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Improvements in Vacuum Levels at F11 and Impact on CDF Proton Halo Losses

The FNAL TeV Halo Meeting on July 3, 2002, reviewed vacuum conditions at F11 and their effects on proton halo losses in CDF. Prior to ferrite rod replacement, pressure and loss rates showed significant fluctuations with rising intensities. After replacing the ferrite rods, pressure decreased, stabilizing loss rates. Simulation results indicated average pressures were much lower than expected, and outgassing rates were about one-fourth of predictions. This suggests that conditions at Interaction Points are better than previously assessed, dispelling concerns about them being "hot spots" for poor vacuum.

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Improvements in Vacuum Levels at F11 and Impact on CDF Proton Halo Losses

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  1. Vacuum at F11 and the Interaction Points Ron Moore FNAL TeV Halo Meeting – 3 July 02

  2. F11 vacuum and CDF proton halo losses – store 1289 before ferrite replacement @ F11 pressure and losses rise and fall p intensity F11 pressure CDF PHSM CDF LOSTP

  3. F11 vacuum and CDF proton halo losses– store 1486 after ferrite replacement @ F11 pressure reduced, no dramatic rise losses do not rise F11 temperature F11 pressure CDF LOSTP

  4. D0 Pressure Profile FromMike McGee’s Simulation One half of IR D0IG01 pressure 2.4*10-9 torr Average pressure = 1.26*10-8 torr

  5. CDF Pressure Profile FromMike McGee’s Simulation One half of IR B0IG01 pressure 2.5*10-10 torr Average pressure = 1.22*10-8 torr

  6. D0 outgassing rate measured = 7.3*10-9 torr*liter/sec expected = 29*10-9 torr*liter/sec CDF outgassing rate measured = 7.1*10-9 torr*liter/sec expected = 29*10-9 torr*liter/sec Both outgassing rates 1/4 the expected rates

  7. Summary • Replacing ferrite rods improved vacuum @ F11 and eliminated CDF proton loss bump • Expected average pressure @ IPs  1.2*10-8 torr • But, measured outgassing rates are 1/4 expected • Models are being reexamined • Vacuum at IPs likely better than initially believed • IPs are not “hot spots” of poor vacuum R. Moore - FNAL

  8. Proton halo over past 4 months Proton loss rates from experiments divided by narrow-gate intensity D0 CDF

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