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HCAL stability Yu. Guz, IHEP, Protvino 25/06/2008

HCAL stability Yu. Guz, IHEP, Protvino 25/06/2008. Several long LED runs were recently taken. Used to study the PM stability, and for development of the LED calibration algorithm

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HCAL stability Yu. Guz, IHEP, Protvino 25/06/2008

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  1. HCAL stability Yu. Guz, IHEP, Protvino 25/06/2008

  2. Several long LED runs were recently taken. Used to study the PM stability, and for development of the LED calibration algorithm The calibration farm exists (hlta08 +3 nodes); however not all software components available  still work offline on stored LED data. Exists as a Gaudi algorithm, tested within Orwell (to be easily transformed into a calibration task). Should work on ECAL and HCAL (PRS?) To be finalized in July (the CONDDB entries for LED calibration data to appear by then, see yesterday Olivier’s talk) As a byproduct, the stability information was used to identify (and try to fix) HW problems in HCAL

  3. HCAL LED data available Side C+A: 5 identical LED time scans of 13 points, 1600 ev/point, LEDs #1 used, firing rate 1/16. Used to evaluate HCAL C general status, also 2 unstable PM/CWs identified Side A: long run 150 sequences 1600 TAE/seq, interval 5 min. Used to study the stability. 3 most unstable cells identified ODIN time is not available in these runs  event # was used for plots

  4. HCAL: status side C Good news: no dead cells. Time alignment is reasonable (maybe 152 will be somewhat better than 150) 2 unstable cells found (PM replaced during last access before closing the detector) T0, all the 5 scans O_05_05: ~10% variations O_06_11: ~3% variations

  5. HCAL: status side C LEDTSB calibration problems: ch 22 and 24 Next1, run 023356 Ch 22 Ch 0: ok Ch 24

  6. HCAL: status side A Also, no dead cells. General stability: very good (variations ~1%) 3 most unstable cells: I_18_20, I_30_24, O_26_10 PM/CW replaced Bad ATI fixed

  7. HCAL: status side A T0 LED signal stability: very good (within +-0.1%) However a timing problem appeared in one of LEDs (still not understood, suspect loose contact in the firing LVDS cable) T0 Next1

  8. HCAL: status side A More observations:1st event in a sequence (right after reconfiguration of LEDTSB) has wrong timing (to be skipped) T0 Next1

  9. Conclusions The development of online LED calibration algorithm is under way. The LED data taking with DAQ is a good tool to identify hardware problems. HCAL PM stability was studied. Several HW problems found, an attempt to fix was made. The result is not yet verified  it would be nice to take LED data once more More generally – could the existing CALO DAQ and LED monitoring system be easily available during hardware interventions?

  10. PM gain measurement in situ(on behalf of Jacques and Irina)(preliminary, to launch a discussion) The HV setting calculation using average ph.el. yield (3100, 3500, 2600 for I, M, O) gives precision of ~10% rms because of spread in QE and light yield of modules. The existing HAMAMATSU data on PM gain may be not perfect: 1) they were obtained with different dynode HV distribution; 2) there may be uncertainty in HV values of CW bases; 3) the extrapolation to gains of ~103 gives additional uncertainty Hamamatsu data • We can try to re-measure gains using existing DAQ and LED system: • measure gain by photo statistics at one or more “comfortable” points where photo statistics gives dominant contribution to the width (G~100k?) • taking into account the CW noise, i.e. measuring also pedestals • controlling LED stability by PIN readout (if possible) • take into account the Fano factor (~0.85) • extrapolate to desired gain by varying HV and measuring only amplitude • we can measure sum of two BX, in order to not care about timing • for this, record TAE without pedestal subtraction, and subtract pedestals offline

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