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Observations on background in ALFA for β * = 1000 m MD

Observations on background in ALFA for β * = 1000 m MD. 15-10-2012. Sune Jakobsen on behave of the ALFA community. Background study in ALFA Background study in ATLAS Conclusions.

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Observations on background in ALFA for β * = 1000 m MD

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  1. Observations on background in ALFA for β* = 1000 m MD 15-10-2012 Sune Jakobsen on behave of the ALFA community

  2. Background study in ALFABackground study in ATLAS Conclusions Background study in ALFA (Beam 2) Move all B7L1U to 4 σNominal Step out 1000 µm with C6R7 Moving out Roman Pots Move all ALFA Roman Pots to 10 σNominal Move all B7L1L to 4 σNominal Step out 100 µm with C6R7 Reference Step out 100 µm with C6R7 Step out 100 µm with D6R7 Step out 1000 µm with D6R7 Scrape one jaw of TCPs in IP7 to 2 σNominal Rate in ALFA detectors TCP.C6R7.B2 (vertical) Primary collimators TCP.D6R7.B2 (horizontal) XRPV.A7L1.B2 ALFA Roman Pots XRPV.B7L1.B2 NIELS BOHR INSTITUTE UNIVERSITY OF COPENHAGEN 2/5 Observations on background in ALFA for β* = 1000 m MD Sune Jakobsen

  3. Background study in ALFABackground study in ATLAS Conclusions Observations on background in ALFA Background again very high on beam 2 for ALFA (beam 1 for TOTEM). Very large background at 4σnominal even with primary collimators at 2σnominal Huge reduction in background observed when move out both plan of primary collimators (up to factor 40). Repopulation speed depending steep size. First 100 µm step with C6R7: rate 9800 Hz and increasing by 1850 Hz/minute (19 %) Second 100 µm step with C6R7: rate 4200 Hz and increasing by 425 Hz/minute (10 %) 1000 µm step with C6R7: rate 720 Hz and increasing by 230 Hz/minute (30 %) NIELS BOHR INSTITUTE UNIVERSITY OF COPENHAGEN 3/5 Observations on background in ALFA for β* = 1000 m MD Sune Jakobsen

  4. Background study in ALFA Background study in ATLAS Conclusions Background study in ATLAS (Beam 2) Move all B7L1U to 4 σNominal Move all B7L1L to 4 σNominal Step out 1000 µm with C6R7 Moving out Roman Pots Move all ALFA Roman Pots to 10 σNominal Step out 100 µm with C6R7 Reference Step out 100 µm with C6R7 Step out 100 µm with D6R7 Step out 1000 µm with D6R7 Scrape one jaw of TCPs in IP7 to 2 σNominal Rate in ALFA detectors TCP.C6R7.B2 (vertical) Primary collimators TCP.D6R7.B2 (horizontal) XRPV.A7L1.B2 ALFA Roman Pots XRPV.B7L1.B2 NIELS BOHR INSTITUTE UNIVERSITY OF COPENHAGEN 4/5 Observations on background in ALFA for β* = 1000 m MD Sune Jakobsen

  5. Background study in ALFA Background study in ATLAS Conclusions Conclusions Background again very high on beam 2 for ALFA (beam 1 for TOTEM). Very large background at 4σnominal even with primary collimators at 2σnominal. Scraping and then retracting the primary collimators effectually reduces the background, but only proven for positions that will not be allowed during data taking. Repopulation speed depending step size. Further studies needed and preferably a collimator solution which does not imply any movement/interruptions during data taking. NIELS BOHR INSTITUTE UNIVERSITY OF COPENHAGEN 5/5 Observations on background in ALFA for β* = 1000 m MD Sune Jakobsen

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