Redesign of the Analysing Magnet in the ISISIT Penning Ion Source

摘要

A full 3D electromagnetic finite element analysis and particle tracking study isundertaken of the ISIS Penning surface plasma H ion source. The extraction electrode, 90°analysing magnet, post-extraction acceleration gap and 700 mm of drift space have beenmodelled in CST Particle Studio 2008 to study the beam acceleration and transport at all pointsin the system. The analyzing magnet is found to have a sub-optimal field index, causing beamdivergence and contributing the beam loss. Different magnet pole piece geometries are modelledand the effects of space charge investigated. The best design for the analysing magnet involves ashallower intersection angle and larger separation of the pole faces. This provides radial focusingto the beam, leading to less collimation. Three new sets of magnet poles are manufactured andtested on the Ion Source Development Rig to compare with predictions.