Conceptual design and circuit analyses for the power supplies of the NIO1 experiment

The NIO1 (Negative Ion Optimization phase 1) experiment, whose construction has started in 2010 at Consorzio RFX in Padova in collaboration with INFN-LNL, is a radio frequency Hydrogen negative ion source designed to produce a beam current of 130 mA with 60 keV particle energy. The aim of the experiment is to provide a highly flexible system to test material properties of source components and to benchmark simulation codes for beam optics and plasma behavior. The paper focuses on a conceptual design for NIO1 power supply system on the basis of given operational and performance requirements. The requested ratings fall well within those of products available on the market and the design includes standard commercial solutions for the individual power supplies. The ion source operates at -60 kV with respect to ground, leading to a number of design issues at system level and related to mutual connection between power supplies and load, layout and grounding. These aspects, along with the crucial point of ensuring protection to the arc prone beam source, are reviewed and discussed. The study leads to a scheme integrating high voltage power supplies, high current power supplies and a possible solution for passive protection components at the power supply output.