Single SQUID multiplexer for arrays of voltage-biased superconducting bolometers
We describe a frequency domain superconducting quantum interference device (SQUID) multiplexer which monitors a row of low-temperature sensors simultaneously with a single SQUID. Each sensor is ac biased with a unique frequency and all the sensor currents are added in a superconducting summing loop. A single SQUID measures the current in the summing loop, and the individual signals are lock-in detected after the room temperature SQUID electronics. The current in the summing loop is nulled by feedback to eliminate direct crosstalk. In order to avoid the accumulation of Johnson noise in the summing loop, a tuned bandpass filter is inserted in series with each sensor. For a 32-channel multiplexer for Voltage-biased Superconducting Bolometer (VSB) with a time constant {approx}1msec, we estimate that bias frequencies in the range from {approx}500kHz to {approx}600kHz are practical. The major limitation of our multiplexing scheme is in the slew rate of a readout SQUID. We discuss a ''carrier nulling'' technique which could be used to increase the number of sensors in a row or to multiplex faster bolometers by reducing the required slew rate for a readout SQUID.
- Research Organization:
- Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
- Sponsoring Organization:
- USDOE Director, Office of Science. Office of Basic Energy Studies; National Aeronautics and Space Administration (US)
- DOE Contract Number:
- AC03-76SF00098
- OSTI ID:
- 787157
- Report Number(s):
- LBNL-48677; R&D Project: 505401; TRN: AH200134%%186
- Resource Relation:
- Conference: 9th International Workshop on Low Temperature Detectors, LTD-9, Madison, WI (US), 07/23/2001--07/27/2001; Other Information: PBD: 20 Aug 2001
- Country of Publication:
- United States
- Language:
- English
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