Minutes of the Feb 25, 2005 Tevatron Dept Meeting

1. Dept news: Ezio Todesco - a visitor from CERN - returning back to CERN
next Thursday, we thank him for his participation in studies of Schottky
signals (with Paul and Tanaji).

2. Ron on operations: 8 stores, Lumi btw 59 to new recod high 107e30
(#4002);  longitudinal instabilities in few stores beam spilled in
abort gaps, but no quenches on abort even with AGIGI2=45e9; one store lost
due to abort kicker prefire; A49H seprator polarity switch had problems
--> taken OFF; moving pbar SL mirror in and flying FWs sucessfully tried
in stores.

3. Jerry analyzed 33 stores since Jan 6, 2005 and reported that with
current abort limits on the loss rates we'd falsly lose 22 stores if the
BLMs were enabled; while only 3 quenches would be avoided - that poses an
issue of how to set the BLM limits if we want to enable BLMs for
the machine protection.

4. Jim Steimel decribed longitudinal instability accidents in 3 stores
2/18-2/20: he and Tan performed beam transfer function measurements and
found the BTF of the longitudinal damper be the same as 3 years ago;
instabilities start as mode 0 (all bunches shifted in phase together) and
later develop into mode 1 or 3; the damper does not damp mode 0 (but an
older Fixed Target mode 0 damper is available and can be tested); during
the testing, they found that touching various cables can generate
intermittent noise and advised a) to disconnect LPM001 which uses nearby
sockets from the same detector; b) check Robinson stability condition (RF
cavity resonant frequency); c) reduce the gain of the long damper toward
the end of stores (that's what Ron is doing all the time now).

5. Alvin added that during 2/20 accident, the proton bunch shape
distortion was quite weird (2-3 sub-bunches) but the same for all bunches.

6. Yuri showed a simple derivation of the Robinson stabilty criteria and
presented a study plan to find whether Tev cavities are properly tuned (by
changing their resonant frequencies by +-(few 100's) of Hz using water
heaters). He also noted that asymmetry of the p-Schottky spectrum in
collisions (see last week notes) can be due to bunch-by-bunch tune
distribution.

7. Jean-Paul Carneiro compared beam RF phase shift on the ramp measured by
LPM001 with calculated one and found that LPM should be scaled by factor
0.55-0.65. Many other features on the ramp and during cogging still wait
for explantion (e.g. a glitch at 300 GeV).

8. Stephen P and Bob Flora tried to solve a puzzle of why SBD proton
intensity grows on ramp and adjusted a digital FIR filter compensation
dispersion in the signal cable --> they were able to make the bunch shape
"right" with 20% filter correction but not the intensity (the 20%
correction is taken out).

9. Andreas (and Ralph P and Paul) did introduce an autoscaling feature
into the 1.7 Schottky VSA and that (together with recent replacement of
multiplexor boxes) allowed them to increase S/N ratio; now they can see a
single pbar bunch (15e9 17 pi) tunes with accuracy +-0.0005. Also, a
simple theory of the detector (doc-1576) shows that reported V and H tunes
can cross - as if the detector reports "tune settings" - the phenomenon we
observed many times in Tevatron; measured Pbar Tunes for all 36 bunches
are about what they should be; pbar dP/P from 1.7 Ghz agree perfectly with
SBDAMS; even transverse emittances from Schottky resemble the pattern
measured by FWs.

10. Nathan Eddy analyzed proton emittances in the stores after FY'04
shutdown: expectations were that (for bunch P2) the emittance growth at
150 GeV caused by FWs should reduce by 0.5 pi (as two thin 7 um wires were
installed at E11 and only one 33um wire left at E17) - and that's exactly
what he observed (1.1+-0.3 pi -- >0.6+-0.3 pi). There are still some
discrepancies left (e.g. D_x at E11 measured by FWs is 1.7 m while in the
standard Tev lattice D_x= 2.9 m).

11. Vaia summarized recent meeting with CDF and D0 luminosity monitoring
groups: D0 found that with proper deadtime correction their L will go
up 10% or so; D0 beta^*_x/y is about 33/37cm; CDF just started to report
beta^*_x,y off line and their values are 15-20% smaller.

Minutes recorded by V. Shiltsev; edited by R. Moore