Studies on driver equivalent impedance and power transfer efficiency in the drivers of the SPIDER inductively coupled RF ion source

SPIDER ion source consistsof 8 drivers where the plasma is produced by the application of the radio frequency power to an inductive coil. The plasma inside the driver is influenced by several parameters (like RF power, gas pressure, frequency, magnetic field,etc) and mechanisms (like ohmic and stochastic heating). To understand the plasma behavior a methodology has been developed in a previous work based on input parameters, plasma heating mechanisms andanelectrical model(transformer of multi current filament model). This document highlights a further improvement and adevelopment ofthe methodology for the estimation of the driver equivalent resistance and the power transfer efficiency to the plasma generated in an inductively coupled radio frequency ion source. The improved methodology has been applied to a single driver of SPIDER ion source and the results obtained in terms of driver equivalent resistance have been validated against the first experimental results. The power transfer efficiency to the plasma is predicted to be lower than 85% at maximum RF power (~100kW).