Abstract
We demonstrate how the latest generation of hybrid pixel detectors of the Timepix family can be used to reconstruct 3 dimensional particle tracks on a microscopic scale, additionally determining the stopping power along the particles’ paths. In an experiment, a Timepix3 detector with a 2 mm thick planar CdTe sensor was irradiated in a 40 GeV/c pion beam and used in a similar way to a time-projection chamber: The coordinates x and y were given by the trajectory projection (pixel pitch: 55,upmu hbox {m}), the z-coordinate was reconstructed from the charge carrier drift time measurement (time binning: 1.5625 ns). The achievable z-resolution was studied at different bias voltages. Systematic inaccuracies due to an imprecise drift time model were determined and separated from the intrinsic uncertainty given by the time resolution. It was shown that a z-resolution of 60,upmu hbox {m} could be achieved by a perfect modeling of the drift time. With the presented z-reconstruction methodology, we studied the charge collection efficiency as a function of interaction depth, which was then used to apply a charge loss correction to the per-pixel energy measurements. 3D event displays of pion, muon and electron tracks are shown.
Highlights
(while the resolution in x and y was given by the pixel pitch of 110 μm)
We show a 3D view of particle interactions seen in a 40 GeV/c pion beam at the Super-Proton-Synchrotron (SPS) at CERN1 and illustrate the signatures of different types of interactions
The presented work described the application of Timepix3 for particle tracking on a microscopic scale
Summary
Compared with the typically gas-filled TPCs, Timepix detectors profit from the advantages of the semiconductor material, such as the higher density (by two orders of magnitude) and the approximately 10 × lower energy needed to create free charge carriers, leading to the possibility to reduce the device dimension while providing precise spectroscopic information about the ionizing energy losses in the sensor. Timepix particle trackers are compact, lightweight, portable and easy to use. They can be used in places where the available space is limited, and in situations where weight or power consumption matters. Such applications include space weather analyses [7], the determination of trapped particle directions in the Van-Allen radiation belts [8,9], monitoring of secondary radiation in hadron therapy [10], the study of the antiproton annihilation [4] and electron microscopy [11]. We continue methodological development by systematically investigating the track reconstruction capabilities of a Timepix with a 2 mm thick CdTe sensor layer at different bias voltages. The drift velocity ve,h of electrons and holes, respectively, is directly proportional to the electric field: ve = −μeE,. The electric field in z-direction E(z) was found to be best described by: Timepix
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