Tevatron Startup after 2007 Shutdown

 

Although there were no upgrade projects for the Tevatron this shutdown requiring hardware changes, the Tevatron will be starting up with operation differences that will dictate a startup progression to get back to operations efficiently. 

 

A shift startup schedule will run from 10/15/07 through 11/3/07, but hopefully we will not need to man that many shifts.

 

Changes to Tevatron operations that need to be considered during startup:

New Collision Helix - In the past, the horizontal collision helix polarity was fixed by the need of the FPD portion of the D0 experiment.  The polarity of the injection helix was fixed by the need to have Pbars on the radial outside in the F0 Lambertson for injection.  These two constraints necessitated a polarity switch of the B17 separator when transitioning from the injection to the collision helix.  This polarity change caused the beams to pass through each other with minimal separation during the transition, and this has always been a source of particle loss.  The D0 FPDs have been removed, so this constraint is no longer an issue.  During this startup, we will change the polarity of the vertical injection helix, and the polarity of both planes in the short arc of the collision helix.  Changing the polarity of the short arc collision helix alone would be sufficient to eliminate the unwanted separator polarity switch in the squeeze.  However, by changing only the horizontal plane, we lose the ability to run on the collision helix with separator two bumps at both IPs to keep the beam separated until collisions are desired.  Flipping the polarity of the vertical helix in the short arc restores this ability of doing separator two bumps at both IPs, but requires a vertical separator polarity switch to go from the original injection helix to the new collision helix.  This is precisely the problem that we were trying to solve in the other plane.  Switching the polarity of the vertical injection helix eliminates the need for the vertical polarity flip during the squeeze.

Edited Sequencer - The actual sequences for the collider mode of the sequencer were written in the last century and incremental changes have been added on.  The sequences have become inefficient, so there have been some major edits during this shutdown to clean things up. 

Orbit smoothing mechanics - The way we smoothed orbits between stores required the building and restoring of DFG files during shot setup.  A more robust method of loading tables will be implemented this startup where the corrected tables are loaded on the cards and then made active on clock event between stores.

Low Beta Quad realignment - Once again, the Low Beta Quads at both IPs have been moved to reduce corrector strength and move the collision point in a direction desired by the collider detector groups.  New orbits will need to be established.

Both TCHROM and TEVCOL OACs have been replaced by Java versions. 

VT903 was replaced by a magnet of different strength.  This will effect all programs used for closure of beam in the A1 line.

Before Beam Checklist

New C49 file - 1

Orbit Correction pieces in place -

 

Beam Startup

Establish injection and 150 GeV coasting beam -

  1. Check P1 line BPMs with low intensity and ILAM off. (I think I39 file 267 should be good.)
  2. Compare first turn to T39 file 637
  3. Compare injection display frame to T39 file 638.
  4. Make sure reverse injection works early to be sure new Helix is OK.
  5. Run the open helix aggregate, but leave the separators off.
  6. Move to LBSEQ = 1 and correct the orbit using setup 10, but change the slot range, and use the proper T39 file..
  7. Establish circulating beam with tunes at Qh = .588, Qv = .573 and the minimum tunes split < .003, and xx = xy = 4
  8. Turn on separators (should we do feeddown scans on both helices?)
  9. Make feeddown scans of S1, S2, S3 by filling in spread sheet. (This step should be done at LBSEQ 1)
  10. Leave tunes at Qh = .583, Qv = .576, minimum tunes split < .003, and xx = xy = 4 and then go back and inject with the octupoles on.  Use the LBSEQ = 0 slot to keep the tunes, coupling, chromaticities as stated.
  11. Turn separator power supplies off
  12. Go back to LBSEQ = 1, and make sure the orbit is perfect.

Accelerate and Squeeze

  1. Copy the DFGs up to 980 GeV
  2. At 600 GeV, do a -1mm bump at HF32, HF44, HB26, and HB38
  3. At 700 - 980 GeV, do a -2mm bump at HF32, HF44, HB26, and HB38
  4. Accelerate
  5. Smooth 200 - 980 TOP setup file 10.  150 GeV should not need smoothing.
  6. Make sure Flattop orbit is as we want it, and re-correct if necessary.
  7. Set the tunes to Qh = .583, Qv = .576, minimum tunes split < .003, and xx = xy = 12
  8. Goto Low Beta
  9. Correct the orbit to be as good as possible.
  10. Set the tunes to Qh = .583, Qv = .576, minimum tunes split < .003, and xx = xy = 12
  11. Collect lattice measurement data for Alex to analyze.

