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Machine-Detector Interface (MDI) report

Machine-Detector Interface (MDI) report. Presented by M. Weaver, SLAC. Operational issues radiation aborts radiation-dose and background monitoring Background sources and extrapolation characterization experiments long-term projections & vulnerabilities simulations

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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 • radiation-dose and background monitoring • Background sources and extrapolation • characterization experiments • long-term projections & vulnerabilities • simulations • IP characterization measurements

  2. B. Petersen Run-5 radiation-abort history <stable-beam trips> ~ 1.3/day (Run5a), 4.3/day (Run5b)

  3. BW Diamond Run-5 radiation-dose rates 60 160 BE Diamond Dose rate (mrad/s) Dose rate (mrad/s) 0 0 LER arc 1 vent HER Q5 NEG outgassing VGCC 2187 VGH 7039 Log10 pressure (T) Log10 pressure (T)

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

  5. LER injection-quality monitor HER injection-quality monitor 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.

  6. LER injection-quality monitor HER injection-quality monitor Injection- & trickle- background history Monitor using triggers gated around the passing of the injected bunch (1 ms x 15 ms) Injection contaminates the BaBar physics data sample if backgrounds endure too long

  7. Stored-beam background history IDCH, msrd/pred DCH current normalized to Jan 04 background data Beam currents Limited by BaBar deadtime HER Q5 NEG outgassing L1 Deadtime (%)

  8. Background sources in PEP-II • Synchrotron radiation (this bkg negligible in PEP-II, but not in KEKB) • 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)

  9. DCH Background Characterization experiments were performed in Jan’04. Isolated beam-gas, beam-beam, and luminosity driven backgrounds. Allows prediction of future background impact on detector performance. Predictions are still valid in the absence of abnormal vacuum activity. Should repeat characterization when changes in PEP-II warrant. Still need to update predictions with new PEP-II performance projections, but implications are similar. Tracking efficiency drops by roughly 1% per 3% occupancy LER contribution very small

  10. Backward: East Top West Bottom Background strongly - dependent By 2007 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 SVT Integrated dose will be more than 1 Mrad/year by 2007 Background now is ~75% HEB [LEB negligible (!)] In 2007, it will be 50% HER, 50% L • It has been realized that in the SVT (but not in other subdetectors), a large fraction of the “Luminosity”background is most likely due to a HER-LER beam-gas X-term (but: similar extrap’ltn).

  11. Scrubbing the new HER Q5 chamber 3 Run 5a 0 L1Rate / Prediction 3 Run 5b Greater than x2 0 Time The trigger rate was effected considerably more than the drift chamber occupancy or current

  12. DCH Feature Extraction Bottleneck Deadtime (%) Front-end Readout (4 buffers) Trigger Rate (Hz) Deadtime problem was foreseen in DAQ projections “Phase I” drift chamber electronics upgrade Installed for Run5a Addressed the “Front-end Readout” contribution to deadtime (factor x2 improvement) “Phase II” upgrade Installed for Run5b but not yet activated Addresses both components sufficiently for the lifetime of BaBar (factor x2, x3 improvement)

  13. Projected DAQ Requirements/Performance Fiber Transfer upgraded L1 Rate (Hz) Repartition or run @60MHz Processing Time upgraded VME Transfer Feature Extraction (Easy) code optimization Will re-split this crate Overestimated ! Processing Time Processing Time

  14. Given that future backgrounds have serious implications for detector performance, can anything be done to mitigate them? • Beam-gas backgrounds : manage residual gas pressure • Luminosity backgrounds : learn how to shield • Beam-beam backgrounds : learn how to collimate • Need to turn to simulation to improve our understanding and test mitigation strategies.

  15. Monitoring of single-beam backgrounds Take single beam background data opportunisticly to monitor vacuum Jul’05 Jul’05 Jan’04 Model HER current (A) LER current (A)

  16. GEANT4 Simulation of Luminosity backgrounds Simulation of luminosity background in the EMC C. Cohalan

  17. Neutrons J. Va’vra A high rate of neutrons is generated from radiative Bhabha interactions. These neutrons are believed responsible for DCH electronics radiation upsets at a rate of 2/hour. A small fraction of these alter the electronics behavior, and data acquisition must be paused to re-configure the electronics.

