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Current Background Situation in BaBar

Current Background Situation in BaBar. “Always a concern, often an issue but never a showstopper” The background sources: (Synchrotron Radiation), Beam-Gas, Radiative Bhabbas , Beam-Beam effects, Radiation bursts, Injection, (Touscheck) The background effects:

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Current Background Situation in BaBar

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  1. Current Background Situation in BaBar “Always a concern, often an issue but never a showstopper” • The background sources: (Synchrotron Radiation), Beam-Gas, Radiative Bhabbas , Beam-Beam effects, Radiation bursts, Injection, (Touscheck) • The background effects: integrated dose, instantaneous damage, operational issues, data quality • The background remediation strategy Babar protection system, budget policy, forward looking to bottlenecks using projection and simulations • Today’s questions • Trickle injection • Injection quality • Preparation for tomorrow • Conclusion Guy Wormser, Super B-Factory Workshop, Jan 04

  2. The background sources • Synchrotron radiation : very well masked, has never been a problem for BABAR • Beam-Gas : BABAR sees debris from electromagnetic showers of scattered electrons and photons. • Two subcomponents : Brems and Compton scattering • Well described by simulation • Efficient collimator scheme Guy Wormser, Super B-Factory Workshop, Jan 04

  3. The background sources (2) • Radiative Bhabbas • Showers debris from off-energy electrons or positrons after Bhabbas scattering swept away by magnetic elements in interaction regions • Beam-beam effects • « Trapped/Dust events » (HER specific) • Touschek effects : not observed yet Guy Wormser, Super B-Factory Workshop, Jan 04

  4. Predictability score • Predictables sources • Synchrotron • Beam gas • Bremstralhung • Compton • Touschek • In principle predictable source • Radiatvie Bhabbas • Unreliably predictable sources • Beam-beam • Electron cloud effects • Injection doses • Unpredictable sources • Radiation bursts, “dust events” Guy Wormser, Super B-Factory Workshop, Jan 04

  5. Agressive PEP-II plans Can BABAR keep up? Present headroom limited! Historically, the same challenge has always been met! Guy Wormser, Super B-Factory Workshop, Jan 04

  6. Background parametrization based on February 2002 data The observed background is roughly twice larger than the sum of the single beam contributions Guy Wormser, Super B-Factory Workshop, Jan 04

  7. M. Kelsey DCH background history Guy Wormser, Super B-Factory Workshop, Jan 04

  8. Serious problem in DCH readout if nothing is done Guy Wormser, Super B-Factory Workshop, Jan 04

  9. Remediation and Forward looking of bottlenecks • Example of DIRC TDC • In 1999, we predicted that the single rate PMT in the DIRC would in 2002-2003 exceed the 200 kHz limit • A lot of effort to improve the shiedling • Launch design of a new TDC, implemented in summer 2002 with a 2 MHz capability. • The 200 kHz limit was indeed reached in fall 2002 • Next on line: DCH read out! Guy Wormser, Super B-Factory Workshop, Jan 04

  10. DIRC main source of background: Radiative Bhabhas striking Q4 magnet inboard flange • Source discovered empirically with a Geiger counter. • Shielding erected step-by-step slowly building empirically a proof that things are improving. • A final shield erected in 2001, and the whole job completed in 2002. • Carsten proved later, with a Turtle program, that a major source of DIRC background is the radiative Bhabhas striking Q4 inboard flange, which is too small. Guy Wormser, Super B-Factory Workshop, Jan 04

  11. IFR issues • IFR is the only BABAR subdetector where the existing hardware capabilities are presently significantly degraded because of background: Layers 13, 15,16 turned off in the forward endcap (loss of factor ~2 in the mu/pi rejection in that region) IFR background comes losses near collimator BSC3042 which is very sensitive to beam-beam effects and thus very useful to the rest of BABAR… Must provide a shielding wall (summer 2004) Guy Wormser, Super B-Factory Workshop, Jan 04

  12. IFR issues Guy Wormser, Super B-Factory Workshop, Jan 04

  13. IFR and beam loss monitor Guy Wormser, Super B-Factory Workshop, Jan 04

  14. SVT Background from HER HER sensitive SVT module (Does not have threshold shift problem): (BW:MID) Background almost doubled after move to half-integer Again it has come down a bit during run-4 Note peak occupancy is 150% higher than average occupancy! Moves toward half-integer For occupancies in all SVT modules, see: http://www.slac.stanford.edu/~babarsvt/SectionOccupancies.ps Guy Wormser, Super B-Factory Workshop, Jan 04

  15. SVT rates in 2003 compared to 2002 extrapolation Guy Wormser, Super B-Factory Workshop, Jan 04

  16. Single beam and lumi sensitivity Guy Wormser, Super B-Factory Workshop, Jan 04

  17. MID Plane Doses Stable beam contribution of FW:MID and BW:MID is overestimated Damage in SVT modules starts Run 3+4 dose is 40-60% of Run1+2 Luminosity is 55% of Run1+2 Guy Wormser, Super B-Factory Workshop, Jan 04

