Frequency domain multiplexing for bolometer arrays

Fabrication of arrays of a thousand or more sensors is becoming practical. However, readout of these arrays remains a major instrumental challenge. We address this challenge using frequency-domain multiplexing of signals from an array of superconducting transition-edge sensors (TES). Each TES sensor is connected in series with an LC tuned circuit and biased with an alternating current at a selected frequency, ranging from 380 kHz to 1 MHz.The signal from each sensor amplitude-modulates its respective bias current. The LC filter reduces the bandwidth of the Johnson noise from the remaining sensors. The signals are combined at a current summing node and measured with a single superconducting quantum interference device (SQUID) array (100 elements). We have developed a custom SQUID controller with a measured slew rate of 107 Φ0/s at 1 MHz. igned and fabricated photolithographed LC filters. With these filters we have demonstrated multiplexing with two TES sensors and are preparing to scale up to 32 sensors.