arXiv subjects

V. Buchakchiev

Publications and source records attributed to V. Buchakchiev.

3 recordsLinked to original sources

arXiv2025

Characterization of the large-size NDL EQR20 silicon photomultipliers

Unlike most commercially available silicon photomultipliers (SiPMs), EQR20 SiPMs produced by the Novel Device Laboratory (NDL) avoid using individual resistors to quench the avalanche multiplication of the microcells. Instead, bulk resistance of the epitaxial silicon layer is used, and the signal is directly collected at a common anode plane. This allows for the fabrication of SiPMs as large as 6.24 x 6.24 mm^2 while keeping the recovery time below {\tau} = 25 ns. These devices can be composed of microcells with 20 micrometer pitch while reaching PDE above 50% and 10^6 gain at 5 V overvoltage. On the other hand, a crosstalk level from 20% to 40% is observed for overvoltages from 3 V to 5 V. Moreover, significant pulse shape distortion is observed for pulses above ~100 pC, corresponding to microcell occupancy of a few percent. This work provides an independent determination of the performance parameters of the EQR20 11-6060D-S SiPMs. Influence of the pulse shape distortion is discussed from the perspective of the applicability of these devices to the scintillator-based forward hadron calorimeter (FoCal-H) of the ALICE apparatus at CERN.

physics.ins-det↗

arXiv2024

Application of the VMM ASIC for SiPM-based calorimetry

Highly integrated multichannel readout electronics is crucial in contemporary particle physics experiments. A novel silicon photomultiplier readout system based on the VMM3a ASIC was developed, for the first time exploiting this chip for calorimetric purposes. To extend the dynamic range the signal from each SiPM channel was processed by two electronics channels with different gain. A fully operational prototype system with 256 SiPM readout channels allowed the collection of data from a prototype of the ALICE Forward Hadron Calorimeter (FoCal-H). The design and the test beam results using high energy hadron beams are presented and discussed, confirming the applicability of VMM3a-based solutions for energy measurements in a high rate environment.

physics.ins-det↗

arXiv2023

Performance of the electromagnetic and hadronic prototype segments of the ALICE Forward Calorimeter

We present the performance of a full-length prototype of the ALICE Forward Calorimeter (FoCal). The detector is composed of a silicon-tungsten electromagnetic sampling calorimeter with longitudinal and transverse segmentation (FoCal-E) of about 20$X_0$ and a hadronic copper-scintillating-fiber calorimeter (FoCal-H) of about 5$\lambda_{\rm int}$. The data were taken between 2021 and 2023 at the CERN PS and SPS beam lines with hadron (electron) beams up to energies of 350 (300) GeV. Regarding FoCal-E, we report a comprehensive analysis of its response to minimum ionizing particles across all pad layers. The longitudinal shower profile of electromagnetic showers is measured with a layer-wise segmentation of 1$X_0$. As a projection to the performance of the final detector in electromagnetic showers, we demonstrate linearity in the full energy range, and show that the energy resolution fulfills the requirements for the physics needs. Additionally, the performance to separate two-showers events was studied by quantifying the transverse shower width. Regarding FoCal-H, we report a detailed analysis of the response to hadron beams between 60 and 350 GeV. The results are compared to simulations obtained with a Geant4 model of the test beam setup, which in particular for FoCal-E are in good agreement with the data. The energy resolution of FoCal-E was found to be lower than 3% at energies larger than 100 GeV. The response of FoCal-H to hadron beams was found to be linear, albeit with a significant intercept that is about factor 2 larger than in simulations. Its resolution, which is non-Gaussian and generally larger than in simulations, was quantified using the FWHM, and decreases from about 16% at 100 GeV to about 11% at 350 GeV. The discrepancy to simulations, which is particularly evident at low hadron energies, needs to be further investigated.

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