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

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

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

Guy Wormser, Super B-Factory Workshop, Jan 04 4 Predictability score zPredictables sources ySynchrotron yBeam gas xBremstralhung xCompton yTouschek zIn principle predictable source yRadiatvie Bhabbas zUnreliably predictable sources yBeam-beam yElectron cloud effects yInjection doses zUnpredictable sources yRadiation 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 DCH background history M. Kelsey

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 zExample of DIRC TDC y In 1999, we predicted that the single rate PMT in the DIRC would in exceed the 200 kHz limit yA lot of effort to improve the shiedling yLaunch design of a new TDC, implemented in summer 2002 with a 2 MHz capability. yThe 200 kHz limit was indeed reached in fall 2002 zNext on line: DCH read out!

Guy Wormser, Super B-Factory Workshop, Jan DIRC main source of background: Radiative Bhabhas striking Q4 magnet inboard flange z Source discovered empirically with a Geiger counter. z Shielding erected step-by-step slowly building empirically a proof that things are improving. z A final shield erected in 2001, and the whole job completed in z 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 IFR issues zIFR 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 IFR issues

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

Guy Wormser, Super B-Factory Workshop, Jan SVT Background from HER (BW:MID) Moves toward half-integer HER sensitive SVT module (Does not have threshold shift problem): 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! For occupancies in all SVT modules, see:

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

Guy Wormser, Super B-Factory Workshop, Jan Single beam and lumi sensitivity HERHER **2 LERLER* *2 Lumi SVT( mid) XY0 DCH DRC EMC

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

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

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

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

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

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

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

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

Guy Wormser, Super B-Factory Workshop, Jan Example in

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

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

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

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

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

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

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

Guy Wormser, Super B-Factory Workshop, Jan Revided simulation efforts zLocations of the sources of Lumi terms and possible shielding zImprovment of collimators locations zValidation of new IR design

Guy Wormser, Super B-Factory Workshop, Jan Evidence for neutron radiation? zDiode leakage current in EMC read-out zIFR background ? zJ. 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 Conclusions for short term issues zWe have to look far ahead: Minimum 3 years zLook for worst case scenarios! zLook for end-product effects! zBABAR issues yImmediate concerns: SVT ATOM chip, IFRForward endcap yNext on-line: DCH DAQ yLonger term issues: SVT and EMC in 2008 zChanges in background issues yBeam-beam tails yinjections ytrapped events

Guy Wormser, Super B-Factory Workshop, Jan Background issues for a Super B factory zDetector has to stay always on! z Detector Protection system : can we get rid of it? If not, it has to stand 100 MRad yAvoid all detector susceptible to instantaneous damage zOnce 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 BABAR scorecard today X: visible effect with non-zero impact - : visible effect with no impact ? : yet unknown fixed: det upgrade to fix a significant issue x(trickle)