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George Nevard

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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.