Highly Stabilized Power Supply for Spectrometer

The two 4000A, 150V power supplies for the spectrometer magnet of the Bates Linac have a current regulation and stability of better than .001% for an 8-hour period. Current sensing is accomplished by a 5-volt precision shunt. The output is programmed by a stable dc voltage reference with a 6-digit keyboard. The rate of current increase or decrease for controlling magnet excitation is adjustable up to a rate of 4000A per minute. Power dissipation in the 300 pass transistors of each supply is limited by automatically controlling the emitter to collector voltage with the use of a variable voltage transformer. To avoid possible conducted or radiated interference with experimental signals, no silicon-controlled rectifiers are used. The major portion of this article is devoted to an analysis of the stability.