| Summary: | 碩士 === 淡江大學 === 物理學系 === 86 === Ac magnetic susceptibility measurements are widely used for
sample characterization in material study . Since the magnetic
properties of the entire sample can be revealed in the
measurements , it is very important for superconducting studies.
The ac susceptibility measuring system includes a CRYOSTAT and a
coil detection device . The coil detection device consists of a
primary coil and secondary coils . Primary coil supplies an ac
magnetic field H which would induce magnetization in the sample
. It will then result in a signal of the secondary coils given
by χac = dM / dH . Therefore the temperature dependent χac
can be determined. Unsatisfactory results were obtained in using
our ac magnetic susceptibility system bought from U.S.A. .
Many defects were found. For example, (1) the accuracy of χac
is not acceptable , (2) the arrangement of the temperature
sensor need to be readjusted , (3) each measurement takesup to
10 hours, (4) the lowest working temperature of the system is
39K . A new design for CRYOSTAT has been carried out since most
of the defects were found to be due to the improper design of
original CRYOSTAT. The previous problems have been improved.
Satisfactory results have been achieved and demonstrated in a
series of measurements.
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