Design Specification, Theory of Operation, and Preliminary Results for a 'Thermistor Probe' to Measure Synchrocyclotron Internal Beam Current and Results for the Nevis Synchrocyclotron Internal Proton Current

摘要

This paper is in three parts. The first part deals with a 'thermistor probe' which was developed and used to evaluate the internal proton current (time-average counting each proton just once) vs radius in the Nevis Synchrocyclotron. The method consists of measuring the heating produced in a 1/8-in. thick tungsten plate. The choice of material and thickness was a compromise which attempted to provide enough multiple scattering on one traversal to minimize the probability of subsequent traversals, while remaining sufficiently thin to minimize the chance that the protons would leave the end of the plate before stopping or completing one traversal. The paper describes the probe and the measurements and their analysis. Part II describes the central region of the cyclotron and improvements made since September 1965 which have led to a factor of between two and four increase in the proton current. One change was to increase central region magnetic vertical focusing. The other main change was to develop and use a zirconium cold cathode pulsed ion source. Part III presents a comparison with available information on other synchrocyclotrons, emphasizing the internal proton currents. (Author)