Analysis of the Effect Environmental Temperature Change has on the
magnetic field Strength of Permanent Magnet Assemblies Using
Experimental Methods
Abstract
This paper aims to establish the exact relationship between Gauss Level
and Temperature for a permanent magnet assembly. Magnetrons require a
magnetic field to constrain the thermo-electrons emitted from the
cathode to form a space charge cloud. The thermo-electrons would simply
dissipate at the earth plane rather than form a space charge cloud
without this magnetic field. Hence, to ensure optimum performance and
consistency of the magnetron, the magnetic field must be calibrated. To
calibrate the magnetic field, electromagnets are commonly used as they
are highly flexible but they create additional variables such as cost
and complexity. After thorough checks to ensure they have the right
magnetic field strength, alternative approach is to use permanent
magnets. There is some difficulty is measuring field strength accurately
using permanent magnets as they are subject to environmental factors
such as temperature which affect their magnetic properties. There is the
need to compensate for these environmental factors during measurement to
ensure accuracy and therefore correct running of a magnetron. Test data
was generated through an experiment which was carried out on a permanent
magnet sample cycled in temperature while the magnetic field was
measured at periodic intervals. A mathematical model generated from test
data can then be used for compensation. The Gauss probe used to measure
magnetic field was temperature cycled independently to determine the
measurement error and a calibration magnet was cycled to validate the
data collected in the first experiment.