Minutes of the Aug 26, 2011 Tevatron Dept Meeting

https://indico.fnal.gov/conferenceDisplay.py?confId=4790

* Weekly Operations Summary (CY Tan) - Another rough week for the Tevatron and
the rest of the accelerator complex - only 23.3 pb^-1 delivered to CDF and D0.
There were 9 HEP stores with initial luminosities between 107 and 308 ub^-1/s.
Electron cooling for pbars in Recycler was unavailable most of the stores.
Store 9005 was lost due to a thunderstorm-induced power glitch and quench.
Store 9014 ended in a quench soon after it started when a vacuum leak developed
on a warm beam tube bellows at A17; investigation & recovery took ~24 hours.
The voltage on the B48 separator positive plate was found to be wandering 
ocassionally from its nominal 68 kV down close to zero causing jumps in 
luminosity; the power supply controller electronics were replaced. The SF
sextupole power supply tripped off during a study store.  All of these 
problems all impacted/delayed dedicated beam-beam studies.  

* Summary of Beam-Beam Studies (Frank Schmidt) - Frank summarized the
attempted studies so far with preliminary results. Collisions with partially-
separated beams showed neither high beam losses nor large emittance growth
predicted by model.  Without electron cooling, looking for coherent beam
oscillations with high intensity, low emittance pbars was not performed.  With
3x3 colliding beam store, it was possible to set chromaticity to any value
without instability; a 3x0 proton-only store went unstable very quickly with
chromaticity just above 0.  Progress was made using the AC dipole with
colliding beams (in a weak-strong scenario) to try to measure the lattice and
observe beam-beam driven resonances; we're trying to get turn-by-turn BPM
measurements for pbars working before Frank departs.  In another 3x3 store, 
the beta function where collisions occur was changed by cogging the pbars
(moving them longitudinally relative to proton with RF by up to 10 m); beam
lifetime quickly deteriorated, will be compared to expectations.  Overall, it
was a useful study period, despite the difficulties with downtime.

* Discussion of Next Week's Plan

   - Return to normal operation and luminosity delivery (if the machines
cooperate!)
   - Crystal collimator (T-980, 3 hrs end-of-store)
   - Luminosity leveling (Ron, start of store)