1. ISIS Beam Protection System and MICE operation. Dean Adams 29 Nov 07 Presented by Chris Rogers

2. ISIS Beam Protection System ISIS Beam Protection System (BPS) consists of hardware interlocks (magnets, RF..) and beam diagnostic measurements (Intensity and Beam loss monitors). The latter using DAQ and tolerance comparison to determine trips. To minimise beam off time an ‘inhibit unit’ sits above the BPS system and turns the beam off on a BPS trip for ~ 1.5 s and then automatically switches the beam back on. If another BPS trip occurs within 10s then the beam is switched off by insertion of a beam stop. This then requires a manual reset to enable beam.

3. Beam Intensity Monitors 1 Current transformer (R5IM1) sits in SP5. DAQ resolution 2e10 protons per pulse. Acceleration tolerances 2.5 – 9.8 ms BPS trip : 3 consecutive > 2e12 each 25 consecutive > 0.5e12 average/pulse BPS warning displayed in ISIS MCR @ 30 s and 20 mins if average per pulse > 0.25e12 or 0.2e12

4. Beam Loss Monitors 39 BLM’s in ring. Each BLM signal is integrated 0-10 ms and compared to a tolerance. Trip issued when 20 pulses > tolerance in 15 MINUTES. Pulse count reset on each trip. BLM upgrade Jan 08. Pulse count changed to 20 CONSECUTIVE pulses.

5. MICE operation and the current ISIS BPS Assumptions: MICE at 1 Hz, ISIS at 50 Hz. Intensity Monitors 3 consecutive pulses : MICE cannot force this trip alone. 25 pulse average : MICE could produce one BPS trip if it intercepted more than 25* 0.5e12 = 1.25e13. This would produce an inhibit. The next MICE dip occurs in less than the 10s inhibit window so additional loss would cause another trip and turn the machine off. Beam Loss Monitors 20 pulses in 15 mins : MICE can inhibit but never trip 20 consecutive pulses: MICE cant inhibit or trip.

6. Where to go next. Old HEP target operated @50 Hz diping at 7 ms for ~ 200 µs. ISIS BLM tolerances were 0.2 V in super period 7. MICE target @1Hz but dips from 8-10 ms. Different machine activation source. Need to quantify.. Current BPS protection not suitable for MICE. ISIS will need to produce some new trip mechanism on the BLM’s. Ie DAQ system measuring SP7 losses at 1 Hz connected to ISIS BPS system. Target tests in Jan 08 should limit loss to 0.05 V trip level. During this time machine activation can be measured. The requirement for MICE rates and ISIS activation can then be reviewed.