Improved Performance of TES Bolometers using Digital Feedback

Abstract

Voltage biased, frequency multiplexed TES bolometers have become a widespread tool in mm-wave astrophysics. However, parasitic impedance and dynamic range issues can limit stability, performance, and multiplexing factors. Here, we present novel methods of overcoming these challenges, achieved through digital feedback, implemented on a Field-Programmable Gate Array (FPGA). In the first method, known as Digital Active Nulling (DAN), the current sensor (e.g. SQUID) is nulled in a separate digital feedback loop for each bolometer frequency. This nulling removes the dynamic range limitation on the current sensor, increases its linearity, and reduces its effective input impedance. Additionally, DAN removes constraints on wiring lengths and maximum multiplexing frequency. DAN has been fully implemented and tested. Integration for current experiments, including the South Pole Telescope, will be discussed. We also present a digital mechanism for strongly increasing stability in the presence of large series impedances, known as Digitally Enhanced Voltage Bias (DEVB).

References in corpus (6)

• Measurements of Secondary Cosmic Microwave Background Anisotropies with the South Pole Telescope
• Frequency Multiplexed SQUID Readout of Large Bolometer Arrays for Cosmic Microwave Background Measurements
• Digital Frequency Domain Multiplexer for mm-Wavelength Telescopes
• Millimeter-wave bolometer array receiver for the Atacama pathfinder experiment Sunyaev-Zel'dovich (APEX-SZ) instrument
• The new generation CMB B-mode polarization experiment: POLARBEAR
• Biasing and Demodulation Firmware for Kilopixel TES Bolometer Arrays

Cited by in corpus (30)

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• PICO: Probe of Inflation and Cosmic Origins
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• Measurements of E-Mode Polarization and Temperature-E-Mode Correlation in the Cosmic Microwave Background from 100 Square Degrees of SPTpol Data
• Year two instrument status of the SPT-3G cosmic microwave background receiver
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• Recent Advances in Frequency-Multiplexed TES Readout: Vastly Reduced Parasitics and an Increase in Multiplexing Factor with sub-Kelvin SQUIDs
• Development and characterization of the readout system for POLARBEAR-2
• Design and Bolometer Characterization of the SPT-3G First-year Focal Plane
• Frequency Shift Algorithm: Design of a Baseband Phase Locked Loop for Frequency-Domain Multiplexing Readout of X-ray Transition-Edge Sensor Microcalorimeters
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• The Design and Integrated Performance of SPT-3G
• Readout noise of digital frequency multiplexed TES detectors for CUPID