1 IR NEG heating M. Sullivan MAC Review Dec , 2004 M. Sullivan Machine Advisory Committee Review December 13-15, 2004 IR NEG Heating and Upgrade

2 IR NEG heating M. Sullivan MAC Review Dec , 2004 Outline History from last run Summer work Vacuum model Conclusions

3 IR NEG heating M. Sullivan MAC Review Dec , 2004 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. MAC Review in April 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

4 IR NEG heating M. Sullivan MAC Review Dec , 2004 Upstream LER plan view 136F side 160F side 150F bot 130F bot 150F bot 150F bot Collimators Quad chambers Dipole chambers 268  F 425  F 453  F 724  F LER current 2.2 A

5 IR NEG heating M. Sullivan MAC Review Dec , 2004 Collimator 724  F 268  F 453  F

6 IR NEG heating M. Sullivan MAC Review Dec , 2004 Lab test data of NEG outgassing as a function of temperature LER NEG Pump Temperatures Upstream LER side 350 °F

7 IR NEG heating M. Sullivan MAC Review Dec , 2004 Data from the two hottest NEGs NEG temperatures Pump pressure of The ion pump is between the two NEGs

8 IR NEG heating M. Sullivan MAC Review Dec , 2004 LER NEG Test chamber

9 IR NEG heating M. Sullivan MAC Review Dec , 2004 Test NEG data over the summer We held the test NEG at our regen temperature for a month with a Turbo pump attached

10 IR NEG heating M. Sullivan MAC Review Dec , 2004 Pressure in the test NEG Pressure as a function of time in the test NEG. Holding the NEG at the regen temperature of 725  F (400  C). After the first 6 hrs After about 48 hrs

11 IR NEG heating M. Sullivan MAC Review Dec , 2004                     Hydrogen Concentration Torr l/g Hydrogen Equilibrium Pressure (Torr) 200° C 300° C 400° C 600° C 500° C St707 Embrittlement Limit (20 Torr l/g) NEG heaters on NEG heaters off Ion pumps off Ion pumps on Heat NEGs for 1 hr degC Time 11:45-12:45 Tubro cart pump: 220 L/s Pressure at pump about Torr Some regeneration details

12 IR NEG heating M. Sullivan MAC Review Dec , 2004 LER upstream NEG work This summer: –We took out the nine NEGs with “c type” screens and installed a small HOM absorber in each cavity –The total length of NEG pumping that was removed is 5.5 m out of a total of 40.4 m –We removed the two movable collimators –We removed the Q4 NEG and have replaced it with a HOM absorber (another 1.6 m of pumping) –We have added extra pumping at the port between the upstream LER Q4 and Q5 chambers –In addition, we have added extra screening to the ion pumps in this region

13 IR NEG heating M. Sullivan MAC Review Dec , 2004 Existing 3082 chamber BPM Chamber support Cooling bar NEG plenum NEG heater Quad extrusion

14 IR NEG heating M. Sullivan MAC Review Dec , 2004 Chamber shown inverted and plenum not shown for clarity SiC HOM absorber

15 IR NEG heating M. Sullivan MAC Review Dec , 2004 Part of one of the NEG pumps that was removed this last summer

16 IR NEG heating M. Sullivan MAC Review Dec , 2004 One of the collimators that was removed The NEG in this chamber was one of the hottest

17 IR NEG heating M. Sullivan MAC Review Dec , 2004 HOM absorber to replace NEG pump

18 IR NEG heating M. Sullivan MAC Review Dec , 2004 Drawing of installed extra pumping

19 IR NEG heating M. Sullivan MAC Review Dec , 2004 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 check on screen conductances and on outgassing values from SR fans Nevertheless we can get some idea about what happens to the vacuum pressure profile with the above LER NEGs removed

20 IR NEG heating M. Sullivan MAC Review Dec , 2004 Chamber Model Layout HER downstream LER upstream LER downstream HER upstream Support chamber Q5 NEG m m ST plot plot

21 IR NEG heating M. Sullivan MAC Review Dec , 2004 Support tube Vacuum Design Model Vacuum pressure in the support tube. The model predicts a pressure peak at the IP of about 20 nTorr.

22 IR NEG heating M. Sullivan MAC Review Dec , 2004 No radial ion pumps We lost these pumps a couple of years ago. One developed an Argon instability before it died. Both pumps do not work right now. We intend to replace these pumps during the next downtime.

23 IR NEG heating M. Sullivan MAC Review Dec , 2004 Upstream LER Ideal LER beam line from Q2 septum to about 63 m upstream

24 IR NEG heating M. Sullivan MAC Review Dec , 2004 Upstream LER after summer down

25 IR NEG heating M. Sullivan MAC Review Dec , 2004 HER scrubbing

26 IR NEG heating M. Sullivan MAC Review Dec , 2004 HER Upstream Q5 chamber We plan to replace this chamber BaBar Deadtime Diamond BW (HER) NEG temp in Q5 chamber

27 IR NEG heating M. Sullivan MAC Review Dec , 2004 The upstream HER NEGs and heater instrumentation The upstream HER beam pipe is also blanketed with NEG pumps starting at 21 m and going out 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 screen is very similar if not identical to the “c type” screen seen in the LER The collimator at 35 m has a TSP The only chamber in this area without pumping is the fast kicker chamber

28 IR NEG heating M. Sullivan MAC Review Dec , 2004 HER upstream NEG screen This is a post at the center of the chamber

29 IR NEG heating M. Sullivan MAC Review Dec , 2004 NEG heater temperature through heater resistance Stan Ecklund 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 This particular NEG pump can not be instrumented any other way

30 IR NEG heating M. Sullivan MAC Review Dec , 2004 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

31 IR NEG heating M. Sullivan MAC Review Dec , 2004 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

32 IR NEG heating M. Sullivan MAC Review Dec , 2004 Upstream HER BLF NEG This NEG is located m from the IP So far, this NEG looks OK We think we will be OK for run 5 We have instrumented all of these upstream NEGs with TCs

33 IR NEG heating M. Sullivan MAC Review Dec , 2004 Conclusions We have fixed the NEG pumps in the upstream LER beam pipe that were getting the hottest by removing the pumps and installing a HOM absorber in the pump cavity We removed the NEG pump that was closest to the septum chamber because HOM power was also heating up that pump and installed a HOM absorber in its place We removed the two movable collimators The run 5 beam parameters will increase the HOM power we have so far experienced by increasing the beam currents and shortening the bunches HOM power in IR2 will go up We have instrumented the upstream HER NEGs and we will be watching them very carefully during this coming run