arXiv subjects

Guido Haefeli

Publications and source records attributed to Guido Haefeli.

5 recordsLinked to original sources

arXiv2026

Cryogenic operation of neutron-irradiated silicon photomultiplier arrays up to 1e14 neq/cm^2

In the context of the Scintillating Fibre (SciFi) Tracker for the LHCb Upgrade 2, radiation-induced damage in silicon photomultipliers (SiPMs) has been studied over a wide temperature range, from room temperature down to 100 K. With the LHCb detector Upgrade 1, installed during the LHC's Long Shutdown 2 (LS2) (2019-2021), the first large-scale SciFi tracker read out by multichannel silicon photomultipliers (SiPMs) was constructed, installed, and has been operated ever since. A major challenge for the SciFi tracker is the neutron radiation at the SiPMs' location. At the end of the lifetime of the Upgrade 1 detector, the expected neutron fluence for the SiPMs will reach 6e11 neq/cm^2. Cryogenic operation is being investigated to mitigate even higher radiation-induced damage for Upgrade 2, where the total neutron fluence is expected to reach 3e12 neq/cm^2. A large set of custom SiPM arrays, varying in pixel size, electric field configuration, and doping implant concentration, developed by FBK and Hamamatsu, were tested after neutron irradiation. Characterisation was performed in a dedicated cryogenic test setup, where the operating temperature was varied over a wide range. Key performance parameters such as breakdown voltage, gain, dark count rate, optical crosstalk, and afterpulsing were characterised as functions of temperature, overvoltage, and neutron fluence. The result is a precise assessment of radiation damage for state-of-the-art technology from two leading SiPM manufacturers, allowing the results to be transferred to other SiPM applications.

physics.ins-det↗

arXiv2025

Cryogenic operation of silicon photomultiplier arrays

The LHCb experiment at CERN has been upgraded for the Run 3 operation of the Large Hadron Collider (LHC). A new concept of tracking detector based on Scintillating Fibres (SciFi) read out with multichannel silicon photomultipliers (SiPMs) was installed during its upgrade. One of the main challenges the SciFi tracker will face during the Run 4 operation of the LHC is the higher radiation environment due to fast neutrons, where the SiPMs are located. To cope with the increase in radiation, cryogenic cooling with liquid nitrogen is being investigated as a possible solution to mitigate the performance degradation of the SiPMs induced by radiation damage. Thus, a detailed performance study of different layouts of SiPM arrays produced by Fondazione Bruno Kessler (FBK) and Hamamatsu Photonics K.K. is being carried out. These SiPMs have been designed to operate at cryogenic temperatures. Several SiPMs have been tested in a dedicated cryogenic setup down to 100 K. Key performance parameters such as breakdown voltage, dark count rate, photon detection efficiency, gain and direct cross-talk are characterized as a function of the temperature. The main results of this study are going to be presented here.

hep-ex↗

arXiv2024

Microlens-enhanced SiPMs

A novel concept to enhance the photo-detection efficiency (PDE) of silicon photomultipliers (SiPMs) has been applied and remarkable positive results can be reported. This concept uses arrays of microlenses to cover every second SiPM pixel in a checkerboard arrangement and aims to deflect the light from the dead region of the pixelised structure towards the active region in the center of the pixel. The PDE is improved up to 24%, external cross-talk is reduced by 40% compared to a flat epoxy layer, and single photon time resolution is improved. This detector development is conducted in the context of the next generation LHCb scintillating fibre tracker located in a high radiation environment with a total of 700'000 detector channels. The simulation and measurement results are in good agreement and will be discussed in this work.

physics.ins-det↗

arXiv2024

The CuboDAQ Data Acquisition System

CuboDAQ is a custom data acquisition system to read out SiPM-based detectors. It features electronic boards to digitize the SiPMs signal, an FPGA-based system-on-module board, the connectivity to transmit the data to a central server, and all the software necessary to operate them. The front-end is based on the TOFPET2 ASIC, produced by PETsys, connected to a custom board, featuring an Enclustra Mercury SA1 module with a Cyclone~V FPGA. Multiple boards can be operated synchronously by distributing the clock and synchronous reset signals from a central source. The system features a complete software framework to calibrate and monitor the detectors, to acquire and process data and to perform track reconstruction. The CuboDAQ system performance has been evaluated in different scenarios and can cope with sustained rates of above $4\cdot 10^6$ hits/s, with peaks of more than $7\cdot 10^6$ hits/s. This system has been employed for the readout of the SND@LHC detector at CERN, a testbeam telescope and lab setups.

physics.ins-det↗

arXiv2018

Characterisation of silicon photomultipliers based on statistical analysis of pulse-shape and time distributions

A detailed and accurate characterisation of silicon photomultiplier detectors is required for a better understanding of the signal and noise in many applications. The collected information is a valuable feedback to the manufacturers in their attempt to improve the performances. In this paper, we provide a detailed description of how to characterise these photo-detectors. The correlated noise probabilities, the important time constants and the photon detection efficiency are obtained with a statistical analysis of pulse-shape and time distributions. The method is tested with different detectors. The quench resistor, the breakdown voltage and the dark count rate are measured from IV characteristics.

physics.ins-det↗