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).