Notes from Main Injector/Recycler Group Meeting Monday, 23 September 2002 Bruce C. Brown Cons: Progress in Sequencer Aggregate Development It has been realized that substantial simplification in sequencer aggregate development is possible by combining pbar and proton aggregates. To distinguish the two, a new ACNET pseudo-device (virtual device) called V:RFMODE has been defined. The user sets this in response to a prompt (usually early in an aggregate) and it is used to control choices through the aggregate. V:RMODE has allowed values of 1 proton 2 pbar 3 none The newly completed aggregates have been tried on protons and are expected to be tried on pbars this evening. C. Bhat: Coalescing Pbars Pbar coalescing was broken late last week (Thursday, September 19). This was eventually traced to a failure of the MIRF Station 17 phase detector. It was oscillating on its own, resulting in improper paraphasing to achieve the voltages required for coalescing. After it was repaired, the coalescing tune-up was again possible. A plot of coalescing efficiency vs. transfer number was then shown for recent shots. Early transfer numbers (1, 2, 3.. in given shot) showed efficiencies in the high 80%'s range while later transfers (7, 8, 9) showed coalescing efficiencies nearer 70-75%. Each point was an average over the last 4 (quite good) shots. Average over the transfers and shots was about 78%. Shekhar suggested that plots vs longitudinal emittance from the Acc would be more revealing. Next, a plot of longitudinal emittances vs. transfer number was shown for Shot 1748, including MI at 8 GeV, MI at 150 GeV before coalescing and 150 GeV after coalescing. Variations were apparent for the uncoalesced beam but the emittance after coalescing was about constant at 3 eV-sec. This suggests that it is determined by the bucket area made available for the coalesced beam. Some discussion of bucket matching between MI and Acc ensued. Does the 47 kV Acc extraction RF (53 MHz) create a bucket which matches the bucket provided by 300 kV of 53 MHz in the MI? Observations in MI suggest that is is more suitable than naive calculations rumored to have been done by others have suggested. [Acc longitudinal emittance is obtained from a bunch length measurement in the transfer line plus Acc lattice parameters. It seems to adequately match the MI measurements.] The plot of the longitudinal emittance vs transfer number averaged over Shots 1727 - 1748 showed more variability than the plot for recent transfers. In particular, the first few transfers shows some shots where >90% efficiency was reported. Chandra observed that perhaps despite the good results from the recent shots, there is still room for improvement in this area. Shekhar has observed that the bunch length in the transfer line from the accumulator for the most recent shots is larger than it was for a while. Discussion: The MI longitudinal emittance measurement reports results for average length of each bunch or from the raw bunch length data from the SBD with RF parameters to convert to eV-sec. Pbar and MI agree on formulas at this time but no one believes that the TeV group reports things on the same basis. Alberto is on committee to resolve this but progress is slow. The transverse emittance is somewhat different on recent shots but not significantly. PBar reports 10 pi-mm-mr whereas MI at 8 GeV may sometimes be smaller. Sometimes the PBar and MI 150 GeV are in closer numerical agreement. Shekhar: Revised plans for Reviews in October The DOE review planned for the last week of October has been extended from 2.5 days to 3.5 days. It is expected that the additional time will be in 'breakout sessions' rather than presentations to the entire review group. The schedule now called for this review to be on Oct 28-31. The Directors review to prepare for this is now scheduled for Oct 17-18 but that may also be changed. Check your calendars for any impact of this schedule change and be alert for possible additional schedule issues. Shekhar: Recent Operations and Plans The week just ended achieved 4.7 pb-1 of integrated luminosity despite some problems which increased the time for shot setup. The announced goal for this era is 5 pb-1. It has been observed that the proton intensity in the TeV is limited by instabilities and impact on the pbars to about 250E9/bunch. We have been doing this with 10 Booster turns and 7 bunches. Can we achieve this with 5 rather than 7 proton bunches and more Booster turns? The longitudinal emittance would surely be reduced. The transverse emittance would probably be larger from the Booster but only a little bit. That might not be significant since the transverse emittance after TeV capture shows a much larger dilution than that. It was agreed that only a little study time was needed to tune up in this mode and see if it was as expected. Perhaps that could be tried just after the meeting???