Nuclear magnetic resonance with dc SQUID (Super-conducting QUantum Interference Device) preamplifiers

Conference · Mon Aug 01 04:00:00 EDT 1988

OSTI ID:6225439

Fan, N Q; Heaney, M B; Clark, J; Newitt, D; Wald, L; Hahn, E L; Bierlecki, A; Pines, A

Sensitive radio-frequency (rf) amplifiers based on dc Superconducting QUantum Interface Devices (SQUIDS) are available for frequencies up to 200 MHz. At 4.2 K, the gain and noise temperature of a typical tuned amplifier are 18.6 +- 0.5 dB and 1.7 +- 0.5 K at 93 MHz. These amplifiers are being applied to a series of novel experiments on nuclear magnetic resonance (NMR) and nuclear quadrupole resonance (NQR). The high sensitivity of these amplifiers was demonstrated in the observation of ''nuclear spin noise'', the emission of photons by /sup 35/Cl nuclei in a state of zero polarization. In the more conventional experiments in which one applies a large rf pulse to the spins, a Q-spoiler, consisting of a series array of Josephson junctions, is used to reduce the Q of the input circuit to a very low value during the pulse. The Q-spoiler enables the circuit to recover quickly after the pulse, and has been used in an NQR experiment to achieve a sensitivity of about 2 /times/ 10/sup 16/ nuclear Bohr magnetons in a single free precession signal with a bandwidth of 10 kHz. In a third experiment, a sample containing /sup 35/Cl nuclei was placed in a capacitor and the signal detected electrically using a tuned SQUID amplifier and Q-spoiler. In this way, the electrical polarization induced by the precessing Cl nuclear quadrupole moments was detected: this is the inverse of the Stark effect in NQR. Two experiments involving NMR have been carried out. In the first, the 30 MHz resonance in /sup 119/Sn nuclei is detected with a tuned amplifier and Q-spoiler, and a single pulse resolution of 10/sup 18/ nuclear Bohr magnetons in a bandwidth of 25 kHz has been achieved. For the second, a low frequency NMR system has been developed that uses an untuned input circuit coupled to the SQUID. The resonance in /sup 195/Pt nuclei has been observed at 55 kHz in a field of 60 gauss. 23 refs., 11 figs.

• Research Organization: Lawrence Berkeley Lab., CA (USA)
• DOE Contract Number: AC03-76SF00098
• OSTI ID: 6225439
• Report Number(s): LBL-26234; CONF-880812-42; ON: DE89007657
• Country of Publication: United States
• Language: English

Related Subjects

420201* -- Engineering-- Cryogenic Equipment & Devices
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
AMPLIFIERS
CHLORINE 35
CHLORINE ISOTOPES
DAYS LIVING RADIOISOTOPES
ELECTRONIC EQUIPMENT
EQUIPMENT
EVEN-ODD NUCLEI
FLUXMETERS
HEAVY NUCLEI
HIGH FREQUENCY AMPLIFIERS
INTERMEDIATE MASS NUCLEI
INTERNAL CONVERSION RADIOISOTOPES
ISOMERIC TRANSITION ISOTOPES
ISOTOPES
JOSEPHSON JUNCTIONS
JUNCTIONS
LIGHT NUCLEI
MAGNETIC RESONANCE
MEASURING INSTRUMENTS
MICROWAVE EQUIPMENT
NMR SPECTROMETERS
NUCLEAR MAGNETIC RESONANCE
NUCLEI
ODD-EVEN NUCLEI
PLATINUM 195
PLATINUM ISOTOPES
RADIOISOTOPES
RESONANCE
SPECTROMETERS
SQUID DEVICES
STABLE ISOTOPES
SUPERCONDUCTING DEVICES
SUPERCONDUCTING JUNCTIONS
TIN 119
TIN ISOTOPES
USES