Experimental investigation of beam heating in a soft X-ray scanning transmission X-ray microscope

A variable temperature sample holder with an operational range of 15 to 200 °C and an accuracy of ±1 °C has been fabricated for scanning transmission X-ray microscopes (STXM). Here we describe the device, and use it to image the polycrystalline morphology of solid stearic acid and palmitic acid at temperatures near their respective melting points as a means of checking for possible sample heating caused by the focused X-ray beam. The melting points observed in STXM were identical to those observed by conventional methods within measurement uncertainty, even under the most extreme, high dose rate imaging conditions investigated. The beam-induced temperature rise in the sample is inferred to be below 1 °C for dose rates of up to 2.7 GGy/s.