An electron/gamma-detector consists of a stainless steel container cone
filled to a heigth of 4.6cm with liquid scintillator.
An ionizing particle that passes the scintillator creates light, which is
detected by a photomultiplier (PM) via a light guide in the center above
the steel cone. Additionally to the PM anode also a dynode is read out to
achive the required dynamic range from 1 to 2000 minimal ionizing particles.
To prevent the dye of the scintillator from contamination by oxygen the detector is filled with argon. A plastic bag is connected to compensate for pressure differences.
Because of the cylindrical geometry the dectector response is very homogeneous over the whole area with a very good time resolution (<0.8ns). With the installed light fiber it is possible to calibrate systematic time delays between the single detectors. All this is necessary to achive a good angular resolution of better than 0.5 degrees for the reconstructed shower direction (0.1deg for the largest showers).
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