Full-Chip Thermal Simulation of Superconductor Transition-Edge Sensor Circuits

In order to gain a better understanding of heat conduction in superconductor transition-edge sensor (TES) circuits and its interplay with their electrical behavior, we develop methods and techniques for full-chip thermal simulation of TES circuits. Instead of using a finite difference or finite element approach, we solve for the Green function of substrate temperature distribution for a point heat source on the surface of the chip. By properly incorporating electrothermal feedback in our thermal model, we are able to determine the temperature and heat flow anywhere in the chip, together and self-consistently with the electrical signals. Accurate and much more efficient than finite difference or finite element calculations, our method reveals much more detailed information about heat conduction in TES circuits than does the simplified power-law approximation and thus is valuable for optimizing their design and operation.