ZDC Status

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• ZDC Status
• A.Mestvirishvili
• Iowa

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• Quite while we had some problems with ZDC, QIE
  saturations, Reflections, Noise etc. To improve
  the situation several different steps were taken.
  
• Since for the time being we can shoot laser light
  only in one arm of ZDC (ZDC-) another arm was
  completely disconnected to avoid any possible
  ground loops. Two ZDCs have same HV grounding.
• For now we are working only with ZDC-. Channel 4
  in HAD part is discconnected
• Laserscope studies reviled a problem in a
  splitter box.

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Red arrow - signal. Green arrow -Positive spike
Splitter Box
Reduced intensity
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Signal shape without splitter
Modification splitters were removed And
signals were fed directly to QIE
No reflections scale 1us
Perfect signal scale 10ns/division
Cable directly to scope
Signal is wide width at base line is 20ns And
tail extends further, due to the very long
cables used 204m. This is perfectly Reflected
in data.
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Signal shape from data
After all this exercises and simple modifications
we started timing of ZDC- with laser Yesterday
and today we were using HF partition for timing
(ZDC is in HF partition)
EM1
EM2
Signals from all connected channels Is seen. It
is wide expected. Had1 is unusually wide Due to
the very high gain PMT. Reducing the Light bring
right hand side tail down. Settings for L1ADelay
and Pipeline length for ZDC- for now are
L1ADelay199 and Pipeline Length80
EM3
EM4
EM5
HAD1
HAD2
HAD3
HAD4 is disconnected.
Raw ADC counts vs TS, 500 Events, normalized to
one event
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Signal spectra and timing(rough calculations)
HAD1 channel with high tail
Pedestal subtracted signal distribution Peds
av. Of first two time slice Signal three TS,
maximum, one before And one after
Timing
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Pedestal run
We do not have a special configuration for ZDC
pedestals A Laser configuration file was
used Laser was pointing somewhere else and light
was attenuated as much as possible (both
attenuator wheels at position 12) 10000K Events
were taken in this mode
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Pedestals
EM1
EM2
EM3
EM4
EM5
HAD1
HAD2
HAD4
To broad and strange pedestal distributions
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Pedestals Event by event
Four event in this plot
In some cases pedestals within the event drops to
zero Event 16 , TS 1-10
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Conclusion and TODO

• Splitter was causing reflections, after removing
  the splitters good signal.
• ZDC- is timed in with lather. For now
  L1ADelay199 and PL80 (L1ADelay is likely to
  change)
• Same is needed to be done for ZDC
• ZDC and ZDC- has to be equalized, now one of the
  ZDC arm 141ns shorter in terms of lather light
  propagation to PMT.
• Strange behavior of the pedestals noise? (most
  probably) needs to be understood