1 PEP Status M. Sullivan MAC Review Nov , 2007 M. Sullivan for the PEP-II Team Machine Advisory Committee Review November 15-17, 2007 Run 6 Summary and Run 7 Startup Plans

2 PEP Status M. Sullivan MAC Review Nov , 2007 Outline Run 6 summary –Brief history –Magnet protection failure –HER instability aborts –MDs –Records Run 7 startup –Initial startup plan –Plan for the first 2-3 months –MDs –3S? Summary

3 PEP Status M. Sullivan MAC Review Nov , 2007 B-Factory Overall Best Parameters ParameterPEP-II (LER/HER) Circumference (m)2200 Beam energy (GeV)3.1/9.0 Number of bunches1732 Beam currents (mA) (e + /e - )2900/1900 Horizontal emittance (nm)30/50  y * (mm)9-11 Bunch length (mm)10-11  y (+/-) 0.065/0.045 IP beam sizes (microns) (x/y)120/4 Luminosity (x /cm 2 /s)1.2

4 PEP Status M. Sullivan MAC Review Nov , 2007 Improvements and Upgrades for Run 6 Two new HER RF stations in and working. We now have filled out the RF systems for both rings. Eleven klystrons (10 SLAC type) for the HER and 4 klystrons (2 SLAC type – one SLAC tube added this downtime) for the LER. LER BPM button removal in IR2 and BPM replacement in 5 of 6 arcs New skew quad fix for IR2 LER x-y coupling found and implemented. Specific luminosity is higher. More luminosity gain is expected in the future. Fast dither IP feedback in and working on a routine basis Vertical vibration in IR support tube damped with BaBar’s help Schwarz, Rivetta, Van Winkle Wittmer, Yan Fisher

5 PEP Status M. Sullivan MAC Review Nov , 2007 Run 6 Difficulties Our startup last January was slower than we had hoped –Reconfiguring the RF systems to include the new stations took longer than planned –Soon after startup we discovered that we had to remove a vacuum valve from a place where the previous valve had heated up. We had installed a new valve together with a HOM absorber. We hoped we had mitigated the HOM power in this location where the level is high. Apparently not enough. –We also developed a vacuum leak in a transition piece in Region 6 that had to be replaced

6 PEP Status M. Sullivan MAC Review Nov , 2007 More Run 6 History In early April we discovered a vacuum leak in close to the detector on one of the new vacuum chambers we had installed We also discovered the support tube inside the detector was vibrating vertically at about 9 Hz. While devising a mechanical fix we used the fast lumi feedback to cancel the motion. By the middle of April we realized we would have to take out the new chamber and put the old one back in and we set that up for the first week in May On May 1 st we turned off and started work on replacing the leaking chamber Unfortunately, the power to the Q2 septum magnet near this chamber did not get turned off before the water to the magnet was shut off (40 kW)

7 PEP Status M. Sullivan MAC Review Nov , 2007 Q2 magnet The magnet coils heated up and damaged the insulation. The power supply finally tripped on a ground fault. We had a failure of three systems/procedures at the same time that caused this magnet to overheat We have improved our procedures and fixed the hardware so that this can not happen again We did have a spare set of magnet coils for this magnet We lost an extra week in May removing and replacing the coils in the Q2 magnet

8 PEP Status M. Sullivan MAC Review Nov , 2007 Side view of BaBar Q2 magnet

9 PEP Status M. Sullivan MAC Review Nov , 2007 The front end of Q2

10 PEP Status M. Sullivan MAC Review Nov , 2007 Removing the Top of Q2

11 PEP Status M. Sullivan MAC Review Nov , 2007 The top half being lifted out

12 PEP Status M. Sullivan MAC Review Nov , 2007 The bottom of Q2

13 PEP Status M. Sullivan MAC Review Nov , 2007 Removing the bottom half of Q2 Many, many thanks go to all the support groups and people including the BaBar people who made it possible for us to recover from this in a safe and timely manner.

14 PEP Status M. Sullivan MAC Review Nov , 2007 Run 6 History (2) In June and July we went into the ring on three separate occasions to replace flex flange RF seals that we had identified as causing a large number of beam aborts In spite of these difficulties we managed to break most of our luminosity records From mid July to the end (Sept. 4) we ran more reliably (very little down time, although the beam abort rate was still high) Sullivan

15 PEP Status M. Sullivan MAC Review Nov , 2007 Flex flange RF seal Silver vapor from plated washer Molten Cu Cu vapor

16 PEP Status M. Sullivan MAC Review Nov , 2007 MDs We had several MDs –In April we installed PM skew quads into the LER to compensate the coupling from the BaBar solenoid before reaching the arcs. This allows us to lower the LER vertical emittance. –In mid July we tried to close the abort gap. This would make the phase transient equal and zero for both rings. We found we could not close the gap much more than the value we currently run at without making the HER unstable which we think is due to trapping too many ions. –Coupling MD to try to lower the LER coupling –In August we tested the HER 90 deg lattice. The test was very successful and we plan to install the 90 deg lattice into the HER in early January. –We also had a beam-beam MD where we increase the beam bunch current with a subset of the total bunches –We had several RF MDs to try to raise the beam currents Wittmer Wienands Wittmer

17 PEP Status M. Sullivan MAC Review Nov , 2007 New Skew Magnets to Improve LER Vertical Emittance  10 to 50% gain at fixed currents Physicist design (F-J. Decker)

