High sensitivity double relaxation oscillation superconducting quantum interference devices with large transfer from flux to voltage
- Electrotechnical Laboratory, 1-1-4 Umezono, Tsukuba 303 (Japan)
Double relaxation oscillation superconducting quantum interference devices (SQUIDs) (DROSs) based on Nb/AlO{sub {ital x}} tunnel junctions have been fabricated and characterized. The estimated relaxation frequencies range from 400 MHz up to 14 GHz. Transfer coefficients from flux to voltage of 2 up to 7 mV/{phi}{sub 0} have been obtained. Both the intrinsic flux noise and the performance in a flux-locked loop with direct-voltage readout have been determined. Special attention is paid to the effect of damping resistors on the sensitivity of DROSs. The intrinsic sensitivity improves with increasing relaxation frequency, leveling off to a value of 13{ital h} at relaxation frequencies above 2--3 GHz for SQUID inductances of about 30 pH. This sensitivity is very close to the theoretical maximum sensitivity of 6{ital h} of a comparable standard type dc SQUID. In a flux-locked loop based on direct-voltage readout, a noise level of 0.55 {mu}{phi}{sub 0}/{radical}Hz corresponding to an energy sensitivity of 34{ital h} has been obtained for a DROS with a SQUID inductance of 29 pH. {copyright} {ital 1995} {ital American} {ital Institute} {ital of} {ital Physics}.
- OSTI ID:
- 165062
- Journal Information:
- Review of Scientific Instruments, Vol. 66, Issue 3; Other Information: PBD: Mar 1995
- Country of Publication:
- United States
- Language:
- English
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