IR2 and IR4 Summary PEP-II meeting Jan. 23, 2006 M. Sullivan.

IR2 and IR4 Summary

PEP-II meeting

Jan. 23, 2006

M. Sullivan

• Tues of last week we opened up the vacuum in regions 4 and 2 to look for sources of arcing

• Region 4 had a very clear source of arcing from an RF gap ring that had partially fallen into the beam aperture– We found 2 cases where the gap ring was not

properly positioned– After making sure about the gap and gap ring

dimensions the system was put back together Friday– Discovered a vacuum leak in a water tube joint that

was repaired with welding but then we uncovered another leak on the other water tube joint

– Ended up replacing the pump tee with another unit Sunday day shift

• Region 2 was searched initially on the forward side of the detector and no obvious trouble was found– First looked from outside the LER frangible link all the

way down to the IP Be beam pipe (20 cm from the IP)– The IP bellows and what we could see of the Q1/Q2

bellows looked fine– Upon coming back out from the IP bellows we noticed

an RF seal that didn’t look the same as the other seals at the Q2/Q4 pipe junction (picture)

– In the borescope the surface looked like it might be pitted

– We took apart the beam line up to this joint and after removing the seal found no obvious problem (no signs of discoloration or of arcing)

Interaction Region Layout

LER HER

7039 gauge

SIG11LER sensitive

2187 gauge

3044 pump

LER frangible link

Detector

7043 pump

8020 pump

3027 gauge

Support tube end bellows

3027 pump

NEG pump

Backward Q2 NEG

Forward Q2 NEG

• With the beam line apart up to this joint we able to completely look at the Q1/Q2 bellows and still found nothing wrong

• We did find that the vacuum gasket had been pinched in the Q2/Q4 junction

• Decided to put the beam line back together but also borescope the forward side HER chamber as far as we can and to borescope the backward LER chamber

• In the forward side HER beam line, we actually managed to get the borescope all the way down to the Q2/Q4 seal on the HER beam pipe in order to make sure that that seal was ok as well as all the seals from there on out including the frangible link

• We also borescoped in from the backward side LER beam line and found something we don’t like but that we decided to try to run with as is and not fix the problem right now

• The RF seal around one of the flange pairs in the Q1/Q2 bellows has 5 fingers that are not properly seated (picture)

• This bellows section is very hard to get to. It is inside the DIRC tunnel and many SVT cables as well as water, air lines and power cables have to be removed in order to get to this bellows.

• We have regenerated the NEG pumps in region 2 and the pressure is coming down nicely (pictures)

• We have replaced the LER frangible link on the forward side with new spare bellows (some fingers were displaced and/or not engaged in the old unit)

• We have moved the RGA that was at 3056 to the 3027 location in the incoming LER

• We will need to scrub for at least a couple of days but perhaps we can start delivering luminosity in the near future

Pressure at the 3054 pump

Pressure at the 3044 pump

Pressure at the 3027 pump. At this time, the TSP in this location had not yet been flashed.