  Internal continuous discharge can rapidly damage high-current ion sources and
their extraction systems composed of several electrodes at high voltage. To
prevent this continuous discharge inside the extraction system, a rapid
prototype using an Experimental Physics and Industrial Control System (EPICS)
software system for data acquisition has been implemented. During commissioning
of the 140 mA deuterium electron cyclotron resonance ion source of the Linear
IFMIF Prototype Accelerator (LIPAc), discharges were often observed during
plasma tuning of the ion source and beam optics tuning of the extraction
system. If such continuous discharge can be avoided, discharge-related damage
such as melting electrode edges and holes in the boron nitride disk in the ion
source can be minimized and thus an efficient machine operation can be
achieved. A veto signal is output to the machine protection system, which is
then in charge of the RF power shutdown of the ion source for a pre-determined
time. The average reaction time of this system has been measured and is about
10 ms from discharge detection to RF power shutdown of the ion source with a 50
Hz sampling frequency. This is hundreds of times slower than hardware-based
implementation. However, it prevents almost all continuous discharges at the
LIPAc ion source and extraction system, and is still much faster than an
operator's reaction time.
