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Timing Counter Status

Timing Counter Status. Timing Counter 2008 configuration Monitoring and Calibrations Timing resolution (TC and MEG). G.Cavoto INFN Roma Feb 18 th 2009. Timing Counter (TC). Two sectors, D own S tream and U p S tream, each with 15 scintillator bars readout by PMTs (TICP)

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Timing Counter Status

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  1. Timing Counter Status • Timing Counter 2008 configuration • Monitoring and Calibrations • Timing resolution (TC and MEG) G.Cavoto INFN Roma Feb 18th 2009 G. Cavoto

  2. Timing Counter (TC) Two sectors, DownStream and UpStream, each with • 15 scintillator bars readout by PMTs (TICP) • Trigger • Measure time, and z • 256 Scint. Fibers readout by APDs (TICZ) • (Meant for) geometrical trigger selection • Measure z G. Cavoto

  3. Hardware upgrades • Reduced APD noise • Light tight Tedlar foil added New EVAL bag for N2 Very tight! He concentration at few times atm. bkg level Some maintenance work (fix connectors,cables…) Both US and DS TC remounted in late spring G. Cavoto

  4. TICZ readout tests After installation, test with ‘pass-thru’ cosmics US TICZ • All analog channels (8 APD in one ch.) show good signals! • US TICZ digital readout working! • DS TICZ worsened by higher environmental noise • 3 (out of 8) DS TICZ readout sections failed during the 2008 run • “on-board” hardware problems: fixing deferred to 2009 fiber # G. Cavoto

  5. Laser system 256 nm 50Hz @ 532nm 50 Hz Acustic-optical pulse selectors 2 stages pulse amplifier 3m cavity 48 MHz, 1064nm Diode pumped Nd:YVO • Additional timing calibration device • Providing 532 and 266 nm light at 50 Hz • Optical fibers distribution to TC bars (and XEC) • Problems in operation: • environment temperature became too high  cavity unstable  drift in the feedback signal  electronic saturation, damages of optical components and electronics. • For 2009 run: • Proper box with actively stabilized temperature • Retuning of cavity • - New feedback electronics G. Cavoto

  6. PMT gain equalization • Select Michel positron hitting bar center(magnetic field ON) • Change HV to havesame average chargefor PMTs of the same bar Before After G. Cavoto

  7. TC measurements e+ DRS3 digitization for Double Threshold Discriminator NIM pulses t0 and t1 extracted with waveform template fit to NIM pulses. Checked with cross-correlation method (optimal filtering). PMT1 PMT0 h L amplitude of PMT signal effective velocity T : time of positron at the impact point on first hit bar (connected to the positron track from DCH) h : impact point along bar length (z direction) G. Cavoto

  8. TC calibrations Timing with DTD NIM signals G. Cavoto

  9. ‘Double’ and ‘triple’ hit events bar # On events with three adjacent hit bars (triples) minimize the differences (for all the bars) e+ TC TA 1st bar TB |z| On sample of two hit adjacentbars (‘doubles’) test time walk correction (c0 and c1) ns G. Cavoto

  10. TC time resolution Upper limit on average time resolution () in 60-90ps range Includes effect of DRS digitization (~10 ps) (estimated sending same signal to two DTD inputs) • Estimate of single bar time resolutionAssuming the two bars to have the same intrinsic time resolution G. Cavoto

  11. TC time resolution stability Runs 24xxx Runs 25xxx Runs 26xxx Runs 27xxx Runs 29xxx Runs 30xxx Runs 31xxx • Same TW calibration constants • Stable over timeno need of different sets of constants G. Cavoto

  12. Inter-PMT offsets • Dedicated cosmics runs taken in different down-time periods • Select event with 1 or 2 hit bar • Assume symmetric distribution along the bars Most of the bars have this flat distribution t1 - t0 [ns] Data taken in different periods very consistent (TICP very stable!!!) G. Cavoto

  13. MEG physics runs TC hitmap After Before Distribution nicely “justifies” Need veff to have the correct z scale US DS t1-t0 [ns] t1-t0 [ns] G. Cavoto

  14. Effective velocity with TICZ Pass-thru cosmics, 2 hit fibers (clusters) expected Single-cluster inefficiency: 27% due to cosmics geometrical inefficiency + dead/hot fibers (5%) Using Bar16 veff (cm/ns) Syst err.1.5% zbar-zfiber (cm) G. Cavoto

  15. Inter-bar offset extraction Boron events 4.4MeV (XEC) and 11.7MeV(TC) • Gaussian fits. • Cosmic background evaluated in runs with no-beam and same trigger requirements (TC & XEC) • Syst error on calibration constants at 50ps level Bar14 -signal -bkg (rescaled) Bar17 -signal -bkg (rescaled) T[ns] T[ns] G. Cavoto

  16. Inter-bar offsets monitoring Bar15: change in DRS board T mean [ns] Sep 08/10 Weekly monitoring (periodic DB updates) 13/10 time 20/10 25/10 10/11 24/11 01/12 relative to bar 17 bar# • No clear trend vs time • Relative offsets stable G. Cavoto

  17. DCH-TC match hitmap Extrapolate tracks from DCH to TC bars Given a track and a TC bar hit matching efficiency is 91% Some data/MC discrepancy [cm] G. Cavoto

  18. MEG absolute time offset Dalitz 0 events • Same topology as signal ! • Gamma/positron energy range (can be chosen) same as for signal • Worse resolution due to LH2 target Comparison with signal is not exact Bar17 μ = 26.06±0.01ns  = 267±10ps Centre of signal window Control sample (flight length correction) MC validation ns G. Cavoto

  19. Timing systematics check Dalitz after calibration with Boron Dalitz before calibration T (e) [ns] T (e)-T (e)(bar17) [ns] Boron (E=4.4MeV) Dalitz (E>45MeV) Relative to bar 17 bar# bar# Residual time walk effecton XEC timing Residual inter-bar differences (different target for 0 Dalitz) G. Cavoto

  20. Summary • TICP very stable over the 2008 run. • TICZ: 13 out of 16 sectors working. • Calibration strategy developed and successfully applied to data. • Data monitored during data-taking. • Some fine-tuning still needed • Residual bar differences • Detailed data-MC comparison G. Cavoto

  21. Outlook for 2009 • Detector activity • New APD electronics • Shorter shaping time to fit trigger timing • Currently prototyping new el. boards • LASER • Upgrade of TC slow control • On track for a 2009 data-taking period • Data analysis • Calibrated TC data and TC simulation available for MEG analysis • MEG timing measurements well underway G. Cavoto

  22. Back up G. Cavoto

  23. New APD electronics To insert APD into trigger • Requirements: • fast signal ( 3-5 times faster)  15ns achievable. • better EMI immunity • Implement redundant schemes for the command transmission (I2C) • Improve over all settings capability ( on board test /calibration signal,…) • Bread-boarding is started, final design of the prototype board will be sent for the production by Dec 08. Test pulse response Move Amplifier to the APD board and/or differential input G. Cavoto

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