvement of the focal spot input power density. This corresponds to a threefold improvement of the source MTF in each orthogonal direction for a standard focal spot. We made sure by Monte-Carlo simulation, that the new microparticle target would not charge negatively upon electron impact in the tube voltage range of medical imaging. Hence, it would be electrically compatible with the spectral requirements. We propose technical implementations. We further suggest a source of high intensity and highly monochromatic bremsstrahlung based on microparticle technology that may replace synchrotrons for a variety of experiments. After thorough simulations we believe that the remaining engineering problems, such as separating the microparticle space from the cathode region, storage, acceleration, capturing, cooling, and recycling, can be solved in the near future.