Abstract
The SiPM-on-tile technology, consisting of plastic scintillator tiles with typical sizes of a few cm2 mounted on top of SiPMs, has been developed within the CALICE collaboration to enable automatized mass production of active elements for scintillator-based highly granular calorimeters. We present a study of the impact of misalignment of the scintillator tile with respect to the photon sensor on the response uniformity and on the absolute light yield for square, hexagonal and rhomboidal scintillator tiles of different sizes. A misalignment results in the formation of a dipole asymmetry of the spatial distribution of the light yield, with a magnitude that scales linearly with the size of the displacement, while the average light yield over the full active area of the tile is not affected. These results provide guidance for the definition of tolerances for the production and assembly of large calorimeter systems, showing that an alignment precision of approximately 500 μm or better allows to limit the impact to acceptable levels.
Highlights
For scintillator tiles with a size of around 9 cm2, as considered for hadron calorimeters at future linear electron-positron colliders, the typical dipole asymmetry introduced by a displacement of the tile with respect to the photon sensor is around 0.1 per 1 mm of displacement
This means that for such a displacement, the average signal amplitude of one half of the tile is 10% higher than that of the other half
Considering that approximately 80% of the active area of typical SiPM-on-tile designs show a response within 5% of the mean [6], limiting the displacement-induced asymmetry to below 0.05 would exclude significant light yield distortions beyond those intrinsic in the scintillator tile design
Summary
To explore the impact of a misalignment of the coupling dimple with respect to the photon sensor, the response uniformity over the active area of different scintillator tiles for varying displacements has been studied. At this point, this is purely based on laboratory measurements. Simulation studies, which have been successfully used to model response non-uniformities depending on scintillator shape [6], have not been performed in the context of this work. The response is measured using a two-dimensional scanning setup with a radioactive source, as described in the following
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