KM3NeT Collaboration Research Articles

Measurement of light scattering in deep sea

The deep-sea neutrino telescope in the Mediterranean Sea, being prepared by the KM3NET collaboration, will contain thousands of optical sensors to readout. The accurate knowledge of the optical properties of deep-sea water is of great importance for the neutrino event reconstruction process. In this study we describe our progress in designing an experimental setup and studying a method to measure the parameters describing the absorption and scattering characteristics of deep-sea water. Three PMTs will be used to measure in situ the scattered light emitted from six laser diodes in three different wavelengths covering the Cherenkov radiation spectrum. The technique for the evaluation of the parameters is based on Monte Carlo simulations and our results show that we are able to determine these parameters with satisfying precision.

Status of KM3NeT

The recent observation of cosmic neutrinos by IceCube has pushed the quest towards the identification of cosmic sources of high-energy particles. The KM3NeT Collaboration is now ready to launch the massive construction of detection units to be installed in deep sea to build a km-cubic size neutrino telescope. The main elements of the detector, the status of the project and the expected perfomances are briefly reported.

KM3NeT-ARCA project status and plan

The KM3NeT Collaboration aims at building a research infrastructure in the depths of the Mediterranean Sea hosting a cubic kilometre neutrino telescope. The KM3NeT/ARCA detector is the ideal instrument to look for high-energy neutrino sources thanks to the latitude of the detector and to the optical characteristics of the sea water. The detector latitude allows for a wide coverage of the observable sky including the region of the Galactic centre and the optical sea water properties allow for the measure of the neutrino direction with excellent angular resolution also for cascade events. The technologically innovative components of the detector and the status of construction will be presented as well as the capability it offers to discover neutrinos.

KM3NeT Neutrino Telescope 1-ns Resolution Time To Digital Converters

The KM3NeT collaboration aims the construction of a multi-km3 high- energy neutrino telescope in the Mediterranean sea consisting of thousands of glass spheres, each of them containing 31 photomultiplier of small photocathode area. The main digitization system is composed by 31 Time to Digital Converter channels with 1-ns resolution embedded in a Field Programmable Gate Array. An architecture with low resource occupancy has been chosen allowing the implementation of other instrumentation, communication and synchronization systems on the same device. The 4-oversampling technique with two high frequency clocks working in opposed phases has been used together with an asymmetric FIFO memory. In the present article the architecture and the first results obtained with the Time to Digital Converters are presented.

Predicted sensitivity of the KM3NeT/ARCA detector to a diffuse flux of cosmic neutrinos

The KM3NeT Collaboration has started the construction of a research infrastructure hosting a network of underwater neutrino detectors in the Mediterranean Sea. Two instruments based on the same technology are being built: KM3NeT/ORCA to measure the neutrino mass hierarchy and to study atmospheric neutrino oscillations and KM3NeT/ARCA to detect high-energy cosmic neutrinos both in diffuse and point source mode. The excellent angular resolution of the ARCA detector, with an instrumented volume of about one Gton, will allow for an unprecedented exploration of the neutrino sky searching for neutrinos coming from defined sources of sky regions, like the Galactic Plane and the Fermi Bubbles. It will also look for diffuse high energy neutrino fluxes following the indication provided by the IceCube signal. This contribution will report on the sensitivity of the KM3NeT/ARCA telescope with particular attention to the region of the Galactic Plane. Comparisons with theoretical expectations are also discussed.

KM3NeT Digital Optical Module electronics

The KM3NeT collaboration is currently building of a neutrino telescope with a volume of several cubic kilometres at the bottom of the Mediterranean Sea. The telescope consists of a matrix of Digital Optical Modules that will detect the Cherenkov light originated by the interaction of the neutrinos in the proximity of the detector. This contribution describes the main components of the read-out electronics of the Digital Optical Module: the Power Board, which delivers all the power supply required by the Digital Optical Molule electronics; the Central Logic Board, the main core of the read-out system, hosting 31 Time to Digital Converters with 1 ns resolution and the White Rabbit protocol embedded in the Central Logic Board Field Programmable Gate Array; the Octopus boards, that transfer the Low Voltage Digital Signals from the PMT bases to the Central Logic Board and finally the PMT bases, in charge of converting the analogue signal produced in the 31 3” PMTs into a Low Voltage Digital Signal.

