Updated June 19, 2006

Periodically separator scans are preformed to verify proper separator angles at the IP’s in order to maximize luminosity at each IP.  The following is a process for conducting these scans.

Time to do scans:  Typically it takes about 2 hours to complete the scans at the end of a store.  You should not get large proton or pbar losses during the scan.

Separator Scan Procedure:

Use parameter page C16-BUMPS subpages:

          <2> for Hor and Ver B0 Position bumps.

          <1> for Hor and Ver D0 Position bumps.

         <3> for Hor and Ver B0 Angle bumps.

<4> for Hor and Ver D0 Angle bumps.

1.     Before starting the scans,  inform CDF and D0 that separator scan are going to be conducted and that they should leave their luminosity and proton and pbar halo loss signals up.  (C:B0ILUM, C:D0FLTL, C:LOSTP, C:LOSTPB, C:D0AHTL, C:D0PHTL)  These are necessary for these scans.

2.     Next all the collimators will need to be retracted from the beam if they are in.  They will need to be retracted ~ 4mm.  This can be done by issuing TEVCOL mode 5 for proton collimators and TEVCOL 11 for pbar collimators about 3 to 4 times from the sequencer.

3.     Start 2 plots be going to the utility window under FTP and RESTORE plot Collider “60 separator scan losses” and “26 separator scan”.  The X value for the plots should roughly have limits 80kV to 100kV.  Also go to C39 and put a plot of the tunes in the Tev eLog before starting.

4.  Disable orbit stabilization by setting T:ORBFB to 2.  (The orbit stabilization info can be found on T55-CALC VALUE sub-page 6.)

5.     The reference devices (f devices) on C16 <1>, <2> ,<3>,<4> will have to be disabled in order to knob the mults.  (Disable all parameters in mults on these pages).  You can use the ACL script "SEPS_REF_DISABLE" on page C9 - .STATES subpage 11 to disable all the separator references easily.

6.     Caution: The separators should not exceed 120 kV or 0 kV. Now go to the C16-BUMPS pages and knob each set of mults to produce a plot of luminosity vs. max separator voltage.  Fig 1. is an example plot.  Be sure change the X-axis device on the plot when switching to a new mult; use the device with the largest mult coefficient for the X-axis.  Choose sensible scale limits, too.  Repeat for the other separator bumps.  Note:  The tunes should not change while knobbing these mults and the scans should be independent of each other.

7.     Leave the mult at the maximum luminosity point and put a copy of the C16 parameter page and the FTP of the scan for each set of mults in the Tev eLog when they are complete.

8.     Once all the mults have been scanned, enable all the separator reference devices that were disabled to knob the separators on all the subpages.  Remember that they will not enable until they see a clock event, e.g., the $C6 unsqueeze.  You can use the ACL script "SEPS_REF_ENABLE" on page C9 - .STATES subpage 11 to enable all the separator references easily.  Finally, go to C39 and record a tune picture and place in the Tev eLog.

9.  Re-start orbit stabilization by setting T:ORBFB to 1.

Fig 1:  Examples of separator scan plots.  D0 vertical position and D0 vertical angle scans.

Putting Separator Scan Results into C49:

Once a separator scan is completed.  The resulting values for the separators will need to be put into C49.  The following commands will instruct how to put those values into C49 or you can use the new C49 separator value calculator.

1.     The scaling for converting separator values from KV to urads is:

(urad) = (the value of the separator(kv)/9.533)*# of sep modules

The number of separator modules can be found on C49 group separators under the change_calc menu item.