SQUID linearization by current-sampling feedback

Research output: Contribution to journalArticleScientificpeer-review

20 Citations (Scopus)

Abstract

Local negative feedback derived within the cryogenic stage from the output current of a voltage-biased SQUID series array is used to linearize the flux response and to simultaneously approach the noise matching resistance of the room temperature readout amplifier. The flux noise level of the SQUID array was 0.5 μΦ0 Hz−1/2 in open loop and 0.8 μΦ0 Hz−1/2 in the feedback arrangement having a 2.2 Φ0 peak-to-peak flux locking range. The noise level degraded to 2 μΦ0 Hz−1/2 in an arrangement with a 7Φ0 locking range. Very good linearity was observed in the feedback system regardless of the modest loop gain, owing to the open-loop SQUID characteristics which are more linear in the voltage-biased case than in the current-biased case. Upward and downward slew rates of 3.4 and 1.2Φ0 µs−1 were recorded which, however, do not represent ultimate limits of the approach. Local feedback schemes are reviewed and their effect on the linearity of a SQUID system is discussed.
Original languageEnglish
Article number045009
Number of pages6
JournalSuperconductor Science and Technology
Volume21
Issue number4
DOIs
Publication statusPublished - 2008
MoE publication typeA1 Journal article-refereed

Fingerprint

SQUIDs
linearization
Linearization
sampling
Sampling
Feedback
locking
linearity
Fluxes
negative feedback
electric potential
cryogenics
readout
Electric potential
amplifiers
Cryogenics
output
room temperature
Temperature

Keywords

  • SQUID
  • SQUID arrays
  • quantum interference
  • quantum interference phenomena

Cite this

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title = "SQUID linearization by current-sampling feedback",
abstract = "Local negative feedback derived within the cryogenic stage from the output current of a voltage-biased SQUID series array is used to linearize the flux response and to simultaneously approach the noise matching resistance of the room temperature readout amplifier. The flux noise level of the SQUID array was 0.5 μΦ0 Hz−1/2 in open loop and 0.8 μΦ0 Hz−1/2 in the feedback arrangement having a 2.2 Φ0 peak-to-peak flux locking range. The noise level degraded to 2 μΦ0 Hz−1/2 in an arrangement with a 7Φ0 locking range. Very good linearity was observed in the feedback system regardless of the modest loop gain, owing to the open-loop SQUID characteristics which are more linear in the voltage-biased case than in the current-biased case. Upward and downward slew rates of 3.4 and 1.2Φ0 µs−1 were recorded which, however, do not represent ultimate limits of the approach. Local feedback schemes are reviewed and their effect on the linearity of a SQUID system is discussed.",
keywords = "SQUID, SQUID arrays, quantum interference, quantum interference phenomena",
author = "Mikko Kiviranta",
year = "2008",
doi = "10.1088/0953-2048/21/4/045009",
language = "English",
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journal = "Superconductor Science and Technology",
issn = "0953-2048",
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}

SQUID linearization by current-sampling feedback. / Kiviranta, Mikko.

In: Superconductor Science and Technology, Vol. 21, No. 4, 045009, 2008.

Research output: Contribution to journalArticleScientificpeer-review

TY - JOUR

T1 - SQUID linearization by current-sampling feedback

AU - Kiviranta, Mikko

PY - 2008

Y1 - 2008

N2 - Local negative feedback derived within the cryogenic stage from the output current of a voltage-biased SQUID series array is used to linearize the flux response and to simultaneously approach the noise matching resistance of the room temperature readout amplifier. The flux noise level of the SQUID array was 0.5 μΦ0 Hz−1/2 in open loop and 0.8 μΦ0 Hz−1/2 in the feedback arrangement having a 2.2 Φ0 peak-to-peak flux locking range. The noise level degraded to 2 μΦ0 Hz−1/2 in an arrangement with a 7Φ0 locking range. Very good linearity was observed in the feedback system regardless of the modest loop gain, owing to the open-loop SQUID characteristics which are more linear in the voltage-biased case than in the current-biased case. Upward and downward slew rates of 3.4 and 1.2Φ0 µs−1 were recorded which, however, do not represent ultimate limits of the approach. Local feedback schemes are reviewed and their effect on the linearity of a SQUID system is discussed.

AB - Local negative feedback derived within the cryogenic stage from the output current of a voltage-biased SQUID series array is used to linearize the flux response and to simultaneously approach the noise matching resistance of the room temperature readout amplifier. The flux noise level of the SQUID array was 0.5 μΦ0 Hz−1/2 in open loop and 0.8 μΦ0 Hz−1/2 in the feedback arrangement having a 2.2 Φ0 peak-to-peak flux locking range. The noise level degraded to 2 μΦ0 Hz−1/2 in an arrangement with a 7Φ0 locking range. Very good linearity was observed in the feedback system regardless of the modest loop gain, owing to the open-loop SQUID characteristics which are more linear in the voltage-biased case than in the current-biased case. Upward and downward slew rates of 3.4 and 1.2Φ0 µs−1 were recorded which, however, do not represent ultimate limits of the approach. Local feedback schemes are reviewed and their effect on the linearity of a SQUID system is discussed.

KW - SQUID

KW - SQUID arrays

KW - quantum interference

KW - quantum interference phenomena

U2 - 10.1088/0953-2048/21/4/045009

DO - 10.1088/0953-2048/21/4/045009

M3 - Article

VL - 21

JO - Superconductor Science and Technology

JF - Superconductor Science and Technology

SN - 0953-2048

IS - 4

M1 - 045009

ER -