Minutes of the 11 Oct 02 Tevatron Dept Meeting

1) Mike Martens reported on a meeting held to discuss implementing A0
lattice changes.  The "ideal" solution would be to make A0 look like E0; the tune
is calulated to change by 0.002 from the current situation.  However, that
modification would require moving cryo bypasses, which is difficult, and
would not be ready for a January 2003 shutdown.  Another option involves
moving dipoles without modifying the bypasses.  Investigation of the lattice
changes for that option is underway.

2) Vladimir summarized John Johnstone's new proposal for replacing the C0
lambertsons.  This solution uses existing superconducting magnets, not MI
dipoles.  The half-dipole at C12 would be replaced with a full dipole; two
full dipoles and two half-dipoles would go into B48; sync lite would move
to B48 as well.  Additional spool pieces would be needed to generate the
remaining needed bend field.  Issues to be studied: compensation of
sextupole fields (Alvin says the half-dipoles have more significant sextupole
components), using a full dipole instead of two half-dipoles at B48, effect
different beam positions on sync lite operation.

3) Dean provided a summary on a very good week for the Tevatron.  We broke
the peak luminosity record on two consecutive stores; new best is 36.1 e30
(store #1836).  We also surpassed a milestone by delivering > 5 pb^-1 for
the week.  (Actual number is about 6.7 pb^-1, previous best = 4.9 pb^-1)
Store 1836 also a record number of pbars to low beta = 855 e9.
Store 1839 suffered from lower luminosity and higher losses because one
pbar transfer ended up one bucket off; Vladimir removed the offending pbars
with the TEL.  Overall pbar efficiency to collisions has been good (>~ 60%),
and the proton bunch length is smaller too (2.2 -> 2.0 ns).
Luminosity lifetime has decreased to 6-8 hours during the first
two hours of the store; the emittances are growing more rapidly recently.

4) Vladimir observed that the pbar bunches within each train grow
more rapidly than the leading and trailing bunch of each train as seen by
flying wires and sync light.  This effect is caused by the differing
beam-beam tune shift with the trains.  We should try to adjust the tunes
for bunches within the train either by moving the tune and/or feeddown
circuits or by using the TEL for its designed purpose!

   Vladimir also provided some predictions of initial and integrated
luminosity versus store length based on recent pbar source and tevatron
performance.  The model suggest that keeping stores longer (19-21 hours
versus the current typical 14-16 hours) would increase initial luminosity by
allowing larger stacks as well as integrated luminosity by keeping stores
longer when lifetime is best.

4) Vladimir and Alvin made presentations about pbar FBI discrepancies.
During store #1828, Vladimir varied the number of buckets used in the pbar
wide-gate FBI measurement and determined each bucket added ~25 e9 to the
reported intensity.  As Alvin pointed, this offset is not applicable to
the narrow-gate FBI (WG and NG offsets are different).  It is
clear that we need a better understanding of the background subtraction
in the pbar FBI.  That device should also be calibrated to the T:IBEAM DCCT.

5) Ron showed the first phase oscillation data obtained with Dave McGinnis'
scope-based TBT system.  One of the proton injections from store #1836
showed a 6 degree amplitude oscillation (corresponds to ~0.5 ns) and looked like
an energy-mismatch.  The 4 pbar transfers with phase data showed
oscillations with ~15 degree amplitudes (0.85 ns).

   Ron also analyzed phase oscillations for protons using the raw mountain
range scope data.  The proton bunch wave forms were fit to a gaussian, and
the mean position was plotted over many thousands of turns.  Jitter in the 479
card output (~1 ns) used in the scope trigger washes out oscillations of that
order. However, the mountain range data seemed consistent with the TBT measurement
of <= 1 ns amplitude oscillations.  The mountain range data for P1 and P36
also were consistent, therefore, we probably do not have
long-emittance blowup due to beam loading.

6) Tan reported on effect of using the horizontal damper during shots.  We
have been using the dampers on alternating shots for the past week.  The damper
does not make an obvious improvement in lifetimes on the helix, but it also does
not harm performance.  The damper will be left on for all shots now unless
an obvious problem results.  We anxiously await progress with the vertical
damper commissioning (waiting for beam time).

7) Peter Ivanov showed plots on head/tail instability monitoring he and Vic
are developing.  They did 3 injections of coalesced protons with high/low
horizontal/vertical chromaticities.  They recorded an instability using
the vertical stripline (and TBT) when both chromaticities were ~+2.
The beam aborted before 200 turns < 3 synchrotron oscillations; that
instability seems too fast, would expect it around 20-50 oscillations
instead. They will repeat measurements and record the sum and difference stripline
outputs, not just the raw signals.

8) Vladimir presented one slide from Paul LeBrun: (real/calc Lumi) is
closer to 1 after recent ANG recalibration.

9) Tanaji presented initial results from a study of ramp efficiency.  A
proton-only store with various bunches (uncoalesced, coalesced over various
intensities, # bunches coalesced, etc.) was prepared and ramped.  For the
coalesced bunches, the reported bunch length in the tev at injection was ~1
ns bigger than had been reported in the Main Injector; that is not yet
understood. Ramp efficiency was most strongly (anti-)correlated with bunch length (the
smaller the length, the better the efficiency up the ramp) with N_protons
and with vertical emittance. It's still unclear what is the major factor
(more studies needed).