Some notes regarding electron conditions:

Last night I attempted to recover both the V15M and CD40 electron conditions. I spent about three hours between the two lattices, and I was unable to reduce the beam size below ~22 microns in either set. These conditions have been saved in EMBXRAY in both routes. The hysteresis loop has been defined such that you loop the machine, then load EMBINJ, then go to EMBXRAY. Dave can propagate the EMXBRAY conditions to ELLET so Walter's tune tracking will work.

It has been well-documented this run that electron conditions are very unstable compared to positrons (Mike Billing has also noted this in single-bunch conditions; train conditions are even worse). I have witnessed when locking the tune trackers the beam is extremely responsive, requiring a very low drive amplitude (and often still overdriving the beam). When the tune trackers are released, often the vertical mode will remain self-excited until the feedback is enabled, which then damps the beam immediately. The feedback can then be released, and the beam will remain damped. I have checked various settings, working points, chromaticities, etc., to no avail. (note: if you want to measure chromaticity tomorrow, use the VMS version of ximes and use the analog tune trackers, rather than the Linux chrom_meas). 

The orbitry has been annoying at best and painful at worst on C-line. The orbit will likely not come back after a loop, which means that when you start up on Sunday (recall: C-line setup shift is now occurring from 12-2pm, before the ODR shift), you will need to run an orbit correction. I will include the requisite incantations below. It should only require a minor flattening, with convergence in 1-2 iterations. Note that the lever arm on C-line is longer than on D-line, which means it is more sensitive to precise orbitry. I would advise against using vbumps to center the beam on the detector, though if necessary, VBUMP 10 has a stronger impact than VBUMP 5 (though the use of either will potentially result in clipping). 

Other known issues: 
-sk_q48w is still an unknown-- avoid using it if you decide to try to run LET corrections.
-QUAD 37E (#62) has a bad bit transition from 8191-8192CU. This causes a 2-3kHz tuneshift. This has been noted in the CESR Ops log. I would advise vetoing this quad if running phase corrections.
-Known bad BPMs for orbitry: 18, 48, 65, 80
-Known bad BPMs for phase/coupling: same as above, plus 35.

I will be in tomorrow around noon to help Nate with prepping C-line for ODR. The xBSM settings should be fine for what you want to do after that. Recall that D-line is not available for end users tomorrow-- it is set up for bunch slicing measurements, and cannot be transitioned back to "normal" operation.

Let me know if anything needs further clarification. I will be available by phone (likely home phone, the 607 number on the control room contact list) if all hell breaks loose. 


Best of luck,
Jim



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! C-line orbit recovery - CESRv incantations
! for after a loop, assuming you've taken an 
! orbit already and read it in:
read ref o:805323
set ref_orbit_x(13:99)=0
set ref_orbit_y(13:99)=0
veto orbit 18 48 65 80
set orbit_x_wgt(0:12)=1.e8
set orbit_y_wgt(0:12)=1.e8
use horiz 0:15
use vert 0:15
show top
! at this point, you can run and load corrections. 
! This has been tested and shown to recover 
! the same emittance as before the loop. You 
! may have to iterate the correction twice to 
! get full convergence. 
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