Minutes of the 25 Oct 02 Tevatron Dept Meeting

1) News by Vladimir.  Ray Stefanski will lead an effort to survey and
align the Tevatron components.  He will act as an interface between Tevatron
Dept, Deputy Division Head, and Survey Personnel.

   The RF&I Dept is being split into two separate departments.  Ralph
Pasquinelli will lead the RF part, and Bob Webber will head the I part.

   Members of the Director's Review committee were pleased with the progress
of accelerator complex performance since January and with our planning for
FY03.  They believe we can readily achieve our goal of 200 pb^-1 delivered
luminosity for FY03.   The DOE Review comes to town next week 28-31 Oct.

2) Dean reviewed our less than stellar week delivering luminosity.  We had
one good store (~35 e30 peak lumi), a shutdown and its associated problems
coming back up, one poor store (~15 e30 peak lumi), and a couple of lost
stores caused by quenches at A11 early in the squeeze.  The differential
coupling was improved, and the vertical at flattop was raised; this work
helped reduce losses at A11.  It was also noticed that the pbar cogging
at flattop causes a few spikes of beam loss at A11, but this was *not* the
reason for the quenches.

3) Bruce reported on a second meeting with Argonne vacuum experts and some
studies which were performed.  The Argonne people recommended doubling the
number of ion pumps in the Tev, and to use differential diode ion pumps to
improve pumping of noble gases.  The Argonne group is willing to continue
to give advice, but they will not make any specific designs of vacuum systems.

   Bruce conducted an experiment in which he turned off all of the cold 
section ion pumps during an HEP store.  There was no effect on luminosity,
losses, or emittance growth rates.  It was noted that the cold vacuum at D1
and D2 is relatively bad.  Bruce will study the warm sections next.

   Bruce also outlined shutdown work which should help vacuum in the Tev.

* new H degassed beam pipe and bakeout associated with
   - C0 lambertson replacement (MI dipoles retrofitted with heaters)
   - B48 abort kickers
   - new Schottky installation @ E17

* new 200 L/s ion pumps @ F0 lambertsons (currently 30 L/s) to better match
  the conductance of the beam pipe (~200 L/s)

  Vladimir and Bruce discussed recently observed behavior in cold ion guages.
First, there is a strange 30 min oscillation in the reported pressure
(amplitude is ~50% of the average reading of 1-3 10^-11 torr).  
Second, the pressure readings differ by ~factor 2 between 150 GeV and 980 GeV.
The effect is likely caused by magnetic field differences between the two 
energies, and not caused by synchrotron radiation.


4) Jim Steimel summarized progress on Technical Division help in looking for
sources of RF noise which might cause DC beam generation at 980 GeV.  One
person is studying mechanical issues, the other electronic.  Current focus
is determining if an observed mode at 37 Hz (happens to be the synchrotron
oscillation frequency at 980 GeV) arises in the RF drive or the cavity itself.


5) Ron reported on status of studying/installing a small (~0.5m) collimator
at A 48 that, according to simulation, could reduce losses of protons at B0
by roughly an order of magnitude.  There are two problems: 1) there isn't
enough space to install such a device (only few inches at most), 2) simulation
of secondary particles coming from such a collimator is halted due to a software
bug.  Qualitatively, background from that collimator would negatively affect
operation of the CDF Roman Pots.  A quantitative analysis awaits the simulation.
CDF (at least the pot proponents) would likely not want to sacrifice the 
diffractive physics for that new collimator.  CDF will proceed adding
steel shielding around the low beta quads in the collision hall during
the next long shutdown.

   The halo task force has asked the experiments to describe how the beam halo
background impacts detector operation and physics analyses.  We expect feedback
in 2-3 weeks.  We will use that information to evaluate the need for future
improvements in beam halo reduction.


6) Jim summarized recent transverse damper operation.  The vertical damper
has been commissioned.  The horizontal damper had a problem with its
autozero circuit which required a local reset.  Both dampers are being 
used for HEP shots at 150 GeV only.  Beam lifetimes do benefit while
damper is on, but when the dampers are turned prior to ramping, there is
a rapid beam loss roughly equal to the loss seen prior to damper usage.
using the dampers on the ramp is complicated by the lack of a phase-lock
loop, but we will likely try it anyway to see the effect.


7) Ron presented continuing work on longitudinal proton oscillations at
injection.  Based on a suggestion from Vladimir, Ron showed the how
the sigma (from a Gaussian fit of the Mountain Range waveform data) of the 
bunch length varies versus turn number in the Tev.  Although oscillations 
aren't obvious from the fitted mean position, the sigmas clearly show
an oscillation which gets damped.  The beam isn't terribly Gaussian at
injection, but the sigma varies by a few hundred nanoseconds because of the
"nipple" which oscillates back and forth in the profile.

   Ron also showed data which resolves a bunch length disrecpancy between
the Main Injector and the Tevatron.  The MI typically reports coalesced proton
bunch length RMS between 2.8 and 3.0 ns using the MI SBD.  The Tev SBD usually
reports sigmas between 3.7 and 4.5 ns.  Using raw data from the MI SBD
at extraction and the Tev mountain range at injection, a comparison was
made between an RMS calculation and sigma from a Gaussian fit.  The RMS
calculation for the MI and Tev raw data agreed; the Gaussian sigma calculations
also agreed.  So, there is no longitudinal bunch length blow-up between
MI and Tev; the measured lengths agree when you compare the results
from the same algorithms.  The RMS and Gaussian sigma don't agree well because
the bunches are not Gaussian (after coalescing at 150 Gev).  The relevant
parties will meet and discuss modifying SBD algorithms; making both
RMS and Gaussian calculations sounds like a good option.


8) Xiaolong described a recent attempt to try to see pbar tunes with the
Schottky detector during an HEP store.  They tried tickling the pbar bunches
to look for a tune line on the pbar Schottky signal.  No line popped up, all
you could see ws the response from the protons.  The Schottky will be tuned
up to look for pbars, and they'll try again.


9) Paul Lebrun showed the result of an analysis of pbar bunch lifetime at 150
GeV.  Vladimir had noticed fitting the pbar intensity to e^(-sqrt(t/tau))
actually fit the data well for one store.  Paul tried this for all 36 pbar
bunches over several stores.  Amazingly, that function describes the pbar
lifetime pretty consistently.  There is no correlation between the 
"sqrt lifetime" and bunch length.  We'll work on understanding the physics
behind such lifetime behavior.  


10) Peter Ivanov described recent progress in making a head-tail monitor using
the stripline pickup.  They injected a single coalesced proton bunches at
different chromaticities; Peter showed great pictures of the growth
of the instability as chromaticity was lowered.  He also demonstrated how
the chromaticity can be measured using this data.  Perhaps we can use this
method to make online measurements of chromaticity with coalesced beam!
Peter also estimated the Tev transverse impedance based on the head/tail
instability growth rate.  He measurement of 3.2 Mohm/m is close to the 
expected 2.0 Mohm/m, although a difference in the expected/observed bunch
length was not taken into account.  It is clear that this configuration
can detect oscillations of ~1 mm amplitude...it is not clear if it can
see much smaller oscillations ~50 um which could be generated by gently
tickling the beam while try to measure tunes.