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Machine-Detector Interface (MDI) report

Machine-Detector Interface (MDI) report. Presented by M. Weaver, SLAC. Operational issues radiation aborts background monitoring Background extrapolations model comparisons to performance simulations vulnerabilities IP characterization measurements. Jan 2007. Mar 2007. May 2007.

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Machine-Detector Interface (MDI) report

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  1. Machine-Detector Interface (MDI) report Presented by M. Weaver, SLAC • Operational issues • radiation aborts • background monitoring • Background extrapolations • model comparisons to performance • simulations • vulnerabilities • IP characterization measurements

  2. Jan 2007 Mar 2007 May 2007 Jul 2007 Sep 2007 B. Petersen S. Curry Run-6 radiation-abort history <stable-beam trips> ~ 2.8/day

  3. Jan 2007 Jan 2007 Mar 2007 Mar 2007 May 2007 May 2007 Jul 2007 Jul 2007 Sep 2007 Sep 2007 Abort-by-dose location Forward West Forward East HER vacuum events Backward West Backward East

  4. Background Monitoring Summary • SVTRAD diodes + diamonds dose rates, dose / injection • DCH high voltage current • DRC PMTs scaler rates • IFR high voltage current • Fast Control & Timing deadtime, L1 rates, time wrt injection • Level 3 Trigger subdetector occupancies • Neutron counters scaler rates • CsI IP detectors (logarithmic response) • All update in small intervals (1-5 seconds)

  5. Run-6 radiation-dose rates BE Diamond BW Diamond Dose rate (mrad/s) Incoming LER Vacuum Incoming HER Vacuum Pressure (nT)

  6. 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. LER injection-quality monitor HER injection-quality monitor Average Dose/Injection (mrad) Average Dose/Injection (mrad)

  7. DIRC PMT Scaler Rate DIRC reconstruction has been shown to be robust up to 1MHz hit rate.

  8. Tuned noise thresholds and tightened time windows Detector Occupancies (%) SVT Layer 1 West SVT Layer 1 East EMC Total DCH Total

  9. Background sources in PEP-II • Beam-gas (bremsstrahlung + Coulomb) • HEB only: BHbg ~ IH * (pH0 + PHDyn * IH) Note: p0 = f(T) ! • LEB only: BLbg ~ IL * (pL0 + PLDyn * IL) Note: p0 = f(T) ! • beam-gas x- term: BLHbg ~ cLH * IL * IH (LEB+HEB, out of collision) (?) • Luminosity (radiative-Bhabha debris) – major concern as L  • BP ~ dP * L (strictly linear with L) • Beam-beam tails • from LER tails: BL, bb ~ IL * fL(xL,H+/-) • from HER tails: BH, bb ~ IH * fH(xL,H+/-) • Trickle background: BLi ,BHi(injected-beam quality/orbit + beam-beam) • Touschek: BLT(signature somewhat similar to bremstrahlung; so far small) Still using characterization of Jan’04

  10. Projected DAQ Requirements/Performance 7.0kHz “ceiling” 5.8kHz average L1 Rate (Hz) Time upgraded Feature Extraction Fiber Transfer upgraded Threshold tuning and window tightening upgraded Processing Time Processing Time

  11. Backward: East Top West Bottom Background strongly - dependent Predict 80% chip occupancy right in MID-plane In layer 1, 10% will be above 20% occupancy NOW 2004 2005 2006 2007 Forward: East Top West Bottom Projected Detector Occupancies SVT Integrated dose will be more than 1 Mrad/year Background will be 50% HER, 50% L

  12. Background model comparisons(measured/model) Bwd West Dose Rate Bwd East Dose Rate Ratio HER vacuum performance still better than predictions from Jan’04 characterization. Lots of vacuum work during pre-Run6 downtime resulted in a long time to scrub.

  13. Background model comparisons(measured/model) DCH Background L1 Trigger Rate Trigger rate somewhat larger than characterization. Results in higher deadtime. Run6 backgrounds still consistent with characterization.

  14. Background model comparisons(measured/model) DRC Background Large fluctuations but tolerable in this subdetector.

  15. 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. Secondary Interactions + Detector Response (GEANT) Accelerator Design (MAD) Primary Interactions (Turtle)

  16. Detector Vulnerabilities Extrapolation (5.8kHz) • Readout Deadtime • Inefficiencies, backgrounds (combinatorics) • Damage x2 Background (7kHz) Total SVT A tightened “emergency” trigger configuration is ready, just in case… DCH EMT BaBar experts are estimating worst tolerable conditions

  17. IP Characterization • Use BaBar’s tracking resolution and prime venue for measuring important parameters at the IP • Three analyses each measuring ey, b*y • dLumi / dz vertexing e+e- and m+m- events • syLumi(z) m+m- events • sy’Lumi(z) m+m- events e- beam (resolution) Production vertices (x,y,z ~ 30mm) Boost trajectories (q ~ 0.6 mrad) e+ beam

  18. 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 { Sz, b*y, zw, zc} every ~hour • Boost Trajectory • mean { x’, y’ } every 10 minutes • spread { x’HER, y’HER } every 30 minutes }

  19. s s z z , , H L Bunch Length Extraction from dL/dz Fits DVRF by* = 13mm Sz (mm) DSz2 = 10.3 mm2± 0.4 mm2 10.9 mm 10.4 mm 10.8 mm ± 0.2 mm ± 0.2 mm BaBar Run

  20. IP Beta Function Measurements dL /dz syL PEP phase advance b2 sy’B

  21. 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.

  22. 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

  23. Spare Slides

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