Nanophotonic Thermal Management in X-ray Tubes.

Abstract

In X-ray tubes, more than 99% of the kilowatts of power supplied to generate X-rays via bremsstrahlung is lost as heat in the anode. Therefore, thermal management is a critical barrier to the development of more powerful X-ray tubes with higher brightness and spatial coherence, which are needed to translate imaging modalities such as phase-contrast imaging to the clinic. In rotating anode X-ray tubes, the most common design, thermal radiation is a bottleneck that prevents efficient cooling of the anode─the hottest part of the device by far. We predict that nanophotonic patterning of the anode of an X-ray tube enhances heat dissipation via thermal radiation, enabling it to operate at higher powers without an increase in temperature. The focal spot size, which is related to the spatial coherence of generated X-rays, can also be reduced at a constant temperature. A major advantage of our "nanophotonic thermal management" approach is that in principle, it allows complete control over the spectrum and direction of thermal radiation, which can lead to optimal thermal routing and improved performance.