August 4-5, 2004 PEP-II Post Run 4 Review 1 M. Sullivan PEP-II Post Run 4 Review August 4-5, 2004 IR Summary and Issues

August 4-5, 2004 PEP-II Post Run 4 Review 2 Outline Summary Issues Conclusions

August 4-5, 2004 PEP-II Post Run 4 Review 3 PEP-II Interaction Region and the BaBar Detector HER LER Collision point BaBar ee ee

August 4-5, 2004 PEP-II Post Run 4 Review 4 Summary We have achieved  y * s of 10 mm With  x * s of 30 cm Total beam currents of 2450 on 1550 (1590 on 2540 on last shift) No sign of SR backgrounds Total current in the support tube up to 4.1 A! Heating in the IR (from Q2 to Q2) OK so far Discovered NEGs being heated by HOM power Stan will talk about this

August 4-5, 2004 PEP-II Post Run 4 Review 5 Issues Run 5 goals that affect the IR LER current of 3.3 A HER current of 1.8 A Higher bunch currents  more HOM power Shorter LER bunch length  more HOM power Lower  y * s to 9 mm Lower LER  x * to 30 cm Increase LER emittance to 50 nmrad BSCs NEGs Total of 5.1 A !

August 4-5, 2004 PEP-II Post Run 4 Review 6 BSCs Present machine parameters LER  x * = 30 cm and LER  x = 22 nmrad LER  x * may be a little low, but it is the value for run 5 BSC just clears the present Q2 chamber on the forward side Plenty of room on the backward side

August 4-5, 2004 PEP-II Post Run 4 Review 7 BSCs Expected LER beam size for run 5 LER parameters:  x * = 30 cm  x = 50 nmrad BSC is defined as 15  + 2mm (uncoupled) BSC violated at the septum Just enough room for the beam New chamber being built for summer 2005

August 4-5, 2004 PEP-II Post Run 4 Review 8 Summary of the NEG story When we regenerated the NEGs in IR2 on March 24 we began to wonder if some of the NEGs were starting to heat up from HOM power. We confirmed that some were getting hot shortly thereafter but we did not get a full picture until the next ROD on June 3 when we instrumented every NEG in the upstream LER beam line. Regeneration temperature is about 750 °F

August 4-5, 2004 PEP-II Post Run 4 Review 9 Lab test data of NEG outgassing as a function of temperature LER NEG Pump Temperatures Upstream LER side 350 °F

August 4-5, 2004 PEP-II Post Run 4 Review 10 Data from the two hottest NEGs NEG temperatures Pump pressure of The ion pump is between the two NEGs

August 4-5, 2004 PEP-II Post Run 4 Review 11 Recent test NEG data We held the test NEG at our regen temperature for a month

August 4-5, 2004 PEP-II Post Run 4 Review 12 LER upstream NEG work This summer: –Take out the nine NEGs with “c type” screens and install a small HOM absorber in each cavity –The total length of NEG pumping that will be removed is 5.5 m out of a total of 40.4 m –We will remove the Q4 NEG and replace it with a HOM absorber (another 1.6 m) –We then add extra pumping at the port between the Q4 and Q5 chambers –In addition, we will add extra screening to the ion pumps in this region

August 4-5, 2004 PEP-II Post Run 4 Review 13 Aside: Vacuum model We have started building a vacuum model of straight 2 Had great help getting started by a summer student (Edward Young) We have a preliminary model of the LER upstream beam pipe Still need to work on screen conductances and on outgassing values from SR fans Nevertheless we can get some idea about what happens when the above LER NEGs are removed

August 4-5, 2004 PEP-II Post Run 4 Review 14 Upstream LER Ideal Abstracted from Edward’s presentation LER beam line from Q2 septum to about 63 m upstream

August 4-5, 2004 PEP-II Post Run 4 Review 15 Upstream LER after summer down Abstracted from Edward’s presentation

August 4-5, 2004 PEP-II Post Run 4 Review 16 HER Upstream Q5 chamber We plan to replace this chamber BaBar Deadtime Diamond BW (HER) NEG temp in Q5 chamber

August 4-5, 2004 PEP-II Post Run 4 Review 17 Other upstream HER NEGs and heater instrumentation The upstream HER beam pipe is also blanketed with NEG pumps starting at 21 m and going up to up to about 45 m from the IP There are a total of 4 vacuum chambers in this region with NEG pumping (6 long NEGs). All of the pumps are below the beam chamber. The collimator at 35 m has a TSP The only chamber in this area without pumping is the fast kicker chamber The screen is very similar to the “c type” screen seen in the LER Stan instrumented one of these NEG heaters the last week (they all look like they have the same design) by putting a small current (10 mA ) through the heater circuit and measuring the heater resistance Next slide

August 4-5, 2004 PEP-II Post Run 4 Review 18 HER upstream NEG screen This is a post at the center of the chamber

August 4-5, 2004 PEP-II Post Run 4 Review 19 NEG heater temperature through heater resistance (work in progress) Stan has installed a circuit that measures some of the heater rod resistances He has instrumented: –LER upstream Q4 + Q5 (same circuit) BV1 + next outboard (3042) (same circuit) –HER Q5 downstream Q5 upstream BLF upstream

August 4-5, 2004 PEP-II Post Run 4 Review 20 Temperature plot of first “c” chamber in LER (BV1) Temperature plot of first “c” chamber in LER (BV1) using resistance measurement Agreement is no better than about 20%. The signal is complicated by the resistance being the sum of the leads plus another NEG heater BV1 NEG

August 4-5, 2004 PEP-II Post Run 4 Review 21 Q5 NEGs Q5 downstream Q5 upstream The upstream Q5 NEG resistance matches the TC we have in that NEG Conclusion: Downstream HER Q5 NEG is hotter than the upstream HER Q5 NEG

August 4-5, 2004 PEP-II Post Run 4 Review 22 Upstream HER BLF NEG This NEG is located m from the IP So far, this NEG looks OK We should be OK for run 5 We need to instrument all of these upstream NEGs especially the ones closest to the collimator

August 4-5, 2004 PEP-II Post Run 4 Review 23 Conclusions The run 5 beam parameters will fill more of the IR aperture, especially for the LER HOM power in IR2 will go up We will violate the LER BSC (as defined) on the upstream septum This summer we will try to fix as many of the NEG heating problems as we can –9 LER “ c type ” chambers will be modified –The upstream LER Q4 chamber will be modified –The two LER upstream movable collimators will be removed –Hope to replace the HER upstream Q5 chamber These fixes should make recovering from a NEG regen much faster The upstream HER NEGs will need to be watched more closely