Next work on either 150 GeV helix or Central orbit acceleration ramp

150 GeV helix

  1. Make sure Feeddown scans done earlier have been incorporated to C49 before continuing with this task.
  2. Inject and turn separator power supplies on.
  3. Set tunes at Qh = .588, Qv = .573 and the minimum tunes split < .003, and xx = xy = 4 (Adjustments done in LBSEQ 0 slot)
  4. Without using event $D4 open and close helix by triggering events $C3 and $C0.
  5. Tune up the helix using the spreadsheet linked above.  There is a worksheet tab for "helix tune up".  Some numbers are filled in with the desired numbers.  Make sure the numbers in yellow are still correct as they were filled in during the shutdown.  The blank yellow boxes need to be filled in during the tune up, and the blue numbers should be the correct calculated numbers to insert into C49.  Once this is done, make sure the tunes and coupling really don't change when the helix is opened in both polarities.
  6. After finishing with the spreadsheet, return the tunes to .576 and .583.
  7. Keep track of any changes needed in the open helix ramp.
  8. Ignore the feeddown changes, but subtract any changes made from the energy slot, and add the changes to the LBSEQ 0 slot.
  9. Make sure that from injection, to open helix, to LBSEQ 1, the tune up looks good.

Acceleration on the Central Orbit

For this portion of startup, the Tevatron will be placed in a continually ramping mode.  For this, the TLG must be 220 seconds long with event $41 at the beginning.  We need a Tevatron injection module placed between 2.3 and 7 seconds after the $41.  Run the "Recovery" aggregate, and then turn the separator power supplies off.

  1. Make sure the orbits are good at all breakpoints.
  2. Set the tunes all the way up the ramp so that the vertical tune stays at .574 and the horizontal tune stays at .588.
  3. Use Eliana's program to decouple at each break point.  Make sure you plot the kicker and energy so you are sure the kicker is firing at the correct time/energy.
  4. Once decoupling is complete, reset the tunes at each energy to obtain constant tunes up the ramp at .574 and .588.  Make an E-log copy of the tune and coupling tables at this point.
  5. Raise Qv by .007 and lower Qh by .007 at each energy break point so that the tunes should be on top of each other.  Get an E-log copy of the tunes up the ramp.
  6. If things are good, lower Qv by .005 and raise Qh by .002 at each breakpoint.  The tunes should stay at .576 and .583 all the way up the ramp.  There will be some motion at the beginning of the ramp as the Octupoles turn off.

Tune up the flattop Helix

  1. Make sure the flattop centered orbits are just how you want them.  Use TOP setup _________
  2. Turn on the separator power supplies and fill in the flattop portion of the Helix Tune up spreadsheet.
  3. Once you are done with the spreadsheet, return the flattop tunes to .576 and .583.

Parse the Squeeze

Before finishing the Parse, make sure Alex is happy with the sequence 25 lattice.  Enter Parse and begin stepping through the squeeze.  At each step,

  1. Make sure the orbit is good with the separators off.  Use setup __________________
  2. Insure the min tune split is less than .003
  3. Set the tunes to .576 and .583
  4. Turn on the Proton helix.
  5. Adjust the Feeddowns so the min tune split is less than .003 and the tunes are .576 and .583.
  6. Turn the separators off and verify the Central orbit tunes and coupling are still correct.
  7. Go to next step of squeeze.
  8. Measure the chromaticity at every 4th step.

 Ramp on the Helix

  1. Use the tune tracker and page T127 or just the VSA?
  2. Ramp once on the central orbit and record the tunes up the ramp.
  3. Ramp on the Proton helix and record the tunes at each break point.
  4. If the tunes are different by more than .002 at any break point, try to correct them with the tune feeddowns.
  5. If the helix tunes cannot be corrected because of differential coupling, USE ELIANNA'S PROGRAM OR.....?

Miscellaneous tasks

Questions about startup