Status of the central logic board (CLB) of the KM3NeT neutrino telescope

The KM3NeT collaboration aims at the construction of a multi-km3 high-energy neutrino telescope in the Mediterranean Sea consisting of thousands of glass spheres, each of them containing 31 photomultiplier of small photocathode area. The readout and data acquisition system of KM3NeT has to collect, treat and send to shore, the enormous amount of data produced by the photomultipliers, the acoustics sensor and the rest of the instrumentation. The electronics design includes a multiboot module which allows for the re-configuration of the nodes of the telescope remotely from the shore station. All the modules and subsystems are controlled by two embedded microprocessors, implemented on a Kintetx-7 FPGA, and complex embedded software.

High resolution time to digital converter for the KM3NeT neutrino telescope

The KM3NeT collaboration aims at the construction of a multi-km3 high-energy neutrino telescope in the Mediterranean Sea consisting of thousands of glass spheres, each of them containing 31 photomultipliers of small photocathode area. The readout and data acquisition system of KM3NeT has to collect, treat and send to shore, the enormous amount of data produced by the photomultipliers. For this purpose, 31 high-resolution time-interval measuring channels based on time to digital converter are implemented on the field-programmable gate arrays. Architectures with low resources occupancy are desirable allowing the implementation of other instrumentation, communication and synchronization systems on the same device. The required resolution to measure both, time of flight and time-stamp must be 1 ns. A 4-Oversampling technique with two high frequency clocks and an asymmetric FIFO memory is used to achieve this resolution. The proposed firmware has been developed in Xilinx Kintex-7.

The KM3NeT neutrino telescope: Status and prospects

The KM3NeT Collaboration intends to build and operate a deep-sea research infrastructure that will host as its main facility a neutrino telescope of several cubic kilometres. The infrastructure will be distributed in three sites located near Toulon, France (40km offshore and seabed at 2500m), Capo Passero (80km offshore and seabed at 3500m) and Pylos, Greece (20km offshore and seabed between 2500 and 5000m). In this contribution we describe the technological choices made for the basic components of the three-dimensional array of photo-sensitive devices in which the telescope will consist. The Digital Optical Modules (DOMs) will use a 17in. pressure-resistant sphere to accommodate 31 photomultipliers (PMTs) with a 3in. photocathode each. These DOMs will be installed in detector units (DUs) consisting of vertical strings anchored to the seabed and kept taut by the appropriate buoyancy. These DUs will be deployed by means of launching vehicles that will allow several of them to be deployed in the same campaign. The main features of the telescope and its technical components, the science it can do and the recent progress made towards its construction will be described here.

Time over threshold electronics for an underwater neutrino telescope

The use of time over threshold (ToT) digitization techniques for the treatment of the output signal of the PMTs of the KM3NeT detector is under consideration by the KM3NeT collaboration. In this technique the leading and trailing edge of the signal above a certain threshold are time stamped and the corresponding times are sent to the onshore acquisition system. More information can be obtained by applying the same scheme at multiple threshold levels. In this note, we present the efficiency of such a digitization technique applied to signals provided by the HEllenic LYceum Cosmic Observatories Network (HELYCON) extensive air shower detector. The hardware used has been designed by the Hellenic Open University (HOU) group and it is based on a high precision time to digital converter (HPTDC) chip developed at CERN and offering up to 32 channels with a digitization accuracy of 100 ps. We describe the operation and performance of this electronics and we evaluate the reconstruction accuracy of PMT signals using data collected from Extensive Air Showers. Finally, we report on our plans to use this electronics on Optical Modules proposed to be used in KM3NeT.

KM3NeT: Optimization studies for a cubic kilometer neutrino detector

In the KM3NeT Collaboration an important task is the simulation of the detector performance which aims at the optimization of the detector design. In this work the effect of two important items are studied: the PMT photocathode quantum efficiency and the effect of the bar length of a three-dimensional detection units. Simulation studies including the improved PMT photocathode quantum efficiency show that, especially at energy below 100 TeV, the increasing of the neutrino effective area is important. Moreover, simulations that optimize the geometry of one of the detection units proposed in KM3NeT are presented. In particular an increase in the effective areas for longer bars is observed.