18 PEP Status M. Sullivan MAC Review Nov , x Run 6 nos.

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22 PEP Status M. Sullivan MAC Review Nov , 2007 Downtime Activities Install the last of the new LER bpms Replace all of the HER flex flange RF seals IR2 straight –Install the repaired HER Q4 chamber –Install the two new LER Q5 chambers –Replace a leaky HER frangible link –Replace 5 bellows in the HER with HOM absorbing bellows –Replace 12 LER bellows with HOM absorbing bellows Replace a ceramic window in RFS 12-1A cavity Replace the horizontal transverse kicker in the LER Done >85% Done Done

23 PEP Status M. Sullivan MAC Review Nov , 2007 HOM absorbing bellows Absorbing tiles Novokhatski Weathersby Kurita Reeck Metcalfe In IR 2 we are replacing 5 bellows sections in the upstream LER and HER and 7 units in the downstream LER with bellows modules that contain HOM absorbing tiles. We hope to reduce the HOM power in this area

24 PEP Status M. Sullivan MAC Review Nov , 2007 HER upstream beam line NEGs Good screens Weak screens

25 PEP Status M. Sullivan MAC Review Nov , 2007 LER upstream beam line Absorber NEG Fixed collimator

26 PEP Status M. Sullivan MAC Review Nov , 2007 LER downstream beam line SR mask First bpms that dropped in this area

27 PEP Status M. Sullivan MAC Review Nov , 2007 Beam aborts In February we lost the beam 229 times (about 8.8 losses each running day) In August we lost the beam 263 times (about 8.8 losses each day) Each beam abort is about 30 min of lost integrated lumi RF aborts are a significant fraction of the total abort rate (about 2.4 losses a day) The largest single category of aborts is from an unstable HER beam usually related to a vacuum spike. We believe most of these are from failing RF seals. Bertsche, Van Winkle DeBarger, Sullivan

28 PEP Status M. Sullivan MAC Review Nov , 2007 Luminosity Peak The avenues we see for improving the peak luminosity are: –Shorten the beam bunches –Lower beta Y* –Increase the beam currents –Improve the vertical beam emittance

29 PEP Status M. Sullivan MAC Review Nov , 2007 Luminosity Integration The avenues we see for improving the integrated luminosity are: –Reduce the number of beam aborts –Increasing the peak lumi helps as well as long as the abort rate does not increase too much

30 PEP Status M. Sullivan MAC Review Nov , 2007 Startup Plans Start up with the saved machine from Sept. (60 deg lattice for the HER) Raise the LER RF voltage from 4.05 MV to 4.5 MV. We have already run at this voltage for over two months in run 5. Scrub the rings and start delivery before Christmas Attempt to install the 90 deg lattice in early January as soon as we have high currents in the rings

31 PEP Status M. Sullivan MAC Review Nov , 2007 Overall run 7 plan Get to peak performance as soon as we can –All major MDs early in the run –Discover our limits quickly – being careful! Very few small MDs after April 1. We will still want to characterize the machine regularly (2 hrs every other week) Steady running as soon as we can with gradual improvements (tuning, raising currents if possible, etc.) We must keep a close eye on our delivery efficiency. Too many beam aborts can really hurt.

32 PEP Status M. Sullivan MAC Review Nov , 2007 LER RF 4.5 MV HER RF 16.5 MV Delivery starts as soon as we get to about 4 x with high but acceptable backgrounds Lumi goal of 8 x10 33

33 PEP Status M. Sullivan MAC Review Nov , 2007 Put in 90 deg lattice and try very hard to make it stick Raise LER RF to 5 MV Lower β y *s Raise HER RF to 17 MV if the above did not stick Emittance tuning Lumi goal of 11 x10 33

34 PEP Status M. Sullivan MAC Review Nov , 2007 Try to get in the HER 90 deg lattice again Continue to raise beam currents Raise HER RF to 17.5 MV Lumi goal of 13 x10 33 Raise LER RF to 5.5 MV? Lower β y *s

35 PEP Status M. Sullivan MAC Review Nov , 2007 Continue to raise beam currents Raise HER RF to 18.0 MV? Lumi goal of 15 x10 33 Lower β y *s Emittance tuning Continue optics studies

36 PEP Status M. Sullivan MAC Review Nov , 2007 MDs Some MDs planned –Install 90 deg lattice early to see if we can run with it –Specific attempts to improve the coupling in the LER –Lower the β y * s – may try this during delivery but then will want to measure results –Specific attempts to increase beam currents (RF and feedback MDs)

37 PEP Status M. Sullivan MAC Review Nov , 2007 Running off the 4S We expect BaBar to want to run off resonance for some of the time as usual The collaboration is also considering running somewhere other than the 4S resonance for some fraction of the time –A possible candidate is the 3S –We have run on the 3S briefly in 2002 doing a quick energy scan (24 hr). We lowered the HER beam energy. –Running on the 3S for some time should not be at all difficult. It was easy to get to the 3S Ecm. –Another candidate is the 2S –Although we have not lowered the HER beam energy that far we do not anticipate an difficulties is being able to do so We will want to schedule any off resonance running once we find out what the collaboration wants to do (not too early and not too late)

38 PEP Status M. Sullivan MAC Review Nov , 2007 Summary Although Run 6 had a slow start we did manage to break most of our luminosity records We uncovered a major problem with the flex flange RF seals in the HER and are addressing this issue this downtime. We are certain this will reduce the beam abort rate. The permanent magnet skew quads for the LER were installed and although we have seen some luminosity improvement we are hopeful we can gain more from this upgrade We have ambitious luminosity goals for Run 7. Shortening the beam bunches will let us lower β y *s. That and raising beam currents are our two major plans for increasing the peak lumi. Reducing the number of beam aborts is the other half of the plan to increase integrated lumi numbers. We will have to be cautious in our attempts to increase peak lumi. A close watch over temperatures and vacuum will be needed as we shorten bunches and increase currents on our push for a higher peak We look forward to getting this machine to really perform before we turn off next October