Mapping TES Temperature Sensitivity and Current Sensitivity as a Function of Temperature, Current, and Magnetic Field with IV Curve and Complex Admittance Measurements

Abstract

We have specialized astronomical applications for X-ray microcalorimeters with superconducting transition edge sensors (TESs) that require exceptionally good TES performance, but which operate in the small-signal regime. We have therefore begun a program to carefully characterize the entire transition surface of TESs with and without the usual zebra stripes to see if there are reproducible local "sweet spots" where the performance is much better than average. These measurements require precise knowledge of the circuit parameters. Here, we show how the Shapiro effect can be used to precisely calibrate the value of the shunt-resistor. We are also investigating the effects of stress and external magnetic fields to better understand reproducibility problems.

A Review of X-ray Microcalorimeters Based on Superconducting Transition Edge Sensors for Astrophysics and Particle Physics

“…The common practice to discriminate whether a TES behaves as a weakly-linked or strong superconductor has been so far to look for the exponential behaviour of the I c (T), its Fraunhofer-like behaviour as a function of the perpendicular magnetic field, the oscillatory features in the TES reactance as a function of the MHz voltage bias TES [36], or the presence of Shapiro-steps in dc bias TES under MHz current or magnetic field excitation [44][45][46]. The latter effect, for example, manifest itself with a specific current step pattern in the TES IV curves at V m,n = m/nhω/2e, according to the Josephson law.…”

“…However, it can be used to calculate the TES response to a small, |V ac | << V dc , ac excitation, or to evaluate the impact on the weak-link TES of electro-magnetic interferences (EMI) coupled to the bias line, by assuming, for example, V ac (t) = V pk cos(ω EMI t). Interesting enough, by adding to the bias line a controlled small signal at a fixed MHz frequency, Shapiro steps can be observed in the TES IV characteristics, according to Equation ( 16), and the position of the steps can be used to accurately calibrate the TES voltage [44][45][46].…”