Beam Recovery

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PREX Main<< HOW TOs << Expert Tools

PREX I procedure

• Harp scans
• Bullseye scans

Procedure for Long Beam Down

Check if the septum on !!

• (It gets turned off for access, sometimes people forget.)
• Ask MCC to set septum magnet

Make sure we have Tune B. (If someone has turned off HRS magnets they may not come back in right state.)

1. Empty target, establish correct beam position Check beam position
   • 5 uA empty target
   • BPM4A (X,Y) = ( 0, 0) mm
   • BPM4B (X,Y) = ( 0, +1) mm
   • See white board for updates on these.
   • Tolerances on these : +/- 0.3 mm
2. Establish Raster
   • It gets turned off for access, sometimes people forget.)
   • Still at empty target.
   • All scint HV off (normally they are).
   • Need to use T8 pulser, so use ps8 = 2 on L-HRS.
   • spot_L check of raster, see 6x4 mm2 on target
3. Put in BeO target, for visual check of spot (if camera still works)
   • 10 uA rastered beam on BeO.
   • May need to request MCC for rapid beam-on / beam-off to see spot.
   • "Rapid" can be done by turning on/off laser at polarized source.
4. Establish 5 nA
   • Still with BeO target
   • Ask MCC for Laser Attenuator = 65 and Slit = 15. (This might need to change)
   • These two knobs (atten and slit) can reduce current to nA range.
   • Turn on L-HRS upper scintillator paddle HV which makes trigger T5.
   • Card 2, chan 10, HV = -1400 V
   • Should observe T5 = 2000 Hz +/- 1000. Adjust atten, slit if necessary.
5. Put in the Lead / Diamond target
   • See white board for which one we are using
   • As I write this, we're using number 2 (middle).
   • IMPORTANT: Raster always on and 6x4 when Lead / Diamond target in beam !!
   • Ask for the SAME attenuator and slit as above.
   • Observe T5 = 13 +/- 3 kHz. This is fine.
6. Run spot_L again, this time with ps8=65535 and ps5=10
   • Observe the raster current pattern, see if it's flat
   • Flat means we're not hitting a frame !
   • Gentle slope due in X is presumably form factor (don't worry)
   • For reference, see halog 314132
7. Turn off all scint HV.
8. Ready for high current: Ramp up to 50 uA at about 10 uA per min.

Procedure for Short Beam Down or target movement

less than 2 hours of no beam, and no changes to beam

IMPORTANT: Raster always on and 6x4 mm (observed on target) when Lead / Diamond target in beam !!

1. If you are unsure of raster status, check it !!
2. Can be sure raster is ok if
   • You were just running and it was on.
   • Check the scope in middle room (familiar TV pattern of raster)
   • Look at raster EPICS screen.
3. To check raster:
   • Go to empty target
   • Ask for 5 uA
   • Do a spot_L run with ps8=2 as explained above.
4. Put in Pb/Diamond Target
   • See white board for which one.
   • As I write this, we are using number 2 (middle)
5. Ask for 5 uA. Check beam positions.
   • BPM4A (X,Y) = ( 0, 0) mm
   • BPM4B (X,Y) = ( 0, +1) mm
   • See white board for updates on these.
   • Tolerances on these : +/- 0.3 mm
6. If you didn't do spot_L in the first step, do one a quick one now.
   • Want 6x4 mm on target.
7. Ready for high current: Ramp up to 50 uA at about 10 uA per min.