Development of Low-Power dc-SQUIDs for TES Frequency-Division Multiplexing Readout Towards Future Space Missions

We are developing low-power dc-SQUIDs to read out TES X-ray microcalorimeter arrays with frequency-division multiplexing (FDM) towards future X-ray satellite missions. In future space missions, large-format TES X-ray microcalorimeter arrays with hundreds to thousands of pixels are promising detectors achieving high energy resolution and high spatial resolution at the same time. To read out such a large-format array with a limited cooling power at the cryogenic stage, TES pixels are multiplexed in the frequency domain and read out using SQUIDs with small heat dissipations. We are developing low-powered dc-SQUIDs with an adequate gain and a low noise characteristic for TES FDM readouts. With these features, the SQUID can suffice to be the only amplifier in the cold electronics even though it can be placed at the cryogenic stage below 100 mK, enabling a simple single-staged cryogenic configuration. Using the low-power SQUID, we are developing multi-input SQUID chips with built-in bandpass filters used for the channel separation in FDM. Within the size of 2.5×2.5 mm, it carries the low-power SQUID, a TES shunt resistor, and LC bandpass filters for four channels. We are also developing a same-size extension chip that consists of the bandpass filters for four other channels, and it can be attached to the multi-input SQUID chip with only two bonding wires. With these chips, the cryogenic stage setup is drastically simplified. The designs and experimental results of the SQUIDs will be discussed.