32 research outputs found
A highly innovative design of a photomultiplier: prototypes, engineering and applications in astroparticle physics.
Photon detection represents a critical issue in the current generation of high-energy astroparticle physics experiments. Indeed, many experiments in this rapidly emerging field are based on the detection of the Cherenkov or fluorescence light produced after the passage of charged particles through transparent media like air, water or ice. For these applications, the quality of the experimental results is crucially related to the performances of the adopted photodetectors, for which therefore high efficiency, photon counting capability and large sensitive surface are required.
To date, this field is dominated by PhotoMultiplier Tubes (PMTs), a one-century-old technology that in the last decades has known a whirling evolution, leading to impressive improvements, especially in terms of quantum efficiency and gain, but affected by some intrinsic drawbacks that strongly limit its performances. Moreover, the next generation of experiments will set stricter requirements about photodetectors performances, in particular for what concerns photon counting capability and power consumption. For these reasons, in the last decades several alternatives to PMTs have been introduced.
In this context, an interesting solution is represented by the VSiPMT (acronym of Vacuum Silicon PhotoMultiplier Tube), a novel photodetector based on the combination of PMT and Geiger-mode Avalanche PhotoDiode (G-APD) technologies. Indeed, in such device the standard dynode chain of the PMT is replaced by a G-APD, operating in electron multiplier mode, thus matching large sensitive surface and high photon counting performances.
After years of preliminary work aimed at proving the feasibility of the VSiPMT, the encouraging results achieved convinced Hamamatsu Photonics, World leader company in PMT and SiPM manufacture, to realize some prototypes of the device. This thesis describes accurately all the phases of the VSiPMT project, with a particular focus on the results of the prototype characterization phase and on the possible application of the VSiPMT to the KM3NeT neutrino telescope
A new generation photodetector for astroparticle physics: the VSiPMT
The VSiPMT (Vacuum Silicon PhotoMultiplier Tube) is an innovative design we
proposed for a revolutionary photon detector. The main idea is to replace the
classical dynode chain of a PMT with a SiPM (G-APD), the latter acting as an
electron detector and amplifier. The aim is to match the large sensitive area
of a photocathode with the performance of the SiPM technology. The VSiPMT has
many attractive features. In particular, a low power consumption and an
excellent photon counting capability. To prove the feasibility of the idea we
first tested the performance of a special non-windowed SiPM by Hamamatsu (MPPC)
as electron detector and current amplifier. Thanks to this result Hamamatsu
realized two VSiPMT industrial prototypes. In this work, we present the results
of a full characterization of the VSiPMT prototype
STRAW-b (STRings for Absorption length in Water-b): the second pathfinder mission for the Pacific Ocean Neutrino Experiment
Since 2018, the potential for a high-energy neutrino telescope, named the
Pacific Ocean Neutrino Experiment (P-ONE), has been thoroughly examined by two
pathfinder missions, STRAW and STRAW-b, short for short for Strings for
Absorption Length in Water. The P-ONE project seeks to install a neutrino
detector with a one cubic kilometer volume in the Cascadia Basin's deep marine
surroundings, situated near the western shores of Vancouver Island, Canada. To
assess the environmental conditions and feasibility of constructing a neutrino
detector of that scale, the pathfinder missions, STRAW and STRAW-b, have been
deployed at a depth of 2.7 km within the designated site for P-ONE and were
connected to the NEPTUNE observatory, operated by Ocean Networks Canada (ONC).
While STRAW focused on analyzing the optical properties of water in the
Cascadia Basin, \ac{strawb} employed cameras and spectrometers to investigate
the characteristics of bioluminescence in the deep-sea environment. This report
introduces the STRAW-b concept, covering its scientific objectives and the
instrumentation used. Furthermore, it discusses the design considerations
implemented to guarantee a secure and dependable deployment process of STRAW-b.
Additionally, it showcases the data collected by battery-powered loggers, which
monitored the mechanical stress on the equipment throughout the deployment. The
report also offers an overview of STRAW-b's operation, with a specific emphasis
on the notable advancements achieved in the data acquisition (DAQ) system and
its successful integration with the server infrastructure of ONC.Comment: 20 pages, 11 figures, 2 table
Event reconstruction for KM3NeT/ORCA using convolutional neural networks
The KM3NeT research infrastructure is currently under construction at two
locations in the Mediterranean Sea. The KM3NeT/ORCA water-Cherenkov neutrino
detector off the French coast will instrument several megatons of seawater with
photosensors. Its main objective is the determination of the neutrino mass
ordering. This work aims at demonstrating the general applicability of deep
convolutional neural networks to neutrino telescopes, using simulated datasets
for the KM3NeT/ORCA detector as an example. To this end, the networks are
employed to achieve reconstruction and classification tasks that constitute an
alternative to the analysis pipeline presented for KM3NeT/ORCA in the KM3NeT
Letter of Intent. They are used to infer event reconstruction estimates for the
energy, the direction, and the interaction point of incident neutrinos. The
spatial distribution of Cherenkov light generated by charged particles induced
in neutrino interactions is classified as shower- or track-like, and the main
background processes associated with the detection of atmospheric neutrinos are
recognized. Performance comparisons to machine-learning classification and
maximum-likelihood reconstruction algorithms previously developed for
KM3NeT/ORCA are provided. It is shown that this application of deep
convolutional neural networks to simulated datasets for a large-volume neutrino
telescope yields competitive reconstruction results and performance
improvements with respect to classical approaches
Event reconstruction for KM3NeT/ORCA using convolutional neural networks