  18. Beam-beam background collimation Turtle simulation of LER scattered particles striking near IP Collimator added to Mitigate LER beam-beam background +25.2 m from IP LER Collimators removed to prevent HOM heating X [mm] S.Majewksi, W.Kozanecki

  19. IP Characterization • Use BaBar’s tracking resolution and prime venue for measuring important parameters at the IP • Three analyses each measuring ey, b*y (see J.Thompson’s talk) • 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

  20. 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 } every ~hour • Boost Trajectory • mean { x’, y’ } every 10 minutes • spread { x’HER, y’HER } every 30 minutes }

  21. Compare boost trajectory and luminous region tilt -20.6 x’boost – dx/dz lumi ≈ full crossing angle (10’ online measurement) xz angle (mrad) -22.4 0 Moving one beam in a controlled experiment yields each beam’s x-size (1 day) sL = 68mm sL=80mm, sH=140mm xz crossing angle (mrad) -1

  22. Studies on Luminosity Transient mm Events DCH time resolution allows event association to RF bucket Studied many IP parameters along bunch train z-centroid, size x,y-centroids, x-size x’,y’ means and spread 20% mini-train z-centroid x-size mm 66mm 63mm mini-train full-train

  23. Measuring Coupling at the IP with BaBar s2xs2xx’s2xys2xy’ s2x’s2x’ys2x’y’ s2ys2yy’ s2y’ “coupling” Single Beam Covariance Matrix S = Effect of Coupling on Luminosity Reduced overlap Beam size evolution Tilt of the Luminous Region (s2xy ) Weighted by beam size Tilt of the Angular Spread (s2x’y’ ) Weighted by beam energy waist offset LER HER

  24. Tilt Angle (mrad)  (rad) Measuring x’y’: “Tilt Angle” “eigenmode 1” Boost angular spread “eigenmode 2”

  25. Effort to Measure Off-Diagonal Elements via Boost – Position Correlations Z Dependence Similarly for y, but resolution needs to be handled better dx’boost / dx dx’boost / dy Expect large correlated detector errors Expect slope from physics Expect no correlated detector errors s2XX’ / s2X (mrad-mm-1) s2YX’ / s2Y (mrad-mm-1) b*x (coupling) dy’boost / dy dy’boost / dx Very strong z-dependence s2YY’ / s2Y (mrad-mm-1) s2XY’ / s2X (mrad-mm-1) (b*y) coupling

  26. Summary (I) • Stable-beam (genuine) radiation aborts are ~ 1/day (Run5a) Vacuum induced instabilities(?) add to make ~ 4/day (Run5b) • Injection backgrounds are monitored and under control • Stored-beam bgds (dose rate, data quality, dead time) • OK on average – problematic episodes of vacuum activity: “vacuum spikes” and HER thermal outgassing. • Background characterization experiments • Valuable in identifying the origin, magnitude & impact of single- & two-beam backgrounds – be opportunistic • Maintain a measure on the projected backgrounds – impacts detector remediation/upgrades with long lead times • No new dedicated experiments performed – OK as long as there are no surprises (e.g. beam-beam backgrounds)

  27. Summary (II) • Main vulnerabilities are • beam-gas backgrounds from HOM-related thermal outgassing as I+,- • high dead time associated with data volume & trigger rates (SVT readout then EMC feature extraction – ultimately may tighten trigger) • high occupancy and radiation ageing in the mid-plane of the SVT, • possibly leading to a local loss of tracking coverage. • a high flux of ~ 1 MeV neutrons in the DCH (radiation upsets, wire aging from large pulses, possibly also contributions to occupancy) • Background simulations • Slow progress • manpower limited – losing our “workhorse” • BaBar-based IP characterization • Increasing amount of measurements reported online • Significant amount of offline analysis to understand important parameters

  28. MDI abstracts submitted to EPAC06 • Monitoring of Interaction-Point Parameters using the Three-Dimensional Luminosity Distribution Measured at PEP-II • B.Viaud, W. Kozanecki, C. O’Grady • Characterization of the PEP-II Colliding Beam Phase Space by the Boost Method • M.Weaver, W.Kozanecki • Combined Phase Space Characterization at the PEP-II IP using Single-Beam and Luminous-Region Measurements • A.Bevan, Y.Cai(?), A.Fisher(?), W.Kozanecki, C.O’Grady, J.Thompson, B.Viaud, M.Weaver

  29. Spare Slides

  30. Crossing angle history

  31. Boost Angular Spread history (sampled) sx’ (mrad) Run1 Run2 Run3 Run4 Run5 sy’ (mrad)

  32. x’ (mrad) y’ (mrad) y (cm) x (cm) Example: -1.5 < Z(cm) < -0.9 Non-zero offset Large correlation Problematic non-linearity (“S-shape”) Large correlation Small but significant correlation (Resolution dominated)

  33. Toy+ FullMC FullMC no HG X-X’ Correlation Simulation Studies Toy bbi low curr s2XX’ / s2X (mrad/mm) Z (cm) bbi high curr Using b* from single beam distributions - - Analytic prediction = z fH - fL b*2H+z2b*2L+z2

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