TFTR Neutral Beam Magnet Analysis

In running TFTR, a desire to improve its capabilities naturally arises. One improvement under consideration is to increase the neutral beam pulse length thereby increasing plasma heating. One of the steps in achieving this is to reduce the heating of the ion dump collector plate by spreading out the neutral beam injector's ion beam impinging on it (Fig. 1). Finding an efficient way of doing this is the subject of the analysis described in this paper. The analysis consists of two major parts. One part, performed at MIT, covers the magnetic performance of the ion dump magnets. The second part, performed at Princeton, covers the particle trajectories and consequent spread patterns of the ion beams on the collector plates. This paper includes a description of the development of the computer models of the magnet, and a comparison of calculated and measured magnetic fields. A description of the approach for analysis of the particle trajectories is given, followed by a comparison of calculated trajectories with measured data. A discussion of the results of analyzing the performance of various alternate magnet configurations is included, followed by a qualitative analysis and discussion relating the numerically determined performance of the various magnet configurations to the basic design parameters in a fundamental manner.