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Title: Optical fiber feedback SQUID magnetometer

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-)