Video Credit: NASA
Personal Note—I contributed to the design of the cryogenic temperature control system being used to cool the detector array in the Soft X-ray Spectrometer that will fly on Astro-H. The system is capable of holding the detector array at 0.05° above absolute zero with a stability better than ±0.000001°.
When an individual x-ray photon strikes one of the pixels in the SXS detector, the energy raises its temperature slightly which changes the resistance of the cell—the more energetic the photon, the greater the change. The low operating temperature and the tight regulation are necessary to make lower energy x-rays detectable and reduce system noise.