Lake Shore Cryotronics, Inc.

John K Krause

Bradley C Dodrill

Victor Wang

Edward C Maloof

David Plaga

Jefferey Lindemuth

A vibrating sample magnetometer controls an electromechanical drive using both ac and dc control and a position sensor. Absolute position sensing is used in a feedback loop to control both an alternating current (ac) drive and a direct current (dc) drive to the electromechanical drive. Improved performance and stability results.

Electromechanical drive for magnetometers

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

John K Krause