The central region of the Delft 12 MeV isochronous cyclotron

Abstract

In the Delft isochronous cyclotron two regions may be distinguished with respect to trajectory calculations: firstly, a main region characterized by an intricate magnetic field, a simple electric field and negligible space charge; secondly, a central region where things are just reversed. For the central region of this cyclotron two computer programmes have been written without taking space charge into account. In the first programme the trajectories in the median plane are calculated for various source-puller situations and for various initial positions and start phases. In the second programme the vertical motion is calculated for any trajectory computed in the first programme. In both programmes the equations of motion are solved by means of a fourth order Runge-Kutta procedure. The field data in the equations of motion are obtained from electrolytic tank measurements. Absence of a central magnetic field cone is the only particular supposition made, so application of the results to some other machines will probably be possible. Two typical results are: 1. 1. a beam quality of 54 mm · mrad at 12 MeV for a source hole diameter of 2 mm and a symmetrical electric field; 2. 2. a better steadiness of the centre of curvature for a more symmetrical electric field.