ISIS Beam Protection System and MICE operation.

Dean Adams

29 Nov 07

Presented by Chris Rogers

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.

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

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.

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.

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.