Practical Design Considerations For Parallel Plate Energy Analyzers With Shaped Electrodes

As the development of a parallel plate energy analyzer with a shaped electrode progresses, aspects of the simulation model become limited by practical design considerations. Construction materials, fabrication procedures, and expense dictate modifications to the optimized design. An iterative process then begins in which these realistic features are incorporated into the model, with the resulting simulation indicating changes in geometry. These changes must then be looked at from a construction standpoint and further alterations included. The results of several such design processes are presented and the implications of the modifications in terms of electric field uniformity are evaluated. The first device examined is the 400 kV analyzer to be used with the 2 Me V Heavy Ion Beam Probe (HIBP) being installed on TEXT-Upgrade. Analyzer features such as dielectric supports, voltage feedthroughs and access ports are added to the model. Also changes due to size constraints and connection to the tokamak are incorporated. Perturubation of the electric field due to these features are presented as contours of equal error within the analyzer region. The effects of these errors on the analyzer performance are evaluated. The second device explored is the 100 kV analyzer which has been in use with the 500 kV HIBP on TEXT. This analyzer is being changed from the current guard ring configuration to a shaped electrode geometry. A comparison of the electric field structure before and after modification is made. In order to use the existing analyzer vacuum chamber, a fixed boundary condiction must be imposed. This condition and the effect on the shaped electrode field structure is investigated.