A Spread-Spectrum SQUID Multiplexer
The transition-edge sensor (TES) is a mature, high-resolution x-ray spectrometer technology that provides a much higher efficiency than dispersive spectrometers such as gratings and crystal spectrometers. As larger arrays are developed, time-division multiplexing schemes operating at MHz frequencies are being replaced by microwave SQUID multiplexers using frequency-division multiplexing at GHz frequencies. However, the multiplexing factor achievable with microwave SQUIDs is limited by the high slew rate on the leading edge of x-ray pulses. In this paper, we propose a new multiplexing scheme for high-slew-rate TES x-ray calorimeters: the spread-spectrum SQUID multiplexer, which has the potential to enable higher multiplexing factors, especially in applications with lower photon-arrival rates.
Irwin, K. D., Chaudhuri, S., Cho, H.-M., Dawson, C., Kuenstner, S., Li, D., Titus, C. J., & Young, B. A. (2018). A Spread-Spectrum SQUID Multiplexer. Journal of Low Temperature Physics, 193(3), 476–484. https://doi.org/10.1007/s10909-018-1987-z