title: High temperature RF SQUIDs for biomedical applications.
abstract: We have been investigating the feasibility of radio-frequency RF, low-noise superconducting quantum interference device (SQUID) magnetometers and gradiometers operating in liquid nitrogen at 77 K. Using flux-focusing structures fabricated from epitaxial YBa2Cu3O7-chi films, we have attained a magnetic field resolution for a magnetometer of better than 200 fT Hz-1/2 at less than 1 Hz, i.e. over the low signal-frequency range important for biomedical diagnostics. At 77 K, this magnetometer recorded diagnostically useful heart signals, voluntary eye-blink signals, and also the first evoked response of a human brain. These and similar results were obtained in a magnetically shielded room. We were also able to record heart signals in the absence of any shielding when using a first-order gradiometer. An improvement in the magnetic field resolution of our magnetometers and gradiometers by, at least, another order of magnitude is possible and probable.
authors.affiliation: Forschungszentrum Jülich, Institut für Schicht- and Ionentechnik (ISI), Germany.
authors.forename: Y
authors.initials: Y
authors.lastname: Zhang
authors.forename: Y
authors.initials: Y
authors.lastname: Tavrin
authors.forename: M
authors.initials: M
authors.lastname: Mück
authors.forename: A I
authors.initials: AI
authors.lastname: Braginski
authors.forename: C
authors.initials: C
authors.lastname: Heiden
authors.forename: T
authors.initials: T
authors.lastname: Elbert
authors.forename: S
authors.initials: S
authors.lastname: Hampson
mesh_terms: D004553:Electric Conductivity; D006334:Heart Function Tests / Q000295:instrumentation*; D006801:Humans; D008280:Magnetics; D015225:Magnetoencephalography / Q000295:instrumentation*; D008297:Male