Development of readout electronics for POLARBEAR-2 Cosmic Microwave Background experiment

Understand

The readout of transition-edge sensor (TES) bolometers with a large multiplexing factor is key for the next generation Cosmic Microwave Background (CMB) experiment, Polarbear-2, having 7,588 TES bolometers.

• To enable the large arrays, we have been developing a readout system with a multiplexing factor of 40 in the frequency domain.
• Extending that architecture to 40 bolometers requires an increase in the bandwidth of the SQUID electronics above 4 MHz.
• This paper focuses on cryogenic readout and shows how it affects cross talk and the responsivity of the TES bolometers.