Study of RF Stray Currents in ITER Neutral Beam Test Facilities

The operation of SPIDER (Source for the Production Ions Deuterium Extracted from Radio-frequency plasma), full-scale prototype ITER NBI (Neutral Beam Injector) radio-frequency ion source, pointed out deleterious effects caused by stray Radio-Frequency (RF) currents flowing in electrical equipment not included RF power system. MITICA (Megavolt Injector and Concept Advancement), NBI, is characterized a similar design terms layout supplies connections to beam source; thus, it expected be subject problem. system composed four generators, coaxial lines loads. Each generator rated at 200 kW frequency range 0.9 ÷ 1.1 MHz. delivered loads via as many lines, housed inside multiconductor transmission line. load consists capacitive matching network two plasma drivers series. Due presence beam-source side (e.g., parasitic capacitances), unwanted can flow through alternative paths negatively affect components intended power, output stages several diagnostics installed High-Voltage Deck (HVD) source. This paper presents development circuital model used estimate system; understanding this phenomenon with predictive capabilities fundamental assessment performance both and, general, layouts respect issue.