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Title: Low-frequency nuclear quadrupole resonance with a dc SQUID

Abstract

Conventional pure nuclear quadrupole resonance (NQR) is a technique well suited for the study of very large quadrupolar interactions. Numerous nuclear magnetic resonance (NMR) techniques have been developed for the study of smaller quadrupolar interactions. However, there are many nuclei which have quadrupolar interactions of intermediate strength. Quadrupolar interactions in this region have traditionally been difficult or unfeasible to detect. This work describes the development and application of a SQUID NQR technique which is capable of measuring intermediate strength quadrupolar interactions, in the range of a few hundred kilohertz to several megahertz. In this technique, a dc SQUID (Superconducting QUantum Interference Device) is used to monitor the longitudinal sample magnetization, as opposed to the transverse magnetization, as a rf field is swept in frequency. This allows the detection of low-frequency nuclear quadrupole resonances over a very wide frequency range with high sensitivity. The theory of this NQR technique is discussed and a description of the dc SQUID system is given. In the following chapters, the spectrometer is discussed along with its application to the study of samples containing half-odd-integer spin quadrupolar nuclei, in particular boron-11 and aluminum-27. The feasibility of applying this NQR technique in the study of samples containingmore » integer spin nuclei is discussed in the last chapter. 140 refs., 46 figs., 6 tabs.« less

Authors:
Publication Date:
Research Org.:
Lawrence Berkeley Lab., CA (United States)
Sponsoring Org.:
USDOE; USDOE, Washington, DC (United States)
OSTI Identifier:
5258685
Report Number(s):
LBL-31124
ON: DE92014506
DOE Contract Number:
AC03-76SF00098
Resource Type:
Technical Report
Resource Relation:
Other Information: Thesis (Ph.D)
Country of Publication:
United States
Language:
English
Subject:
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; 71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; ALUMINIUM 27; NUCLEAR QUADRUPOLE RESONANCE; BORON 11; ANALYTICAL SOLUTION; BORIC ACID; BORON NITRIDES; BORON OXIDES; HAMILTONIANS; KHZ RANGE 100-1000; NITROGEN; PETALITE; SAPPHIRE; SQUID DEVICES; TEMPERATURE RANGE 0000-0013 K; ALUMINIUM ISOTOPES; BORON COMPOUNDS; BORON ISOTOPES; CHALCOGENIDES; CORUNDUM; ELECTRONIC EQUIPMENT; ELEMENTS; EQUIPMENT; FLUXMETERS; FREQUENCY RANGE; HYDROGEN COMPOUNDS; INORGANIC ACIDS; ISOTOPES; KHZ RANGE; LIGHT NUCLEI; MATHEMATICAL OPERATORS; MEASURING INSTRUMENTS; MICROWAVE EQUIPMENT; MINERALS; NITRIDES; NITROGEN COMPOUNDS; NONMETALS; NUCLEI; ODD-EVEN NUCLEI; OXIDE MINERALS; OXIDES; OXYGEN COMPOUNDS; PNICTIDES; QUANTUM OPERATORS; RESONANCE; SILICATE MINERALS; STABLE ISOTOPES; SUPERCONDUCTING DEVICES; TEMPERATURE RANGE; 665100* - Nuclear Techniques in Condensed Matter Physics - (1992-); 661210 - Cryogenics- (1992-)

Citation Formats

Chang, J.W. Low-frequency nuclear quadrupole resonance with a dc SQUID. United States: N. p., 1991. Web. doi:10.2172/5258685.
Chang, J.W. Low-frequency nuclear quadrupole resonance with a dc SQUID. United States. doi:10.2172/5258685.
Chang, J.W. 1991. "Low-frequency nuclear quadrupole resonance with a dc SQUID". United States. doi:10.2172/5258685. https://www.osti.gov/servlets/purl/5258685.
@article{osti_5258685,
title = {Low-frequency nuclear quadrupole resonance with a dc SQUID},
author = {Chang, J.W.},
abstractNote = {Conventional pure nuclear quadrupole resonance (NQR) is a technique well suited for the study of very large quadrupolar interactions. Numerous nuclear magnetic resonance (NMR) techniques have been developed for the study of smaller quadrupolar interactions. However, there are many nuclei which have quadrupolar interactions of intermediate strength. Quadrupolar interactions in this region have traditionally been difficult or unfeasible to detect. This work describes the development and application of a SQUID NQR technique which is capable of measuring intermediate strength quadrupolar interactions, in the range of a few hundred kilohertz to several megahertz. In this technique, a dc SQUID (Superconducting QUantum Interference Device) is used to monitor the longitudinal sample magnetization, as opposed to the transverse magnetization, as a rf field is swept in frequency. This allows the detection of low-frequency nuclear quadrupole resonances over a very wide frequency range with high sensitivity. The theory of this NQR technique is discussed and a description of the dc SQUID system is given. In the following chapters, the spectrometer is discussed along with its application to the study of samples containing half-odd-integer spin quadrupolar nuclei, in particular boron-11 and aluminum-27. The feasibility of applying this NQR technique in the study of samples containing integer spin nuclei is discussed in the last chapter. 140 refs., 46 figs., 6 tabs.},
doi = {10.2172/5258685},
journal = {},
number = ,
volume = ,
place = {United States},
year = 1991,
month = 7
}

