Beam Pulse Selector for a Sector Focused Cyclotron

For the U. S. Naval Radiological Defense Laboratory's (NRDL) 70-inch sector-focused cyclotron a beam-pulse selector system has been developed by means of which an individual beam pulse or "fish" can be selected near the center of the machine and then accelerated to full energy and extraction. The beam is normally deflected axially into a beam stopper by a negative dc voltage of 10.5 kV applied to the deflector plates via a helically wound coaxial line of 2000 ohms characteristic impedance. An individual fish is transmitted by applying a 5.5 kV positive pulse of less than 40 nsec duration at the input of the coaxial line.