Development of a microwave SQUID multiplexer for magnetic microbolometers

Abstract: The search for primordial B-modes in the cosmic microwave background (CMB) requires highly sensitive and scalable detector systems. The magnetic microbolometer (MMB) is an emerging detector concept that exploits the magnetic properties of paramagnetic materials at sub-kelvin temperatures, offering bolometers with a high dynamic range and low intrinsic noise. In recent years, the microwave SQUID multiplexer ($\mu$MUX) has become a key technology to efficiently read large low temperature detector arrays, enabling the readout of hundreds to thousands of detectors over a single transmission line with low noise and minimal power dissipation while reducing the cryogenic setup complexity. In this work, we report the design, fabrication and characterization of a $\mu$MUX optimized for MMB detectors and share our latest experimental results from a bolometer prototype. These findings provide valuable insight of the $\mu$MUX in advancing next-generation CMB instrumentation and also demonstrate its suitability for novel detector technologies such as the MMB.