Sweep system design for a heavy ion beam probe on Madison Symmetric Torus

Abstract

The sweep system for the heavy ion beam probe on the Madison Symmetric Torus (MST) is described. The two components of the system are the primary sweep optics and secondary collimation plates. Key issues in the sweep system design are the small entrance and exit ports available on MST, the significant toroidal beam motion induced by the strong poloidal magnetic field, and the excessive current loading due to plasma and ultraviolet (UV). The design accommodates these issues using a crossover sweep plate design in two dimensions for the primary beam as well as two dimensional sweeping on the secondary beam. The primary beam sweep design results in a sweep range of ±20° in one direction and ±5° in the perpendicular direction. The secondary beam sweep design results in entrance angles to the energy analyzer of <3° in radial and ∼0° in toroidal directions. The procedure for calculating sweep performance including fringe fields, a system for active trajectory control, and initial experiments on plasma and UV loading are also discussed.