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M. WeaverPEP-II MAC Review,15-17 Nov’07 Operational issues radiation aborts background monitoring Background extrapolations model comparisons to performance simulations vulnerabilities IP characterization measurements Machine-Detector Interface (MDI) report Presented by M. Weaver, SLAC
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M. WeaverPEP-II MAC Review,15-17 Nov’07 Run-6 radiation-abort history B. Petersen S. Curry ~ 2.8/day Jan 2007 May 2007 Sep 2007 Jul 2007 Mar 2007
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M. WeaverPEP-II MAC Review,15-17 Nov’07 Forward West Forward East Backward West Backward East Abort-by-dose location HER vacuum events Jan 2007 May 2007 Sep 2007 Jul 2007 Mar 2007 Jan 2007 May 2007 Sep 2007 Jul 2007 Mar 2007
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M. WeaverPEP-II MAC Review,15-17 Nov’07 Background Monitoring Summary SVTRAD diodes + diamondsdose rates, dose / injection DCH high voltagecurrent DRC PMTsscaler rates IFR high voltagecurrent Fast Control & Timingdeadtime, L1 rates, time wrt injection Level 3 Triggersubdetector occupancies Neutron counters scaler rates CsI IP detectors(logarithmic response) All update in small intervals (1-5 seconds)
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M. WeaverPEP-II MAC Review,15-17 Nov’07 Run-6 radiation-dose rates Dose rate (mrad/s) Pressure (nT) Incoming HER Vacuum BW Diamond BE Diamond Incoming LER Vacuum
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M. WeaverPEP-II MAC Review,15-17 Nov’07 Injection- & trickle- background history Monitor by integrating SVTRAD diode signals over 12 ms after each injection SVT electronics are sometimes “upset” by exposures greater than 50 mrad / injection. HER injection-quality monitor LER LER injection-quality monitor Average Dose/Injection (mrad)
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M. WeaverPEP-II MAC Review,15-17 Nov’07 DIRC PMT Scaler Rate DIRC reconstruction has been shown to be robust up to 1MHz hit rate.
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M. WeaverPEP-II MAC Review,15-17 Nov’07 Detector Occupancies (%) SVT Layer 1 East SVT Layer 1 West DCH Total EMC Total Tuned noise thresholds and tightened time windows
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M. WeaverPEP-II MAC Review,15-17 Nov’07 Background sources in PEP-II Beam-gas (bremsstrahlung + Coulomb) HEB only: B Hbg ~ I H * (p H 0 + P H Dyn * I H ) Note: p 0 = f(T) ! LEB only: B Lbg ~ I L * (p L 0 + P L Dyn * I L ) Note: p 0 = f(T) ! beam-gas x- term: B LHbg ~ c LH * I L * I H (LEB+HEB, out of collision) (?) Luminosity (radiative-Bhabha debris) – major concern as L B P ~ d P * L (strictly linear with L) Beam-beam tails from LER tails: B L, bb ~ I L * f L ( L,H +/- ) from HER tails: B H, bb ~ I H * f H ( L,H +/- ) Trickle background: B Li, B Hi Trickle background: B Li, B Hi (injected-beam quality/orbit + beam-beam) Touschek: B LT Touschek: B LT (signature somewhat similar to bremstrahlung; so far small) Still using characterization of Jan’04
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M. WeaverPEP-II MAC Review,15-17 Nov’07 Projected DAQ Requirements/Performance Processing Time Fiber Transfer Feature Extraction Processing Time Threshold tuning and window tightening upgraded L1 Rate (Hz) Time 7.0kHz “ceiling” 5.8kHz average upgraded
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M. WeaverPEP-II MAC Review,15-17 Nov’07 SVT Integrated dose will be more than 1 Mrad/year Backward: Forward: TopEastWestBottom TopEastWestBottom NOW 20042005 20062007 Background will be 50% HER, 50% L Background strongly - dependent Predict 80% chip occupancy right in MID-plane In layer 1, 10% will be above 20% occupancy Projected Detector Occupancies
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M. WeaverPEP-II MAC Review,15-17 Nov’07 Background model comparisons (measured/model) Bwd East Dose Rate Bwd West Dose Rate Lots of vacuum work during pre- Run6 downtime resulted in a long time to scrub. HER vacuum performance still better than predictions from Jan’04 characterization. Ratio
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M. WeaverPEP-II MAC Review,15-17 Nov’07 DCH BackgroundL1 Trigger Rate Background model comparisons (measured/model) Trigger rate somewhat larger than characterization. Results in higher deadtime. Run6 backgrounds still consistent with characterization.
