IceTop Low Level Verification
IceTop data for the period of Jun 3 - Jun19 2006 have been
The runs used for the plots are
and analyzed using the latest i3 files.
The following verification plots are produced by selecting events with
IceTop Simple Majority Trigger.
DOM HV and Gains
DOM HV/Gains (for Jun3-Jun15 data)
-- verified to be the same as in
March 15 domcal6.2.4 calibration.
DOM HV/Gains (for Jun15-Jun19 data)
-- verified to be the same
as in June 15 domcal6.2.4 calibration.
-- also shown in table the gain change with
respect to March 15 calibration
1- Most gains are way off from
their nominal setting.
be 5E6, LG should be 5E4.
DAQ to do: adjust HVs to keep the gain at
2- Some DOMs show more than
20% gain change between March and June calibrations.
DAQ to do: run domcal more often
Although set to 10 PE in DAQ, the effective HG DOM thresholds are
around 30 PE.
LG DOM thresholds were supposed to be set to 1000 PE, but they are
around 4000 PE.
Why is this?
DAQ to do: lower the LG thresholds to 500 PE
The scatter plots compare the charge from low and high gain DOMs both
looking at the same event.
If the calibration is perfect the linear region between the DOMs upto
~3000 PE should
lay on the line y=x. However, LG DOM thresholds being ~4000 PE does not
allow us to see the linear
The plots show the charge spectrum of each IceTop DOM.
The black histogram is the full spectrum. The red curve shows the
contribution to the spectrum
waveforms from ATWD channel 0, the green is from ATWD channel 1, and
the blue is from channel 2.
Note the dips around the channel cross over !
This is due to the baseline correction method used. The effect of the
method is shown here.
charge comparison of the ATWD channels clearly shows the problem.
Note the 60PE offset between
channels 0 & 1, ~300PE offset between channels 1 &2.
So far the best method we found is to shift the baseline by the average
of bins 87-126.
In this case the charge spectrum is continuous, and the offsets
between the ATWD channels
is reduced to ~few PE.
However, some DOMs have double lines.
This is not due to the bipolar behaviour
of the baseline, because we adjust for it.
This must be due to calibration of the different
ATWD chips. We are investigating this.