  18. TOP Doses Dominated by injection dose (up to 90%) Getting HER to “trickle quality” would provide large gains Guy Wormser, Super B-Factory Workshop, Jan 04

  19. Summary of Detector sensivities and main issues • SVT : Integrated Dose, Occupancy, single beam and beam-beam, FE electronics strange effects • DCH : Readout capabilities, radiative Bhabbas • DIRC : No problem for now, radaitive Bhabbas • EMC Integrated dose in Endcap for the long term, leakage current in Diodes (neutrons?), occupancy, • IFR Single rate for external layers, beam-beam effects • SVTRAD : integrated dose, will need to be replaced soon • Integrated dose: SVT 2Mrad in the most exposed regions, EMC 1 krad in the most exposed regions • Rather similar to what BELLE received ? Guy Wormser, Super B-Factory Workshop, Jan 04

  20. MID Dose Rates until 2009 Use Seeman model for beam currents to predict dose rates: Dose rates do not looking forbiddingly high Rates peak at roughly the current soft abort limits - DQ should still be reasonable Guy Wormser, Super B-Factory Workshop, Jan 04

  21. Midplane Doses until 2009 • Module exchange in 2005 looks well timed with 4 Mrad budget • One rotation in 2007 should be able to keep MID modules installed in 2005 below 5 Mrad A rotation will move the high dose in FE:MID to other module Guy Wormser, Super B-Factory Workshop, Jan 04

  22. BABAR scorecard July 2004 Guy Wormser, Super B-Factory Workshop, Jan 04

  23. BABAR scorecard July 2006 Guy Wormser, Super B-Factory Workshop, Jan 04

  24. Dose in calorimeter Guy Wormser, Super B-Factory Workshop, Jan 04

  25. BABAR scorecard 2009 Guy Wormser, Super B-Factory Workshop, Jan 04

  26. Data quality issues in SVT Guy Wormser, Super B-Factory Workshop, Jan 04

  27. Resolution degration with occupancy Guy Wormser, Super B-Factory Workshop, Jan 04

  28. Example in Guy Wormser, Super B-Factory Workshop, Jan 04

  29. HER Injection Problems Guy Wormser, Super B-Factory Workshop, Jan 04

  30. Characterization of injection aborts/inhibits BP / LP + ODF Guy Wormser, Super B-Factory Workshop, Jan 04

  31. B. Petersen G. Wormser A variety of fast radiation spikes (stored beams) Guy Wormser, Super B-Factory Workshop, Jan 04

  32. B. Petersen G. Wormser A variety of fast radiation spikes (stored beams) Guy Wormser, Super B-Factory Workshop, Jan 04

  33. Run 4 Trip Summary Average of 4 trips/day – Run 3 average was 3 trips/day A couple of aborts are due to broken thermistor Only one other abort looked suspicious Last two weeks average is down to almost 1 trip/day Guy Wormser, Super B-Factory Workshop, Jan 04

  34. Some exemple of « Dust events » Guy Wormser, Super B-Factory Workshop, Jan 04

  35. Trickle solved top of fill beam_beam effects Guy Wormser, Super B-Factory Workshop, Jan 04

  36. Revided simulation efforts • Locations of the sources of Lumi terms and possible shielding • Improvment of collimators locations • Validation of new IR design Guy Wormser, Super B-Factory Workshop, Jan 04

  37. Evidence for neutron radiation? • Diode leakage current in EMC read-out • IFR background ? • J. Vavra developped a neutron detector very insensitive to photons that will be placed shortly along the beam pipe Guy Wormser, Super B-Factory Workshop, Jan 04

  38. Conclusions for short term issues • We have to look far ahead: Minimum 3 years • Look for worst case scenarios! • Look for end-product effects! • BABAR issues • Immediate concerns: SVT ATOM chip, IFRForward endcap • Next on-line: DCH DAQ • Longer term issues: SVT and EMC in 2008 • Changes in background issues • Beam-beam tails • injections • trapped events Guy Wormser, Super B-Factory Workshop, Jan 04

  39. Background issues for a Super B factory • Detector has to stay always on! • Detector Protection system : can we get rid of it? If not, it has to stand 100 MRad • Avoid all detector susceptible to instantaneous damage • Once proper rad hard technology has been chosen, occupancy will become the next major issue : ultra fast and hyper-segmented Guy Wormser, Super B-Factory Workshop, Jan 04

  40. Guy Wormser, Super B-Factory Workshop, Jan 04

  41. BABAR scorecard today x(trickle) X: visible effect with non-zero impact - : visible effect with no impact ? : yet unknown fixed: det upgrade to fix a significant issue Guy Wormser, Super B-Factory Workshop, Jan 04

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