The SNS machine protection system: Early commissioning results and future plans

The Spallation Neutron Source under construction in Oak Ridge TN has commissioned low power beam up to 187 MeV. The number of MPS inputs is about 20% of the final number envisioned. Start-up problems, including noise and false trips, have largely been overcome by replacing copper with fiber and adding filters as required. Initial recovery time from Machine Protection System (MPS) trips was slow due to a hierarchy of latched inputs in the system: at the device level, at the MPS input layer, and at the operator interface level. By reprogramming the MPS FPGA such that all resets were at the input devices, MPS availability improved to acceptable levels. For early commissioning MPS inputs will be limited to beam line devices that will prohibit beam operation. For later operation, the number of MPS inputs will increase as both software alarms and less intrusive MPS inputs such as steering magnets are implemented. Two upgrades to SNS are on the horizon: a 4 MW upgrade and a second target station. Although these are years away the MPS system as designed should easily accommodate the increase in power and pulse-to-pulse target switching at 120 Hz.