Lav monitoring and tot
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LAV monitoring and TOT. F.Ambrosino, G. saracino. The monitoring (and calibration ) principle. Fit a linear relation between s Q 2 and Q, by varying the LED pulser intensity.

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LAV monitoring and TOT

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Lav monitoring and tot

LAV monitoring and TOT

F.Ambrosino, G. saracino


The monitoring and calibration principle

The monitoring (and calibration ) principle

  • Fit a linear relation between sQ2 and Q, by varying the LED pulser intensity.

  • This allows a precise determination of the gain and has been succesfully used to characterize and intercalibrate the blocks using the “oven”

  • Uses the CHARGE and its fluctutation (as measured by a QDC) as inputs

  • Aim of the commissioning: test for the first time this system with the ToT electronics.


Commissioning of the monitoring system

Commissioning of the monitoring system

  • Due to time constraints the full commissioning of the LAV monitoring system was not possible during October test beam.

  • We checked the LED module and pulsed all the blocks, but we did not acquire data with the full DAQ chain.

  • We decided to reproduce the full DAQ system at LNF and to test it using our LED module + the complete fiber light distribution chain


Results tot vs q

Results: ToT vs Q

  • Good correlation between ToT and charge for various LED intensities, and at different ToT thresholds

10 mV THR


Results tot vs q1

Results: ToT vs Q

  • Good correlation between ToT and charge for various LED intensities, and at different ToT thresholds

30 mV THR


Results sigma tot vs q

Results: sigma ToT vs Q

  • Apparently NO (or wrong) correlation between the sigma of the ToT and the charge…

10 mV THR


Results sigma tot vs q1

Results: sigma ToT vs Q

  • Apparently NO (or wrong) correlation between the sigma of the ToT and the charge…

30 mV THR


Results sigma tot vs q2

Results: sigma ToT vs Q

  • Not a problem of the TOT board. We checked using the scope and obtained the same result i.e. sigma ToT does not follow sigma charge.

  • The LED pulser module has been optimized for stability (temperature controlled) and light yield (need to split each light signals on 16 fibers with two level of optical couplings in between). Not for producing very fast signals.

  • Check on data from test beam if a fast source (a track) is better.


Results sigma tot vs q muon run

Results: sigma ToT vs Qmuon run

  • Some encouraging results..


Results sigma tot vs q muon run1

Results: sigma ToT vs Qmuon run

  • …but situation not clear yet


Results sigma tot vs q muon run2

Results: sigma ToT vs Qmuon run

  • …but situation not clear yet


Results tot vs q2

Results: ToT vs Q

Some slices of the ToT vs Q distribution.

Clear evidence of the refirings on the sigma, even before the “step” in the distribution.

Q= 25 pC

Q= 15 pC


Conclusions

Conclusions

The LED calibration system as it was designed (and tested using QDC…) seems incompatible with the ToT readout since ToT fluctuations does not correlate enough to charge fluctuations. Two main problems encountered:

  • An important source of fluctuations comes from the refirings caused by the divider

  • LED signal is probably not fast enough wrt PMT (LED optimized for stability and light yield)

    Solutions:

  • Change divider

  • Use fast (and lower light yield) LEDs  cannot use fibers (too many attenuations in the distribution chain)


Outlook

Outlook

We have to reconsider the possibility of equipping each block with a LED, with a (fast) external pulser as we originally proposed in one of the two possible layouts for the monitoring system.

This could have also some positive side effects on costs (no fibers, no optical flanges) but needs redesigning of the LED driver module.

A LED driver which could possibly fit our needs had already been designed and built by G. Corradi several years ago and is available at LNF. See presentation by Tommaso

Even if the sigma TOT vs Sigma Q correlation will not be recovered, as a backup option one could use the analog output of the TOT boards system and read periodically (e.g. during MD shutdowns) signals using some commercial QDCs to perform the “usual” gain measurement for each LAV station.


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