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M. WeaverPEP-II MAC Review,15-17 Nov’07 DRC Background Background model comparisons (measured/model) Large fluctuations but tolerable in this subdetector.
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M. WeaverPEP-II MAC Review,15-17 Nov’07 Machine Background Simulations Long effort to simulate sources of machine backgrounds to improve understanding Added interest from future B-factory designers Difficulty integrating tools LER model was completed long ago and simulated with not- so-satisfactory results. Problems uncovered generating HER model. At long last, HER model is consistent among the tools. Ready to simulate and analyse. Analysis may learn something in time to compare against machine operation but benefit is unknown. Accelerator Design (MAD) Primary Interactions (Turtle) Secondary Interactions + Detector Response (GEANT)
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M. WeaverPEP-II MAC Review,15-17 Nov’07 Detector Vulnerabilities Readout Deadtime Inefficiencies, backgrounds (combinatorics) Damage SVT Total DCH EMT Extrapolation (5.8kHz) x2 Background (7kHz) BaBar experts are estimating worst tolerable conditions A tightened “emergency” trigger configuration is ready, just in case…
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M. WeaverPEP-II MAC Review,15-17 Nov’07 IP Characterization Use BaBar’s tracking resolution and prime venue for measuring important parameters at the IP Three analyses each measuring y, * y dLumi / dz vertexing e + e - and + - events yLumi (z) + - events y’Lumi (z) + - events (resolution) Production vertices (x,y,z ~ 30 m) Boost trajectories ( ~ 0.6 mrad) e- beam e+ beam
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M. WeaverPEP-II MAC Review,15-17 Nov’07 BaBar IP measurements reported online Luminous Region centroids { x, y, z} sizes { x, z } every 10 minutes tilts { dx/dz, dy/dz } dL/dz fit { z, * y, z w, z c } every ~hour Boost Trajectory mean { x’, y’ } every 10 minutes spread { x’ HER, y’ HER } every 30 minutes }
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M. WeaverPEP-II MAC Review,15-17 Nov’07 V RF z (mm) Bunch Length Extraction from d L /dz Fits BaBar Run z 2 = 10.3 mm 2 ± 0.4 mm 2 zH , 10.9 mm 10.4 mm 10.8 mm ± 0.2 mm zL , ± 0.2 mm y * = 13mm
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M. WeaverPEP-II MAC Review,15-17 Nov’07 d L /dz IP Beta Function Measurements yLyL y’ B PEP phase advance 2
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M. WeaverPEP-II MAC Review,15-17 Nov’07 Summary (I) Expect a painful scrubbing process at the beginning of Run7. Lots of HER arc vacuum work done to remedy source of abort-inducing vacuum events. Injection backgrounds sometimes problematic but generally under-control Stored-beam bgds (dose rate, data quality, dead time) Some differences from run5 but similar magnitude. No new thermal outgassing/vacuum activity near the detector. Background characterization No new experiments. Too late in the game to repeat, no time for hardware interventions. Latest measures of the projected backgrounds still look good. Uncertain about beam-beam backgrounds – Run5 experiment suggested not so large, Run6 experience somewhat different.
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M. WeaverPEP-II MAC Review,15-17 Nov’07 Summary (II) Simulation After a long struggle, ready to analyze HER backgrounds. BaBar-based IP characterization Incorporating effects of coupling Working on including X-ray and SL beam profile monitors
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M. WeaverPEP-II MAC Review,15-17 Nov’07 Spare Slides
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