On-Sky Performance of the SPT-3G Frequency-Domain Multiplexed Readout
Abstract
Frequency-domain multiplexing (fMux) is an established technique for the readout of large arrays of transition-edge sensor (TES) bolometers. Each TES in a multiplexing module has a unique AC voltage bias that is selected by a resonant filter. This scheme enables the operation and readout of multiple bolometers on a single pair of wires, reducing thermal loading onto sub-Kelvin stages. The current receiver on the South Pole Telescope, SPT-3G, uses a 68x fMux system to operate its large-format camera of ∼16,000 TES bolometers. We present here the successful implementation and performance of the SPT-3G readout as measured on-sky. Characterization of the noise reveals a median pair-differenced 1/f knee frequency of 33 mHz, indicating that low-frequency noise in the readout will not limit SPT-3G's measurements of sky power on large angular scales. Measurements also show that the median readout white noise level in each of the SPT-3G observing bands is below the expectation for photon noise, demonstrating that SPT-3G is operating in the photon-noise-dominated regime.
- Publication:
-
Journal of Low Temperature Physics
- Pub Date:
- April 2020
- DOI:
- 10.1007/s10909-019-02280-w
- arXiv:
- arXiv:1907.10947
- Bibcode:
- 2020JLTP..199..182B
- Keywords:
-
- Frequency-domain multiplexing;
- Transition-edge sensor;
- Cosmic microwave background;
- Astrophysics - Instrumentation and Methods for Astrophysics;
- Physics - Instrumentation and Detectors
- E-Print:
- 9 pages, 5 figures submitted to the Journal of Low Temperature Physics: LTD18 Special Edition