Speaker
Description
Our group performs R&D to improve the scintillating fibre tracker technology
(SciFi tracker) in general with the goal of transferring the technology to
large-scale projects, for example, the LHCb Upgrade II SciFi
Tracker. One of the key elements are the silicon photomultiplier
(SiPM) photodetectors. In order to overcome the challenges imposed by radiation
and low material budget, we are constantly evaluating and improving the
photodetectors. We found that the enhancement of the SiPM with pixel-level
microlenses significantly improves the effective photon-detection efficiency as
well as the single-photon time resolution. The external crosstalk is aligned
with the expectations from the geometry of the optical system.
The choice of the ideal SiPM pixel size for the SciFi Tracker is a compromise
between the high geometrical fill factor (GFF) and the resulting high photon
detection efficiency (PDE) for large pixels and the manifold disadvantages
resulting from the large pixel size, such as high gain and therefore higher
correlated noise, longer recovery time, lower dynamic range, and higher bias
current. Adding the radiation environment as an additional criterion, a low
excess bias voltage (overvoltage, $\Delta V$) is preferred to reduce the effect
of increasing the dark count rate (DCR) and correlated noise, as low DCR and low
correlated noise allow low noise rejection thresholds. In summary, small pixel
size and low $\Delta V$ are advantageous in all aspects except PDE.
In the presentation we will present an update on our current understanding of
the very promising development.
| Speaker Confirmation | Yes |
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