Precision High Speed Current Regulators for Occasionally Switched Inductive Loads

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Abstract
Power supplies used in field‐cycling nuclear resonance experiments are described. These are used to switch an air coil from high field to low field as rapidly as possible, then back to high field after a short time. This sequence must be repeated every few seconds or minutes. An example of a simple regulator is described, and methods of output switching with relays are discussed. A circuit is described which delivers up to 10 kG (15 A) in a 2.6 cm i.d. superconducting coil with a switching speed of 5×105 G/sec and an accuracy probably as great as 1 G. Speed is achieved by automatic connection, during up or down switching, of energy storage capacitors across the magnet, operating at much higher voltage than the steady‐state voltage level across the magnet and pass transistors.