The KM3NeT research infrastructure is currently under construction at two locations in the Mediterranean Sea. The KM3NeT/ORCA water-Cherenkov neutrino de tector off the French coast will instrument several megatons of seawater with photosensors. Its main objective is the determination of the neutrino mass ordering. This work aims at demonstrating the general applicability of deep convolutional neural networks to neutrino telescopes, using simulated datasets for the KM3NeT/ORCA detector as an example. To this end, the networks are employed to achieve reconstruction and classification tasks that constitute an alternative to the analysis pipeline presented for KM3NeT/ORCA in the KM3NeT Letter of Intent. They are used to infer event reconstruction estimates for the energy, the direction, and the interaction point of incident neutrinos. The spatial distribution of Cherenkov light generated by charged particles induced in neutrino interactions is classified as shower-or track-like, and the main background processes associated with the detection of atmospheric neutrinos are
recognized. Performance comparisons to machine-learning classification and maximum-likelihood reconstruction algorithms previously developed for KM3NeT/ORCA are provided. It is shown that this application of deep convolutional neural networks to simulated datasets for a large-volume neutrino telescope yields competitive reconstruction results and performance
improvements with respect to classical approaches
The KM3NeT Digital Optical Module
KM3NeT is a European deep-sea multidisciplinary research infrastructure in the Mediterranean Sea. It will host a km3-scale neutrino telescope and dedicated instruments for long-term and continuous measurements for Earth and Sea sciences. The KM3NeT neutrino telescope is a 3-dimensional array of Digital Optical Modules, suspended in the sea by means of vertical string structures, called Detection Units, supported by two pre-stretched Dyneema ropes, anchored to the seabed and kept taut with a system of buoys. The Digital Optical Module represents the active part of the neutrino telescope. It is composed by a 17-inch, 14 mm thick borosilicate glass (Vitrovex) spheric vessel housing 31 photomultiplier tubes with 3-inch photocathode diameter and the associated front-end and readout electronics. The technical solution adopted for the KM3NeT optical modules is characterized by an innovative design, considering that existing neutrino telescopes, Baikal, IceCube and ANTARES, all use large photomultipliers, typically with a diameter of 8″ or 10″. It offers several advantages: higher sensitive surface (1260 cm2), weaker sensitivity to Earth's magnetic field, better distinction between single-photon and multi-photon events (photon counting) and directional information with an almost isotropic field of view. In this contribution the design and the performance of the KM3NeT Digital Optical Modules are discussed, with a particular focus on enabling technologies and integration procedure
A search for time dependent neutrino emission from microquasars with the ANTARES telescope
Results are presented on a search for neutrino emission from a sample of six microquasars, based on the data collected by the ANTARES neutrino telescope between 2007 and 2010. By means of appropriate time cuts, the neutrino search has been restricted to the periods when the acceleration of relativistic jets was taking place at the microquasars under study. The time cuts have been chosen using the information from the X-ray telescopes RXTE/ASM and Swift/BAT, and, in one case, the gamma-ray telescope Fermi/LAT. No statistically significant excess has been observed, thus upper limits on the neutrino fluences have been derived and compared to the predictions by models. Constraints have been put on the ratio of proton to electron luminosity in the jets
The KM3NeT Digital Optical Module
KM3NeT is a European deep-sea multidisciplinary research infrastructure in the Mediterranean Sea. It will host a km3-scale neutrino telescope and dedicated instruments for long-term and continuous measurements for Earth and Sea sciences. The KM3NeT neutrino telescope is a 3-dimensional array of Digital Optical Modules, suspended in the sea by means of vertical string structures, called Detection Units, supported by two pre-stretched Dyneema ropes, anchored to the seabed and kept taut with a system of buoys. The Digital Optical Module represents the active part of the neutrino telescope. It is composed by a 17-inch, 14 mm thick borosilicate glass (Vitrovex) spheric vessel housing 31 photomultiplier tubes with 3-inch photocathode diameter and the associated front-end and readout electronics. The technical solution adopted for the KM3NeT optical modules is characterized by an innovative design, considering that existing neutrino telescopes, Baikal, IceCube and ANTARES, all use large photomultipliers, typically with a diameter of 8″ or 10″. It offers several advantages: higher sensitive surface (1260 cm2), weaker sensitivity to Earth's magnetic field, better distinction between single-photon and multi-photon events (photon counting) and directional information with an almost isotropic field of view. In this contribution the design and the performance of the KM3NeT Digital Optical Modules are discussed, with a particular focus on enabling technologies and integration procedure
VSiPMT for underwater neutrino telescopes
Underwater neutrino telescopes are nowadays considered among the most important aims in the field of astroparticle physics. Their structure consists of a cubic-kilometer three-dimensional array of photosensitive devices aimed at the detection of the Cherenkov light emitted by charged particles produced by high energy neutrino interactions with the Earth. To date, a crucial role in this kind of experiments has been played by PhotoMultiplier Tubes (PMTs), however they suffer from many drawbacks such as linearity-to-gain relationship and difficulty in single photon counting. The next generation of experiments will require further improvements in photon detectors performances, therefore alternatives to PMTs are currently under study. In particular the most promising development in this field is represented by the rapidly emerging CMOS p-n Geiger-mode avalanche photodiode technology (G-APD or SiPM), that will allow the detection of highspeed single photons with high gain and linearity. In order to overcome the limit of small sensitive surfaces we suggest an innovative design for a modern hybrid, high gain, silicon based Vacuum Silicon Photomultiplier Tube (VSiPMT) based on the combination of a SiPM with a hemispherical vacuum glass PMT standard envelope. In this work we describe the full SiPM characterization realized by our group and we present the results of our Geant4-based simulations of electron backscattering over the SiPM surface. © 2012 Elsevier B.V. All rights reserved