Abstract
The progresses in the micropulling-down technique allow heavy scintillating crystals to be grown directly into a fibre geometry of variable shape, length and diameter. Examples of materials that can be grown with this technique are Lutetium Aluminum Garnets (LuAG, Lu3Al5O12) and Yttrium Aluminum Garnets (YAG, Y3Al5O12). Thanks to the flexibility of this approach, combined with the high density and good radiation hardness of the materials, such a technology represents a powerful tool for the development of future calorimeters. As an important proof of concept of the application of crystal fibres in future experiments, a small calorimeter prototype was built and tested on beam. A grooved brass absorber (dimensions 26cm×7cm×16cm) was instrumented with 64 LuAG fibres, 56 of which were doped with Cerium, while the remaining 8 were undoped. Each fibre was readout individually using 8 eightfold Silicon Photomultiplier arrays, thus providing a highly granular description of the shower development inside the module as well as good tracking capabilities. The module was tested at the Fermilab Test Beam Facility using electrons and pions in the 2–16 GeV energy range. The module performance as well as fibre characterization results from this beam test are presented.
Highlights
This content has been downloaded from IOPscience
We reported earlier [6] about a beam test conducted at CERN in 2012, where 9 LuAG fibres of good optical quality were inserted in a small brass absorber and exposed to high energy electrons at the H2 beam line of the CERN SPS North Area
The breakdown voltage and the recovery time were measured in laboratory to be 25.4 V and 30 ns respectively. The choice of this particular Silicon PhotoMultiplier (SiPM) model was mainly dictated by the photon detection efficiency (PDE), which is about 20% at the LuAG:Ce emission peak (520 nm) and is high in the UV region (∼ 18% at 350 nm), which enhances the detection of Cherenkov photons produced in undoped LuAG fibres
Summary
The beam we used for this test was provided by the Fermilab Test Beam Facility (FTBF). Our magnet configuration allowed secondary particles to be produced in the 1–32 GeV energy range, with a momentum resolution of ∼ 2.5% or better. A sketch of the experimental area hosting our setup can be seen in figure 2: a scintillation counter was located at the entrance of the hall, providing the trigger information in coincidence with the spill signals; a couple of multi-wire proportional chambers (labelled WC1 and WC2 hereafter) were situated few tens of centimeters upstream of our setup and allowed the beam position in the x − y plane to be reconstructed with ∼ 1 mm spatial resolution; our calorimetric module was centered on the beam by means of a remotely-controlled moving table (in the x and y directions).
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