Minutes of the April 22, 2005 Tevatron Dept Meeting

1. Dept news: a) Dean, Valery, Mike Martens, Pierre Bauer and Georgiu
Velev received FNAL EPRA awards for their work on Tevatron -
congratulations!; b) Jerry and Dean were at CERN for a week of Apr 11 to
participate in LHC machine protection review; the issues are serious, a
collimator group bigger than Tev Dept is working on them, LHC orbit is
going to be globally corrected at 25Hz rate to keep losses under control.

2. Jerry on operations: 4 stores since last Fri, L btw 70 and 110 e30,
octupole circuits O1 and O2 were introduced in operations and pbar and
p-losses at 150 were record low in 3 stores after that. Occasional E4 pbar
losses at injection still not understood. D0 losses at seq24 need to be
addressed, too.

3. Ron on variation of helix size store-to-store (>25 stores since March
1, 2005): for the same luminosity and same effective emittances, lifetime
is +5-10% better if helix size is 110% of nominal, and -(5-10)% worse if
90%.

4. Vladimir analyzed store 3869 when a separator error led to 2.6 sigma
displacement at IPs and 0.3 mm helix reduction at the first parasitics:
seems that head-on beam-beam effects dominated proton lifetime reduction
(makes sense as pbar emittance is smaller than proton) and long-range
effects dominate pbar lifetime deterioration (head-on effects are weak
because proton emittance is larger).

5. Vahid observed that chromaticity at 150 GeV is about 1 unit lower for
high intensity coalesced bunch than for low-intensity one; standard RF Q'
technique requires +40 Hz of RF freq change that results in -+3 mm orbit
distortions which shift chriomaticity by +-(1-2) units due to presence of
octupoles.

6. Yuri added that measured cubic chromaticity is large so hor
chromaticity should by +1.4 units higher for coalesced bunch (due to
larger dp/p). That contradicts Vahid's observations (item 5).

7. Vladimir summarized EoS 4105 study when chromaticity was dropped from
8-10 units to 0-2 units: a fast (<1 s) instability occured, pbars
were more excited (we quenched on pbar losses), there was significant
difference of bunch-by-bunch amplitudes (i.e. it's a multibunch effect);
no head-tail instability observed (per Vahid). All that makes the instability
with pbars very different from slower instability with protons only (in
36x0).

8. Study list includes: a) seq23-25 work to reduce D0 losses; b)
tune tracker (to finish commissioning); c) inj dampers (need >1 shift);
d) tune and Q' drift at inj; e) calibrate E0 ladder at 150; f) Ac
chromaticity at inj; ... and 5 more


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