Performance of an X-ray single pixel TES microcalorimeter under DC and AC biasing

Abstract

We are developing Frequency Domain Multiplexing (FDM) for the read‐out of TES imaging microcalorimeter arrays for future X‐ray missions like IXO. In the FDM configuration the TES is AC voltage biased at a well defined frequencies (between 0.3 to 10 MHz) and acts as an AM modulating element. In this paper we will present a full comparison of the performance of a TES microcalorimeter under DC bias and AC bias at a frequency of 370 kHz. In both cases we measured the current‐to‐voltage characteristics, the complex impedance, the noise, the X‐ray responsivity, and energy resolution. The behaviour is very similar in both cases, but deviations in performances are observed for detector working points low in the superconducting transition (R/RN<0.5). The measured energy resolution at 5.89 keV is 2.7 eV for DC bias and 3.7 eV for AC bias, while the baseline resolution is 2.8 eV and 3.3 eV, respectively.