Integration of TES Microcalorimeters With Microwave SQUID Multiplexed Readout

The demonstration of a microwave superconducting quantum interference device (SQUID) multiplexed readout of transition-edge sensor (TES) microcalorimeters has the potential to dramatically expand the scale of arrays of TESs. In this paper, we discuss recent work to develop an instrument for high-resolution high-efficiency gamma-ray spectroscopy that integrates previously demonstrated high-resolution TES microcalorimeters with new lower noise microwave SQUID multiplexers. We will discuss the proposed instrument design and readout noise of the optimized microwave SQUID multiplexed readout. Finally, we will discuss the potential limits on the number of multiplexed TESs imposed by the analog-to-digital converter.