Beam Recovery

PREX Main<< HOW TOs << Expert Tools

NEW INFORMATION For CREX

Establishing High Current on a Calcium Target

OLD INFORMATION For PREX

GOALS

• 1. Make sure we are centered on beam collimator so we don't destroy it.
• 2. Ideally that BPM position is also compatible with not hitting the copper frame of the Pb/D target. Need to check.
• 3. Rastered beam should be big enough to spread heat and not melt the target, and also at least 3 mm from copper frame. (scatter from Cu would be a ruinous background.)

NOTE

• The "MCC units" of raster is what they set and what is displayed in the Raster GUI.
• The "observed" raster size is what is displayed by spot_L. It's different because of quad optics.
• Make sure you understand the difference. We care about the observed size, but we communicate to MCC by telling them in their units.

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 P. (If someone has turned off HRS magnets they may not come back in right state.)

Image 1 - 1H quad settings

Image 2

1. Check if the 1H quads have changed - correct values are in halog 3708676
2. See this log entry for more information on which quads to check before moving forward: halog 3779853
3. Empty target, establish correct beam position Check beam position
   • BPM4A (X,Y) = ( 0, 0) mm
   • BPM4E (X,Y) = ( 0.6, 0.4) mm
   • See white board for updates on these.
4. Establish Raster (12 width and 7.2 height in MCC units)
   • It gets turned off for access, (sometimes people forget)
   • Still at empty target.
   • All scint HV off (normally they are).
5. Put in Carbon Hole (90 deg) target
   • 1 uA rastered beam on Carbon Hole target.
   • Lock the beam position using 1 uA current.
   • Go to 20 nA current
   • Keep an eye 1H04B, D to watch for changes during the low current running
   • Turn on scintillator HVs (S0A,B and S3 in each arm) - check T1 rates (~50-100 kHz) and reduce beam current if necessary
   • record attenuator and slit value
   • Check spot++ on Carbon hole target (see halog 3707033???)
     • Is the hole within 1mm of center of the raster in the horizontal direction?
     • Is the size of the raster about 4x6 mm2 (2mm diameter hole) in the plot?
6. Turn off all scint HV.
7. Put in the Lead target
   • See white board for which one we are using
   • IMPORTANT: Raster always on and 12x7.2 mm2 (MCC unit) when Lead target in beam !!
8. Ready for high current: Ramp up to desired current 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 12x7.2 mm2 (MCC unit) when Lead / 1% carbon 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 1 uA
   • Do a spot_L run with ps8=2 as explained above.
4. Put in Pb/1% Carbon Target
   • See white board for which one.
5. Ask for 1 uA. Check beam positions.
   • BPM4A (X,Y) = ( 0, 0) mm
   • BPM4E (X,Y) = ( 0.6, 0.4) 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.
   • Increase raster by 50% and check spot++ again to make sure not hitting the frame
   • Go back to 12x7.2 mm2 (MCC unit) raster size.
7. Ready for high current: Ramp up to 50 uA at about 10 uA per min.