Current and field stabilization of the 9-kw Electromagnet of the A.E.I. Magnetic Spectrograph

The current stabilized power supply for energizing the electromagnet provides variation of magnet current over the range 20-200A, corresponding to a magnetic field in the gap of the electromagnet of approximately 2,000-16,000 oersteds. The d.c. generator, which supplies power to the magnet, is converted into a low noise, high power, wideband amplifier which can be incorporated into the current stabilizing loop without excessive phase shifts. The current in the magnet is regulated by comparing the voltage drop across a standard resistance, in series with the magnet, with a reference voltage which can be checked against a standard cell. The error voltage is amplified and used to control the field current of the generator. The magnet current is regulated to ± 0·01 per cent. and the resultant magnetic field is measured by a nuclear magnetic resonance fluxmeter to an overall accuracy of ± 0·05 per cent. Precision field stabilization is achieved by using the signals obtained from nuclear resonance equipment to control the output current of the generator. Using this system the magnetic field of the spectrograph is controlled to an accuracy of ± 0·01 per cent.