Lake Shore Cryotronics, Inc.

Bradley C Dodrill

John K Krause

Victor Wang

A coil arrangement having a primary and two balanced secondaries is used to measure ac susceptibility and, using sample movement, also to perform absolute dc moment measurements. Since the same coil arrangement is used for both AC and DC measurements, the measurements can be made successively within a cryogenic chamber without removing the sample. This is a big advantage, because the changed conditions associated with removing and replacing a sample between measurements can cause confusing, uncorrelated results. A high speed voltmeter is used to perform the signal analysis for the moment measurement. The system can be configured to yield high resolution dc moment measurements to 25 ppm and sensitivities to better than 5.times.10.sup.-5 emu.

Magnetic property characterization system employing a single sensing

A sensing coil arrangement including a pair of sensing coils connected in opposition is used to measure AC susceptibility and, using sample movement and a DC magnetization field source, also to sense signals for absolute DC moment measurements. Since the same sensing coil arrangement is used for both AC and DC measurements, the measurements can be made successively in situ without removing the sample from a sample space (e.g., within a cryogenic chamber). This is a big advantage, because the changed conditions associated with removing and replacing a sample between measurements can cause confusing, uncorrelated results. A high speed voltmeter is used to perform the signal analysis for the moment measurement. The system can be configured to yield high resolution DC moment measurements to 25 ppm and sensitivities to better than 5.times.10.sup.-5 emu.

A thermometer is described having a broad voltage-temperature characteristic rendering it useful in making temperature measurements from below 1.degree. K. to above 500.degree. K. The thermometer employs a gallium aluminum arsenide diode and displays improved sensitivity over more conventional diode devices. In addition to providing for improved polynomial fitting for calibration curve purposes, the diode also exhibits an advantageously low magnetic field dependence.

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Westerville, OH, United States of America

Bradley C Dodrill