Developments for Performance Improvement of SNS H- Ion Source RF Systems

The Spallation Neutron Source (SNS) at Oak Ridge National Laboratory is ramping up the accelerated proton beam power to 1.4 MW after achieving 1.1 MW. The RFdriven multicusp ion source employing internal RF antenna originally developed by LBNL has been used to deliver up to ~38 mA H beam current in 1 msec pulses at 60 Hz with limited availability. To improve availability, an RF-driven external antenna multicusp ion source with a water-cooled, ceramic aluminum nitride (AlN) plasma chamber has been developed. Computer simulations were done to analyze and optimize the RF performance of the new design. Plasma ignition system using a separate 13 MHz antenna is under development. To improve the RF power system for easier maintenance, a 70-kV isolation transformer for the 80-kW, 6% duty cycle 2-MHz amplifier was developed and used to power the ion source from a grounded power amplifier.