Null-Balanced Torque Magnetometer in 60 kG with the Optical Feedback Circuit

Nariaki YAMAMOTO  Naoki KAGAWA  Kentaro KITAMURA  Daisuke TAKIGAWA  Takekazu ISHIDA  

Publication
IEICE TRANSACTIONS on Electronics   Vol.E85-C   No.3   pp.752-755
Publication Date: 2002/03/01
Online ISSN: 
DOI: 
Print ISSN: 0916-8516
Type of Manuscript: Special Section PAPER (Special Issue on Superconductive Electronics)
Category: Instruments and Coolers
Keyword: 
torque,  low temperature,  superconducting magnet,  optical sensor,  PID control,  

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Summary: 
We have designed a torque magnetometer using a 60-kG split-type superconducting magnet. A balance torque compensates the torque acting on a sample in the magnetic field. The feedback circuit for a sample direction consists of an optical position sensor, a moving coil, and a PID controller. We measured the coil current to know a sample torque. The whole torque machinery is directly rotated by a stepping motor of angular resolution 0.0036. An advantage of the torque apparatus is a wide dynamic range up to 1000 dyncm. The sample temperature can be controlled between 4 K and 300 K.