Method and apparatus for using stochastic excitation and a superconducting quantum interference device (SAUID) to perform wideband frequency response measurements
First Claim
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1. A method for obtaining wideband frequency response measurements from a sample, the method comprising the steps of:
- applying to the sample a stochastic magnetic excitation field whereby the frequency components of the excitation field which coincide with the resonant frequencies of the nuclear magnetic moments in the staple generate an oscillating magnetic field in and around the sample;
sensing the oscillating magnetic field around the sample by means of the current induced in a detection coil closely adjacent to the sample;
coupling the sensed oscillating current to a SQUID by means of a superconducting input coil in a SQUID sensor; and
providing the SQUID output signals, which include the characteristic frequency responses from the sample in a superconductive modulation coil, to measurement and analysis apparatus to thereby obtain the frequency response measurements.
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Abstract
A stochastic excitation, SQUID detection system for determining the frequency response of a sample. A pair of counterwound detection coils are adjacent to an excitation coil. The sample is selectively placed in one of the detection coils for taking measurements. The SQUID sensor is a broadband, high sensitivity device which enables the frequency response of the sample to be determined over a wide bandwidth with a single measurement.
115 Citations
15 Claims
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1. A method for obtaining wideband frequency response measurements from a sample, the method comprising the steps of:
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applying to the sample a stochastic magnetic excitation field whereby the frequency components of the excitation field which coincide with the resonant frequencies of the nuclear magnetic moments in the staple generate an oscillating magnetic field in and around the sample; sensing the oscillating magnetic field around the sample by means of the current induced in a detection coil closely adjacent to the sample; coupling the sensed oscillating current to a SQUID by means of a superconducting input coil in a SQUID sensor; and providing the SQUID output signals, which include the characteristic frequency responses from the sample in a superconductive modulation coil, to measurement and analysis apparatus to thereby obtain the frequency response measurements. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. Apparatus for obtaining frequency response measurements from a sample, said apparatus comprising:
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a stochastic signal source; an excitation coil connected to said stochastic signal source, the sample being positioned with respect to said excitation coil so that the magnetic field of said excitation coil is applied to the sample, thereby causing the sample to generate an oscillating magnetic field; detection coil means adjacent to the sample such that the oscillating magnetic field from the sample inductively couples to said detection coil, thereby causing currents to flow in said detection coil; a superconducting input coil connected to said detection coil means such that the currents flowing in said detection coil also flow in said input coil; and a SQUID sensor, said input coil being coupled to said SQUID sensor such that the currents flowing in said input coil cause said SQUID sensor to generate an output voltage where the frequency response of the sample is contained in the oscillating output voltage. - View Dependent Claims (10, 11, 12, 13, 14, 15)
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Specification