Design of the Radiofrequency System for the 184-Inch Cyclotron

Abstract

A description is given of the frequency‐modulated oscillator and its associated r‐f circuits, as used in the 184‐inch cyclotron for accelerating deuterons to 190 million volts or alpha‐particles to 380 million volts. A 9C21 water cooled tube is used in a grounded‐grid circuit, which is tightly coupled to the single‐dee resonant circuit so that the oscillator follows the frequency of the dee over the wide range required. During normal operation the oscillator delivers approximately 20 kw of r‐f power to the dee system at an efficiency of 60 percent, giving 20 kv at the front of the dee, although the oscillator is capable of considerably more output. The frequency is swept from 12.5 mc to 9.0 mc approximately 100 times per second by a rotating condenser connected to the dee by a half‐wave transmission line. Much of the history of the design, and reasons for choices made, are given, as it is felt this may be useful to others designing frequency‐modulated oscillators for cyclotrons.