Roman Greim

A high-resolution scintillating fiber tracker with silicon photomultiplier array readout

We present prototype modules for a tracking detector consisting of multiple layers of 0.25 mm diameter scintillating fibers that are read out by linear arrays of silicon photomultipliers. The module production process is described and measurements of the key properties for both the fibers and the readout devices are shown. Five modules have been subjected to a 12 GeV/c proton/pion testbeam at CERN. A spatial resolution of 50 mu m and light yields exceeding 20 detected photons per minimum ionizing particle have been achieved, at a tracking efficiency of more than 98.5%. Possible techniques for further improvement of the spatial resolution are discussed

Silicon photomultiplier arrays – a novel photon detector for a high resolution tracker produced at FBK-irst, Italy.

A silicon photomultiplier (SiPM) array has been developed at FBK-irst having 32 channels and a dimension of 8.0 x 1.1 mm^2. Each 250 um wide channel is subdivided into 5 x 22 rectangularly arranged pixels. These sensors are developed to read out a modular high resolution scintillating fiber tracker. Key properties like breakdown voltage, gain and photon detection efficiency (PDE) are found to be homogeneous over all 32 channels of an SiPM array. This could make scintillating fiber trackers with SiPM array readout a promising alternative to available tracker technologies, if noise properties and the PDE are improved.

Indirect dark matter search with the balloon-borne PEBS detector (15'+5')

A precision measurement of the cosmic-ray positron spectrum may help to solve the puzzle of the nature of dark matter. Pairwise annihilation of neutralinos, predicted by some supersymmetric extensions to the standard model of particle physics, may leave a distinct feature in the cosmicray positron spectrum. As the available data are limited both in terms of statistics and energy range, we are developing a balloon-borne detector (PEBS) with a large acceptance of 4000 cm 2 sr. A superconducting magnet creating a eld of 0:8 T and a tracking device consisting of scintillating bers of 250 μm diameter with silicon photomultiplier readout will allow rigidity and charge determination to energies above 100 GeV. The dominant proton background is suppressed by the combination of an electromagnetic calorimeter and a transition radiation detector consisting of eece layers interspersed with straw-tube proportional counters. The calorimeter uses a sandwich of tungsten and scintillating bers that are again read out by silicon photomultipliers. The design study, based on a detailed Geant4 simulation and testbeam measurements, will be presented along with an interpretation of the currently available positron data in the context of the mSUGRA model. The constraints that future precise measurements could put on this model will be discussed.

A Scintillating Fiber Tracker With SiPM Readout

We present a prototype for the first tracking detector consisting of 250 mu m thin scintillating fibers and silicon photomultiplier (SiPM) arrays. The detector has a modular design, each module consists of a mechanical support structure of 10 mm Rohacell foam between two 100 mu m thin carbon fiber skins. Five layers of scintillating fibers are glued to both top and bottom of the support structure. SiPM arrays with a channel pitch of 250 mu m are placed in front of the fibers.

First LHC transverse beam size measurements with the beam gas vertex detector

The Beam Gas Vertex detector (BGV) is an innovative beam profile monitor based on the reconstruction of beam-gas interaction vertices which is being developed as part of the High Luminosity LHC project. Tracks are identified using several planes of scintillating fibres, located outside the beam vacuum chamber and perpendicular to the beam axis. The gas pressure in the interaction volume is adjusted such as to provide an adequate trigger rate, without disturbing the beam. A BGV demonstrator monitoring one of the two LHC beams was fully installed and commissioned in 2016. First data and beam size measurements show that the complete detector and data acquisition system is operating as expected. The BGV operating parameters are now being optimised and the reconstruction algorithms developed to produce accurate and fast reconstruction on a CPU farm in order to provide real time beam profile measurements to the LHC operators.