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Updated results on LXetiming

Updated results on LXetiming. D. Nicolò VRVS Meeting, 9 Feb 2004. Data analysis and sample. PRELIMINARY TASK : JUST T L -T R (  intrinsic resolution) Runs 6854 6857 (29 Nov. 2003) Live time  2h ,  25000 g collected (E>35 MeV in phase with S1&RF)

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Updated results on LXetiming

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  1. Updated results on LXetiming D. Nicolò VRVS Meeting, 9 Feb 2004 Updated results ...

  2. Data analysis and sample • PRELIMINARY TASK: JUST TL-TR( intrinsic resolution) • Runs 68546857 (29 Nov. 2003) • Live time  2h,  25000gcollected (E>35 MeV in phase with S1&RF) • FSH52 almost completely open (DAC=350) • Trigger based onS1*Q(LXe)*Q(NaI) • ABSOLUTE timing resolution • Run 7045 (6 Dec. 2003) • Live time  5h,  10000gcollected (E>35 MeV in phase with S1&RF) • FSH52 partially open (DAC=125) • Trigger based on S1*Q(LXe)*Q(NaI)*TC • High PMT gain(5106) Updated results ...

  3. Beam current monitor ~20 sbeam drop Troubles in scaler decoding as the on-line program fails to clear the scaler module in about 50% of cases Updated results ...

  4. Hardware checks • Made use of all TDC channels (FTDC+CTDC+VTDC) although  50%of back PMT see< 5 pe • Cross-talks are largely suppressed at discri level (thanks to 10ns delay cables) but stillarising in VME TDC’s Updated results ...

  5. Hardware checks (2) • Camac TDC’s look free from cross-talks, but poorer quality than FastBus L3 L8 Updated results ...

  6. Hardware checks (3) CTDC distribution still larger after time-walk corrections (TAC , cables, ?)  needs to be investigated T3 T8 Updated results ...

  7. Hardware checks (4) T1 The same jitter appears on reference counters Updated results ...

  8. The algorithm • T = TDC - Tref • TDC correction for time-walk and position • TL, TR by weighted average of Ti • <T> = (TLTR)/2 i=r.m.s. of Ti cut on Qi> 5 pe Updated results ...

  9. Intrinsic resolution (6854 ->6856) • No Tref corrections • Applied cuts: • Dr < 1cm(DT40ps) • 52<S1TDC<53 ns, 70<RFTDC<76 ns • Qsum>30000 ( E>50 MeV) • only 1000 events retained •  = 86 ps Updated results ...

  10. Intrinsic resolution (7045) • Position and Tref corrections applied • Applied cuts: • Dr < 5cm • 53.4<S1TDC<54.2 ns, 70<RFTDC<76 ns • QTC1>100, QTC2>100 • 4500 events retained • Study ofsvs Npe •  = 65 ps @ 35000 pe 20000< Npe < 30000 30000< Npe < 40000 40000< Npe < 50000 50000< Npe < 60000 Updated results ...

  11. Intrinsic resolution (2) Threshold effect Fit by  = (0.550.03) • increased QE(5%->20%) should improve the resolution Updated results ...

  12. Reference counter • 2 Pb+scint counter read by TC1,TC2,TC3,TC4 • Corrections applied for time walk • <T> = (T1+T2)/2 - (T3+T4)/2 = (901) ps worse than Ryu’s claim (need to check on the Logbook) Updated results ...

  13. Absolute timing resolution Additional cut: sigma>50 = (1473) ps @ 55 MeV 20000< Npe < 30000 10000< Npe < 20000 does not improve with statistics Position reconstruction and TC corrections are dominant 30000< Npe < 40000 40000< Npe < 50000 Updated results ...

  14. Outlook • Need to investigate hardware problems (for present and future analyses) • Made use of full analysis tools to obtain the overall timing resolution • Timing reference counter • Position reconstruction (still to be improved) • DT vs E • Increase the statistics (check on the logbook) Updated results ...

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