A HIGH PRECISION, PuLsn, MAGNETIC FIEIl) GENERATOR:

This paper describes a repetitively pulsed, magnetic field modulator which is capable of producing fast rise time, flat top current pulses into a Helmholtz style coil of approximately 20 microhenries inductance. The modulator utilizes a hydrogen thyratron and a 25 nanofarad capacitor for the fast rise (approximately 1 microsecond) portion of the current pulse, while a low voltage, low impedance (0.2 ohm) PFN is used in conjunction with a high voltage blocking diode to sustain the current in the coil. Energy is recycled so that all of the PFN's energy comes from that which is stored in the 25 nanofarad capacitor. A single, high voltage power supply is, therefore, all that is required to power the system. The precision of the current output is such that, for a current of 500 amps, less than 6% variation in output is measured for greater than 30 microseconds. At 700 amps output, the variation in current is 2 %, while pulse-topulse variations are less than 1 %. The maximum repetition rate of the system, which is mainly limited by energy recycling times, is approximately 2500 pulses per second.