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Title: Optical fiber feedback SQUID magnetometer

Abstract

This paper describes an optical fiber feedback superconducting quantum interference device (SQUID) magnetometer which was developed to improve electromagnetic interference characteristics. The SQUID consists of an RF SQUID probe, an RF amplifier, two multimode fibers, and a SQUID control unit. Phase-locked pulse width modulation (PWM) was used to construct a flux locked loop (FLL) circuit in the SQUID control unit. The operation of the optical fiber feedback SQUID is stable when a common mode voltage of ac 100 V/50 Hz is applied. It has an energy resolution of 1 x 10/sup -28/ J/Hz. This paper also describes the measurement of an auditory evoked field from the human brain in a magnetically shielded room using the fiber feedback SQUID with a gradiometer type pickup coil.

Authors:
; ;  [1]
  1. (Yokogawa Electric Corp., 2-9-32, Nakacho, Musashino-shi, Tokyo 180 (JP))
Publication Date:
OSTI Identifier:
5169747
Resource Type:
Journal Article
Resource Relation:
Journal Name: IEEE (Institute of Electrical and Electronics Engineers) Transactions on Instrumentation and Measurement; (USA); Journal Volume: 38:2
Country of Publication:
United States
Language:
English
Subject:
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; BRAIN; MAGNETIC FIELDS; MAGNETOMETERS; DESIGN; OPTICAL FIBERS; SUPERCONDUCTIVITY; SQUID DEVICES; ACOUSTIC MEASUREMENTS; ELECTROMAGNETIC PULSES; ELECTRONIC CIRCUITS; FEEDBACK; HUMAN POPULATIONS; MAGNETIC SHIELDING; MICROWAVE AMPLIFIERS; MODE LOCKING; PERFORMANCE; AMPLIFIERS; BODY; CENTRAL NERVOUS SYSTEM; ELECTRIC CONDUCTIVITY; ELECTRICAL PROPERTIES; ELECTROMAGNETIC RADIATION; ELECTRONIC EQUIPMENT; EQUIPMENT; FIBERS; FLUXMETERS; MEASURING INSTRUMENTS; MICROWAVE EQUIPMENT; NERVOUS SYSTEM; ORGANS; PHYSICAL PROPERTIES; POPULATIONS; PULSES; RADIATIONS; SHIELDING; SUPERCONDUCTING DEVICES; 426001* - Engineering- Superconducting Devices & Circuits- (1990-)

Citation Formats

Naito, S., Sampei, Y., and Takahashi, T.. Optical fiber feedback SQUID magnetometer. United States: N. p., 1989. Web. doi:10.1109/19.192358.
Naito, S., Sampei, Y., & Takahashi, T.. Optical fiber feedback SQUID magnetometer. United States. doi:10.1109/19.192358.
Naito, S., Sampei, Y., and Takahashi, T.. Sat . "Optical fiber feedback SQUID magnetometer". United States. doi:10.1109/19.192358.
@article{osti_5169747,
title = {Optical fiber feedback SQUID magnetometer},
author = {Naito, S. and Sampei, Y. and Takahashi, T.},
abstractNote = {This paper describes an optical fiber feedback superconducting quantum interference device (SQUID) magnetometer which was developed to improve electromagnetic interference characteristics. The SQUID consists of an RF SQUID probe, an RF amplifier, two multimode fibers, and a SQUID control unit. Phase-locked pulse width modulation (PWM) was used to construct a flux locked loop (FLL) circuit in the SQUID control unit. The operation of the optical fiber feedback SQUID is stable when a common mode voltage of ac 100 V/50 Hz is applied. It has an energy resolution of 1 x 10/sup -28/ J/Hz. This paper also describes the measurement of an auditory evoked field from the human brain in a magnetically shielded room using the fiber feedback SQUID with a gradiometer type pickup coil.},
doi = {10.1109/19.192358},
journal = {IEEE (Institute of Electrical and Electronics Engineers) Transactions on Instrumentation and Measurement; (USA)},
number = ,
volume = 38:2,
place = {United States},
year = {Sat Apr 01 00:00:00 EST 1989},
month = {Sat Apr 01 00:00:00 EST 1989}
}
  • From the Green's function for the magnetic scalar potential inside an infinitely long superconducting shield, an expression is obtained for the flux within a circular pickup coil due to a cylindrical sample of arbitrary dimensions. Using this expression, the dependence of SQUID output on sample dimensions and pickup coil and shield radii is derived. The predictions are found to be in good agreement with experimental measurements.
  • A self-sustained oscillation of laser light intensity emitted by a laser diode was newly observed by a delayed network using an optical fiber and an electrical feedback system. The time delay (transit time) of the light beam through the optical fiber plus the time delay of the electrical signal in the electrical feedback system determines the oscillation frequency of the light intensity. The oscillation for the fiber length of 7 km was obtained by using an electrical amplifier with large gain. With a wide-band amplifier, harmonic (multimode) oscillations took place where the waveform was almost square.
  • A novel optical feedback method is described for suppressing self-sustained pulsations in semiconductor lasers. Using an external cavity formed from a single segment of optical fiber about 1 cm long, a few percent of the light is coupled back into the laser cavity. All pulsations are suppressed, independently of the pulsation frequency. This behavior is predicted by a model which incorporates saturable absorption centers in the laser cavity.
  • The electronic recording unit of a squid-based magnetometer is described. The unit consists of an rf head, mounted tightly on a cyrogenic insert, and a control module. The input stage of a wide-band rf amplifier with a tunable resonant filter is built on a KF910 low-noise MOS transistor and has spectral densities of the noise voltage and current, adjusted to the input, of 1.7 nVHz/sup 1/2 and 0.95 pAHz/sup 1/2. The noise corresponds to a flux resolution of 5 x 10/sup -4/ Phi/sub 0/ Hz/sup -1/2 or a magnetic-moment resolution of 2.5 x 10/sup -13/ A x m/sup 2/Hz/sup 1/2/.
  • We have constructed optimized high {ital T}{sub {ital c}} YBa{sub 2}Cu{sub 3}O{sub 7} (YBCO) multiturn flux transformers using laser-deposited films patterned with ion milling and only photolithographic masking. A five-turn flux transformer with a 0.5{times}0.5 mm{sup 2} pickup loop was coupled to a YBCO superconducting quantum interference device (SQUID) made on a separate substrate to demonstrate a prototype high {ital T}{sub {ital c}} SQUID magnetometer with all components working at 77 K. There was no additional noise associated with the input coil and transformer. The magnetic field sensitivity of the 0.5{times}0.5 mm{sup 2} magnetometer was 3.8 pT/{radical}Hz at 77 Kmore » and 1 kHz.« less