Understanding Flux Dynamics in Transition Edge Sensors for Superconducting Photon Detectors

Superconducting Transition Edge Sensors (TESs) can be used to detect the absorption of extremely small amounts of energy, and today form the basis of cutting edge sensors in applications ranging in energy from gamma ray detectors for nuclear physics all the way down to single photon detectors and near-infrared spectrometers. Such applications would benefit greatly from TESs which operate with higher detection efficiency and energy resolution, while also being faster and/or more robust. However, the mechanisms which currently limit TES performance in these respects remain poorly understood, especially in applications where stray magnetic fields cannot be avoided. To make progress, we first need to better understand the fundamental device physics of TESs and develop the means to relate their superconducting dynamics with their operational behavior.

We have begun to explore this via a combined theory and experimental program designed around emerging models being developed at NIST using the Time-Dependent Ginzburg-Landau (TDGL) equations to simulate flux dynamics in realistic TES geometries. To do this, we employ high-quality device measurements and magneto-transport to study the material properties and device characteristics of TESs, which in turn informs our TDGL models of their superconductivity and allows for the predictive design of more optimal TESs. This iterative process is hoped to improve our understanding of the intrinsically dynamic thermal and magnetic properties of TESs which are not currently captured in existing models due to their complex material and geometric dependencies.