Minutes of the 27 May 2011 Tevatron Dept Meeting

https://indico.fnal.gov/conferenceDisplay.py?confId=4483

* Summary of Weekly Operations (Bruce Hanna) - Over the past 2 weeks, there
have been ~123 pb^-1 delivered to the experiments. There have been 19 HEP
stores with initial lumnosities between 114 and 405 ub^-1/s. Only store 8741
was lost prematurely when the D2 cryo wet engine failed.  A series of computer
network "storms" were found to be caused by a transient recorder in the D0
service building. A leak of SF6 in the E48 kicker supply was found and fixed.
Numerous TEL-1 trips fixed by cleaning air filters for a power supply. The A1
house 2-phase He pressure was raised to 9.0 psia to help stabilize cryo.  An
EchoTek card for the C4 BPMs was replaced to fix hang-ups of the VME crate.
A number of roughing and turbo pumps were replaced in the tunnel. Insulating
vacuum in the upstream half of B4 is slowly degrading.  The Tevatron injection
energy was lowered a wee bit to better match Main Injector and reduce
synchotron oscillations at injection.  A series of crystal collimator and 
hollow electron beam studies have been performed over the past 2 weeks.

* Summary of Crystal Collimator Studies (Dean Still) - The T-980 team conducted
~24 hours of end-of-store studies over the past 2 weeks to characterize 3
crystals and commission a pixel detector to directly image channeled beam.  The
pixel was successfully used to observe channeled beam separated from the halo
of the core beam.  The performance of an  O-shaped crystal and an 8-strip 
crystal were characterized.  Channeling from a 16-strip crystal was not
successful - when rotating the crystal, it seems the leading edge would dip
into the core beam.  Simultaneous 2-plane (horizointal and vertical) channeling
was inconclusive and needs additional development time.  Lots of valuable data
were collected and they will be busy analyzing it for some time.

* Summary of Hollow e-Beam Studies (Giulio Stancari) - Hollow e-beam 
collimation studies were conducted in 3 end-of-store studies and 1 pbar-only
store (17 hrs total).  They were able to measure beam diffusion rates vs
electron current and hole radius both with and without colliding beams. In 
general, the beam diffusion is much faster with the electron beam above a 
minimum electron current. They observed that the e-beam can reduce the 
amplitude of loss spikes that can be caused by low frequency beam motion 
(toward/away from collimator).  They also investigated the effect of pulsing 
the electron beam at different frequencies. Additional studies are waiting to 
be performed. CERN is now very interested in obtaining an electron lens for 
additional studies done in the SPS or LHC.

* Plan for Next Week (All)

   - Deliver luminosity.
   - Enjoy the Memorial Day holiday.
   - Lumi leveling via Bunch Length (Ron, mid-store)
   - Collimator extinction (Dean et al., short proton-only @ 150 GeV)