Nuclear magnetic resonance with dc SQUID preamplifiers

Conference · Wed Mar 01 00:00:00 EST 1989 · IEEE Trans. Magn.; (United States)

OSTI ID:5918462

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

Sensitive radio-frequency (rf) amplifiers based on dc Superconducting QUantum Intererference Devices (SQUIDSs) 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 x 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.

• Research Organization: Dept. of Physics, Univ. of California, and Materials and Chemical Sciences Div., Lawrence Berkeley Lab., Berkeley, CA (US); Dept. of Physics, Univ. of California, Berkeley, CA (US); Dept. of Chemistry, Univ. of California, and Materials and Chemical Sciences Div., Lawrence Berkeley Lab., Berkeley, CA (US)
• OSTI ID: 5918462
• Report Number(s): CONF-880812-
• Journal Information: IEEE Trans. Magn.; (United States), Vol. 25:2; Conference: Applied superconductivity conference, San Francisco, CA, USA, 21 Aug 1988
• Country of Publication: United States
• Language: English

Related Subjects

71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
SQUID DEVICES
DESIGN
AMPLIFIERS
CHLORINE 35
EXPERIMENTAL DATA
JOSEPHSON JUNCTIONS
NOISE
NUCLEAR MAGNETIC RESONANCE
NUCLEAR QUADRUPOLE RESONANCE
RF SYSTEMS
CHLORINE ISOTOPES
DATA
ELECTRONIC EQUIPMENT
EQUIPMENT
FLUXMETERS
INFORMATION
ISOTOPES
JUNCTIONS
LIGHT NUCLEI
MAGNETIC RESONANCE
MEASURING INSTRUMENTS
MICROWAVE EQUIPMENT
NUCLEI
NUMERICAL DATA
ODD-EVEN NUCLEI
RESONANCE
STABLE ISOTOPES
SUPERCONDUCTING DEVICES
SUPERCONDUCTING JUNCTIONS
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656001 - Condensed Matter Physics- Solid-State Plasma