Technical Report:

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  • The high sensitivity of dc SQUID amplifiers is extended to the radio-frequency range. We perform a detailed investigation of the dynamic input impedance of tightly coupled dc SQUIDs and of the influence of parasitic capacitance between the SQUID and the input circuit on the SQUID characteristics. The reactive part of the dynamic input impedance is found to be determined by the inductive coupling, whereas the resistive part is found to be dominated by capacitive feedback. We also discuss the optimization of the input circuits for both tuned and untuned amplifiers and derive expressions for the optimum source resistance, gain andmore » noise temperature for a given frequency, input coil and coupling. The performance of the amplifiers designed according to these prescriptions is measured. The gain of an untuned amplifier operated at 100 MHz at 4.2K is 16.5 +- 0.5dB with a noise temperature of 3.8 +- 0.9K; at 1.5K the gain increases to 19.5 +- 0.5dB while the noise temperature decreases to 0.9 +- 0.4K. A tuned amplifier operated at 93 MHz and 4.2K has a gain of 18.6 +- 0.5dB and a noise temperature of 1.7 +- 0.5K. These results are in good agreement with predicted values. The usefulness of these sensitive amplifiers for the detection of magnetic resonance is demonstrated. A SQUID system for pulsed nuclear quadrupole resonance at about 30 MHz is developed. 59 refs., 31 figs., 3 tabs.« less
  • Conventional pure nuclear quadrupole resonance (NQR) is a technique well suited for the study of very large quadrupolar interactions. Numerous nuclear magnetic resonance (NMR) techniques have been developed for the study of smaller quadrupolar interactions. However, there are many nuclei which have quadrupolar interactions of intermediate strength. Quadrupolar interactions in this region have traditionally been difficult or unfeasible to detect. This work describes the development and application of a SQUID NQR technique which is capable of measuring intermediate strength quadrupolar interactions, in the range of a few hundred kilohertz to several megahertz. In this technique, a dc SQUID (Superconducting QUantummore » Interference Device) is used to monitor the longitudinal sample magnetization, as opposed to the transverse magnetization, as a rf field is swept in frequency. This allows the detection of low-frequency nuclear quadrupole resonances over a very wide frequency range with high sensitivity. The theory of this NQR technique is discussed and a description of the dc SQUID system is given. In the following chapters, the spectrometer is discussed along with its application to the study of samples containing half-odd-integer spin quadrupolar nuclei, in particular boron-11 and aluminum-27. The feasibility of applying this NQR technique in the study of samples containing integer spin nuclei is discussed in the last chapter. 140 refs., 46 figs., 6 tabs.« less
  • Conventional NMR and NQR spectrometers use transistor-based detectors, which are responsive only to voltage. This forces the experimenter to convert the sample magnetization to a voltage, a process that is less efficient at low frequencies when the Faraday induction effect is used. However, the SQUID directly measures the magnetization, so there is no frequency dependent sensitivity to the sample magnetization. Of course, many other devices also measure magnetic field directly, but none has the low frequency sensitivity of the SQUID. Chapter 2 presents the theory required to extend conventional magnetic resonance to z-axis magnetic resonance, a form most efficient formore » the SQUID. The operating principles of the SQUID, as well as the techniques used to convert the SQUID response into a useful output voltage, are outlined in Chapter 3. The SQUID spectrometer constructed for these experiments is described in Chapter 4. Also in this chapter are a discussion of the design considerations for a SQUID spectrometer, and indications of the overall performance of our instrument. Experimental results on NQR and low frequency NMR are found in Chapters 5 and 6, respectively. 96 refs., 38 figs., 5 tabs.« less
  • Radiation damage effects have been observed and measured in NaI, KI, LI, and KBr which have received reactor irradiation. The data have been used to determine the defect density in the irradiated crystals and the mean free path between displacement collisions. The results are in substantial agreement with the caiculations of Seitz and Koehler. Pre-irradiation studies of boron carbide have shown that the central ''carbon'' position in the ''threecarbon chain'' of this structure is often occupied by a boron atom. Pre-irradiation studies of boron oxide-alkali oxide glasses have uniquely determined the boron-oxygen configuration and bonding behavior as a function ofmore » the glass composition. The results offer an explanation of the thermal expansion and volume per oxygen dependence on the oxygen content of the glass. The bonding electron distributions in several metal borides and boron nitride have been determined from the effect of the B/sup 11/ electrical quadrupole coupling constant on the nuclear magnetic resonance. (See also NYO-7623.) (auth)« less
  • 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 systemmore » 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.« less