Nuclear magnetic resonance experiments with dc SQUID amplifiers
- California Univ., Berkeley, CA (USA). Dept. of Physics Lawrence Berkeley Lab., CA (USA)
The development and fabrication of dc SQUIDs (Superconducting QUantum Interference Devices) with Nb/Al{sub 2}O{sub 3}/Nb Josephson junctions is described. A theory of the dc SQUID as a radio-frequency amplifier is presented, with an optimization strategy that accounts for the loading and noise contributions of the postamplifier and maximizes the signal-to-noise ratio of the total system. The high sensitivity of the dc SQUID is extended to high field NMR. A dc SQUID is used as a tuned radio-frequency amplifier to detect pulsed nuclear magnetic resonance at 32 MHz from a metal film in a 3.5 Tesla static field. A total system noise temperature of 11 K has been achieved, at a bath temperature of 4.2 K. The minimum number of nuclear Bohr magnetons observable from a free precession signal after a single pulse is about 2 {times} 10{sup 17} in a bandwidth of 25 kHz. In a separate experiment, a dc SQUID is used as a rf amplifier in a NQR experiment to observe a new resonance response mechanism. The net electric polarization of a NaClO{sub 3} crystal due to the precessing electric quadrupole moments of the Cl nuclei is detected at 30 MHz. The sensitivity of NMR and NQR spectrometers using dc SQUID amplifiers is compared to the sensitivity of spectrometers using conventional rf amplifiers. A SQUID-based spectrometer has a voltage sensitivity which is comparable to the best achieved by a FET-based spectrometer, at these temperatures and operating frequencies.
- Research Organization:
- Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
- Sponsoring Organization:
- USDOE; USDOE, Washington, DC (USA)
- DOE Contract Number:
- AC03-76SF00098
- OSTI ID:
- 6102726
- Report Number(s):
- LBL-30095; ON: DE91009775; TRN: 91-008770
- Resource Relation:
- Other Information: Thesis (Ph.D.)
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
SUPERCONDUCTIVITY AND SUPERFLUIDITY
46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND TECHNOLOGY
NMR SPECTROMETERS
SQUID DEVICES
NUCLEAR MAGNETIC RESONANCE
DESIGN
AMPLIFIERS
ELECTRONIC CIRCUITS
JOSEPHSON JUNCTIONS
LEAD
RF SYSTEMS
STARK EFFECT
ELECTRONIC EQUIPMENT
ELEMENTS
EQUIPMENT
FLUXMETERS
JUNCTIONS
MAGNETIC RESONANCE
MEASURING INSTRUMENTS
METALS
MICROWAVE EQUIPMENT
RESONANCE
SPECTROMETERS
SUPERCONDUCTING DEVICES
SUPERCONDUCTING JUNCTIONS
426001* - Engineering- Superconducting Devices & Circuits- (1990-)
440101 - Radiation Instrumentation- General Detectors or Monitors & Radiometric Instruments