Minutes of the 27 Sep 2002 Tev Dept Meeting 1. Dept news: - Dean Still will be next Tevatron coordinator starting Oct.1. He askes for summaries of proposed studies before Fridays - Thank you, XiaoLong Zhang, for job well done as Tev coordinator Aug.1-Sep.30! 2. CYTan visited BNL to see how RHIC tune tracker status and found that though it works but never was used yet for tune stabilization. His major concern is that it might not work at Tev because of the dampers. McGinnis disagrees with that and mentioned another possibility to attract CERN to test their LHC system at the Tev (Schmickler). 3. M.Church presented "Letter of Recognition" to Dave McGinnis for leadership and personal contribution in fixing the Tev injection errors which allowed recent progress in the luminosity. Congratulations, Dave! 4. XL luminosity report: last week we had record integrated luminosity (4.8 pb-1), this week we broke luminosity record with 30.15 in #1787 plus record pbars at low-beta 614e9 in the same store. In general,there were 5 stores since last Fri, two L-records, two N_pbar records, large proton bunch length compared to 1 week ago (2.2 ns at LB vs 2.0 ns). Avg L-lifetime is about 10 hrs early in stores that comes from N_p (50 hrs), N_pbars (40 hrs) and emittance (20 hrs, mostly pbar blow-up). 5. Jim S described two shifts dedicated to transverse (H only) bunch-by-bunch dampers: BTF remeasured and confirmed effective damping of beatron lines after (at most) about 1 ms (50 turns). The gain was reduced by 10dB to lower emittance growth. The damper affects instability at 980 and suppresses it at 150 with negative or small chromaticity. Jim was not sure in lifetime improvement due to damper, requested more time to finish H-damper studies and tune-up Vertical damper (all parts are here). 6. Vladimir (participated in the studies for few hrs) sees the damper results in somewhat more optimistic light as he thinks the damper is ready to be used at 150 GeV to lower both chromaticities down to about 2 units (from current 8) and, thus, reduce pbar losses at 150 (damper to be turned OFF before ramp and usual C_v,h restored). There was no significant emittance growth at 150 Gev with the damper ON, lifetime improved with lowering C_v,h from 2 hrs on open helix to 12(?) hrs. The only risk may come from possible bad effects while injecting pbars. It was decided to try having the damper ON at 150 GeV with reduced C_v,h (over next stores). Also, he reported a) decoherence time (decay of Schottky power) measured at injection is about 200 ms (10000 turns), and b) instability growth time is 50 ms (2500 turns) (when the damper was turned OFF and C_v,h=+1.5). 7. Peter Ivanov described head-tail studies with octupoles: he sees the reason of the instability in significant incoherent tune spread due to space-charge (-0.0012 at inj) which does not cover coherent lines.So, octupoles are supposed to introduce needed tunespread with positive sign of the nonlinearity dQ/dA^2>0. Currents in the TOZF and TOZD octupole curcuits must be positive. During (reduced) study time it was found that high intensity (>200e9/bunch) coalesced bunches are stable and even can be injected at low or negative chromaticities if TOZF is between 5 to 6.7A. The reason of the upper limit is not clear yet. Jerry thinks that more studies are needed before we can try to operate octupoles in real stores again (prevuious attempt took place in April). 8. Valery was able to improve Tev and A1 line BPM accuracy by using high beam current, focus of his attention is now on MI where he thinks the reason of the emittance mismatch is. Significant orbit distortions in MI sextupoles led to variation of the MI lattice from the design, e.g. significant coupling in MI was found and studiers were unable to fix that. He still observes larger emittance dilution after reverse injection from Tev to Mi thru A1 line (1.3 in V emittance and 1.8 in H emittance) and tuning current in Q902 (A1 quad) did not affect that much - contrary to model predictions. So, the search of dispersion mismatch in A1/MI is started. 9. Jerry briefly commented situation with tune/coupling drift compensation: the compensation works well, the system is in operation since after the studies, adjustments found during the studies allowed to stabilize the tunes at 150 to the level of 0.001 over 2-3 hours, coupling does not drift and stays at 0.003. Looks like tunes on ramp are more stable now, too, after some b2 reconsideration. 10. Vladimir delivered conclusions of Tanaji on larger hor helix separation at low-beta: 8% increase (and - after 4 hours - decrease) between B0 and D0 did not result in any significant changes of the luminosity lifetime in store #1775, so it is not recommended to have it permanently. 11. Alvin used 1 hr EoS studies to recalibrate abort gap counters by turning TEL OFF in store #1787. The calibration constant (count rate in B0MSC3 vs real number of particles lost per sec) is about the same as in his previous experiment few week ago and close to calibration made when one of RF station tripped and a godd chunck of protons fell off RF buckets and was "eaten" by TEL. As the result, his model ditribution of losses is: early in store: vacuum loss=0.6, lumi-loss=0.4, Dc beam =0, tranverse loss(dynamics)=1.7e7/sec (out of 6400e9 total); at the end of the store: vacuum=0.5, lumi=0.2, DC beam=1, transverse=small. Alvin also looked into the SBD/FBI signals and proposed changes which made the signals better (reflections moved off small satellites) 12. Paul Lebrun has presented preliminary results of the 150 GeV antiproton lifetime analysis: it depends on bunch number in train (grows by almost factor of 2 from bunch 1 to 12), lifetime is not constant in time (decay is not exponential), there is no statistically proven anticorrelation with pbar emittance (contrary to results of our previous studies). He mentioned that some instrumentation flaws are needed to be fixed for better analysis (FW emittance correction for pbars and FBIANG/WG recalibration). Also, more stores need to be considered. Results of the analysis are of great importance for estimating future improvement due to opening C0 aperture.