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IR vacuum

IR vacuum. M. Sullivan PEP-II meeting Feb. 22, 2007. Status. We have recently seen a decrease in luminosity as the HER beam current is increased The time scale is sometimes slow (minutes) and looks like a gas pressure increase We saw this last year when we studied the problem in IR2

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IR vacuum

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  1. IR vacuum M. Sullivan PEP-II meeting Feb. 22, 2007

  2. Status • We have recently seen a decrease in luminosity as the HER beam current is increased • The time scale is sometimes slow (minutes) and looks like a gas pressure increase • We saw this last year when we studied the problem in IR2 • A 30 nT pressure bump in the Q5 magnet reduces the luminosity by blowing up the vertical size of the HER

  3. Pressure rise from heating Q5 NEG pump last year Pressure rise at 8020 gauge is about 30 nTorr

  4. More Status • We presently see a pressure rise with beam current at pressure gauge 8027 in the downstream HER • Difficult to see in the pumps because of electron current when we have bem in the machine • However, With no beam in the machine…

  5. Event after beam abort of yesterday morning 8027 gauge 8025-8026 pump 8020 gauge 8023-8024 pump 8027-8028 pump 8029 pump 8020 pump 8032-8043 pump

  6. Layout of the Area Pressures at the peak of the bump after the beam abort 2 72 4.5 2.5 0.8 3 8027g 8020g 8028 8027 8026 8025 8024 8023 8022 8020 Frangible link High power downstream dump 8029-8043 HER

  7. Picture of the end of the HPDD

  8. Pressure History of 8027g Since the start of Run 6 August 1-15 2006

  9. Summary • It looks like we have a leak at or near the end of the HPDD • The gauge at 8027 reads the highest and is a reliable measure even with beam (it is screened) • The gauge reads at least 50 nTorr with beam (with spikes and high spots of 200 nTorr) which is the right range of pressure to cause a luminosity drop • We have also seen cases where the pressure suddenly increases with steady beam currents

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