SNS beam chopping and its implications for machine protection

The SNS front end includes a high speed chopping system, which has the primary purpose of creating the 250 ns beam gaps essential for safe ring kicker operation. This system is also predicted to be capable of extinguishing the beam completely, and holding it off indefinitely, without damaging or activating any hardware, and without even changing the thermal equilibrium of any RF gear. It is, however, an intrinsically non-fail-safe approach to blanking an H/sup -/ beam of up to 2 MW average power. This paper will describe the front end chopping process, and the interlock systems that may allow it to be used as a convenient initial mechanism for on-demand beam blanking. It will also describe the instrumentation that can detect faults and initiate slower, more reliable, but operationally less desirable means of turning off the beam.