Transition-Edge Sensors for cryogenic X-ray imaging spectrometers

Large arrays of superconducting transition-edge sensor (TES) microcalorimeters are becoming the key technology for future space-based X-ray observatories and ground-based experiments in the fields of astrophysics, laboratory astrophysics, plasma physics, particle physics and material analysis. Thanks to their sharp superconducting-to-normal transition, TESs can achieve very high sensitivity in detecting small temperature changes at very low temperature. TES based X-ray detectors are non-dispersive spectrometers bringing together high resolving power, imaging capability and high-quantum efficiency simultaneously. In this chapter, we highlight the basic principles behind the operation and design of TESs, and their fundamental noise limits. We will further elaborate on the key fundamental physics processes that guide the design and optimization of the detector. We will then describe pulse-processing and important calibration considerations for space flight instruments, before introducing novel multi-pixel TES designs and discussing applications in future X-ray space missions over the coming decades.