arXiv subjects

Esteban Currás-Rivera

Publications and source records attributed to Esteban Currás-Rivera.

4 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

Defects and acceptor removal in 60Co γ-irradiated p-type silicon

Boron-doped silicon detectors used in high radiation environments like the future HL-LHC show a degradation in device performance due to the radiation induced deactivation of the active boron dopant. This effect, known as the so-called Acceptor Removal Effect (ARE), depends on particle type, particle energy and radiation dose and is usually explained by the formation of boroninterstitial - oxygen-interstitial (BiOi) defects that induce a donor-type defect level in the upper part of the Si band gap. Here we present defect characterization studies using Thermally Stimulated Current technique (TSC) and Deep Level Transient Spectroscopy (DLTS) on a set of epitaxially grown p-type silicon diodes of different resistivity, irradiated with 60Co γ-rays. We used the defect parameters (activation energy, charge carrier capture cross sections and defect concentration) obtained from DLTS experiments for modeling the corresponding TSC spectra, and subsequently compared those with the experimental TSC results. This approach shows that the di-vacancy which is well characterized by DLTS correlates with the so-far unspecified charge emission signal of the X-defect that partially overlaps with the BiOi peak in TSC spectra. Additionally, in order to evaluate the impact of BiOi defect formation on the macroscopic properties of the device, we compared the BiOi defect concentration with the change in the effective carrier concentration Neff obtained from C-V measurements. It shows that the variations in Neff are about twice the changes in the BiOi concentration, which is in perfect consistency with the assumption of boron deactivation by the formation of the BiOi donor in irradiated p-type Si.

hep-ex↗

arXiv2025

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↗

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↗