Demonstration of MHz frequency domain multiplexing readout of 37 transition edge sensors for high-resolution x-ray imaging spectrometers

TL;DR

This paper demonstrates a MHz frequency domain multiplexing method for reading out large arrays of cryogenic TES X-ray microcalorimeters, achieving high spectral resolution and multiplexing of 37 pixels, with potential for further improvements.

Contribution

The paper introduces a MHz FDM technique for TES array readout, enabling high-resolution X-ray spectroscopy with increased multiplexing capability.

Findings

Successfully multiplexed 37 TES pixels.

Achieved spectral resolution of ~2.2 eV at 5.9 keV.

Comparable performance to other multiplexing methods.

Abstract

We report on the development and demonstration of a MHz frequency domain multiplexing (FDM) technology to read out arrays of cryogenic transition edge sensor (TES) X-ray microcalorimeters. In our FDM scheme, TESs are AC-biased at different resonant frequencies in the low MHz range through an array of high-$Q$ LC resonators. The current signals of all TESs are summed at superconducting quantum interference devices (SQUIDs). We have demonstrated multiplexing for a readout of 31 pixels using room temperature electronics, high-$Q$ LC filters and TES arrays developed at SRON, and SQUID arrays from VTT. We repeated this on a second setup with 37 pixels. The summed X-ray spectral resolutions $@$ 5.9 keV are $\Delta E_{\rm 31 pix ~MUX}=2.14\pm0.03$ eV and $\Delta E_{\rm 37 pix ~MUX}=2.23\pm0.03$ eV. The demonstrated results are comparable with other multiplexing approaches. There is potential to further improve the spectral resolution and to increase the number of multiplexed TESs, and to open up applications for TES X-ray microcalorimeters.