Abstract
The Spallation Neutron Source at Oak Ridge National Laboratory is ramping up the accelerated
proton beam power to 1.4 MW and just reached 1 MW. The rf-driven multicusp ion source that
originates from the Lawrence Berkeley National Laboratory has been delivering 38 mA H− beam
in the linac at 60 Hz, 0.9 ms. To improve availability, a rf-driven external antenna multicusp ion
source with a water-cooled ceramic aluminum nitride AlN plasma chamber is developed.
Computer modeling and simulations have been made to analyze and optimize the rf performance of
the new ion source. Operational statistics and test runs with up to 56 mA medium energy beam
transport beam current identify the 2 MHz rf system as a limiting factor in the system availability
and beam production. Plasma ignition system is under development by using a separate 13 MHz
system. To improve the availability of the rf power system with easier maintenance, we tested a 70
kV isolation transformer for the 80 kW, 6% duty cycle 2 MHz amplifier to power the ion source
from a grounded solid-state amplifier. © 2010 American Institute of Physics.
