title: High-sensitivity cooled coil system for nuclear magnetic resonance in kHz range.
abstract: In several low-field Nuclear Magnetic Resonance (LF-NMR) and surface nuclear magnetic resonance applications, i.e., in the frequency range of kHz, high sensitivity magnetic field detectors are needed. Usually, low-Tc superconducting quantum interference devices (SQUIDs) with a high field sensitivity of about 1 fT/Hz(1/2) are employed as detectors. Considering the flux trapping and operational difficulties associated with low-Tc SQUIDs, we designed and fabricated liquid-nitrogen-cooled Cu coils for NMR detection in the kHz range. A cooled coil system consisting of a 9-cm diameter Cu coil and a low noise preamplifier was systematically investigated and reached a sensitivity of 2 fT/Hz(1/2) at 77 K, which is 3 times better compared to the sensitivity at 300 K. A Q-switch circuit as an essential element for damping the ringing effects of the pickup coil was developed to acquire free induction decay signals of a water sample with minimum loss of signal. Our studies demonstrate that cooled Cu coils, if designed properly, can provide a comparable sensitivity to low-Tc SQUIDs.
authors.affiliation: College of Instrumentation and Electrical Engineering, Jilin University, Changchun 130061, China.
authors.forename: Tingting
authors.initials: T
authors.lastname: Lin
authors.affiliation: Peter Grünberg Institute (PGI-8), Forschungszentrum Jülich (FZJ), D-52425 Jülich, Germany.
authors.forename: Yi
authors.initials: Y
authors.lastname: Zhang
authors.affiliation: Peter Grünberg Institute (PGI-8), Forschungszentrum Jülich (FZJ), D-52425 Jülich, Germany.
authors.forename: Yong-Ho
authors.initials: YH
authors.lastname: Lee
authors.affiliation: Peter Grünberg Institute (PGI-8), Forschungszentrum Jülich (FZJ), D-52425 Jülich, Germany.
authors.forename: Hans-Joachim
authors.initials: HJ
authors.lastname: Krause
authors.affiliation: College of Instrumentation and Electrical Engineering, Jilin University, Changchun 130061, China.
authors.forename: Jun
authors.initials: J
authors.lastname: Lin
authors.affiliation: College of Instrumentation and Electrical Engineering, Jilin University, Changchun 130061, China.
authors.forename: Jing
authors.initials: J
authors.lastname: Zhao
mesh_terms: D009682:Magnetic Resonance Spectroscopy / Q000295:instrumentation*; D008962:Models, Theoretical