KM3NeT: a project for an underwater cubic kilometre neutrino telescope

R. Coniglione INFN-LNSTEV PA Paris 19-23 July 2010

KM3NeT: a project for an underwater cubic kilometre neutrino telescope

R. Coniglione INFN-LNS for KM3NeT collaboration

The KM3NeT consortium aims at developing a deep-sea research infrastructure in the

Mediterranean Sea. The construction of a multi-cubic-kilometre Cherenkov telescope for

neutrinos with energies above 100 GeV is the principal KM3NeT goal

•Introduction•Main objectives•The KM3NeT Technical Design Report•Telescope physics performance•New developments•Summary


KM3NeT and the international context

High energy neutrino telescope world map

ANTARES, NEMO, NESTORjoined efforts to preparea km3-size neutrino telescope in the Mediterranean Sea: KM3NeT

IceCubeIC79 taking data since 2010IC59 data analysis started

AntaresTaking data in its final configuration (12 lines) since may 2008.5 lines data analyzed and ready to be published


The KM3NeT consortium

The KM3NeT consortium includes 40 Institutes from 10 European Countries (Cyprus, France, Germany, Greece, Ireland, Italy, The Netherlands, Rumania, Spain, U.K.)

KM3NeT Design Study (DS) -> define the telescope design and outline the main technological optionsApproved under the 6° FP (funded by EC for the period 2006-2009) Conceptual Design Report (CDR) published in 2008

(http://www.km3net.org/public.php)Activity of DS culminated with the publication of the Technical Design Report

(TDR) that outlines the main technological options for the construction, deployment and maintenance of a deep sea neutrino telescope (http://www.km3net.org/public.php) (TDR contents frozen in November 2009)

KM3NeT Preparatory Phase (PP) -> define legal, governance and funding aspects, production planes for the detector elements, infrastructure features and prototype validation will be also definedApproved under the 7° FP (funded by EC for the period 2008-2012)


Neutrino will provide unique info on High Energy Universe

on the origin of UHE cosmic rays (astrophysics, cosmology and particle physics)on the high energy gamma production mechanism (hadronic and/or leptonic)on the source dense inner core

Neutrino observation can be connected with the observed gamma fluxes for sources with low matter density while new high density sources can be observed

Motivation for the high energy neutrino detection


KM3NeT main objectives

Central physics goals:-Investigate neutrino “point sources” in the 1-100 TeV energy regime galactic ->Supernova Remnants, Microquasars… extragalactic -> Active Galactic Nuclei, Gamma Ray Bursts-Complement IceCube field of view-Exceed IceCube sensitivity

Other important physics items:- High energy diffuse neutrino flux detection- Indirect search of Dark Matter- Neutrino particle physics aspects- Exotics (Magnetic Monopoles, Lorentz invariance violation, …)

Interdisciplinary research- geophysics, oceanography, marine biology, …

Implementation requirements:• Construction time ≤5 years• Operation over at least 10 years


KM3NeT sky view

2 downward coverage assumed

>75%>25%

KM3NeT complements the IceCube field of view KM3NeT observes a large part of the sky (~3.5)

At the Mediterranean sea latitude the source visibility can be less than 24h


Neutrino detection principle

Interaction

point

• Upward-going neutrinos interact in rock or water ( is the golden channel for astronomy)

• Emerging charged particles (in particular muons) produce Cherekov light in water at 43° with respect to the neutrino direction

• Light detection by array of

photomultipliers

• From photon arrival times and PMT positions is possible to reconstruct the muon direction Detection volume of the order of 5 km3 to exceed IceCube sensitivity by a

substantial factor

43°

c


Technical items

The telescope consists of 3D array of photo-sensors supported by vertical structures (DU) connected to a seabed with a cable network

The construction of a deep sea neutrino telescope is technically highly challenging

Very high pressureEnvironment chemically aggressiveDeployment operation safe, robust and precise

Technical itemsOptical Modules Front-end electronicsReadout, data acquisition, data transportMechanical structures, backbone cableGeneral deployment strategySea-bed network: cables, junction boxesCalibration devicesShore infrastructureAssembly, transport, logisticsRisk analysis and quality control

Requirements

Cost-effective Reliable Producible Easy to deploy


Other issues addressed in the Design Study

Site characterization:• Characterization of the site and measure of the water properties optical background, currents, sedimentation, water properties (absorption and

scattering lengths….)

Simulation:- Detector performances (sensitivity and discovery fluxes) optimizing the

detector parameters

- Earth and Sea science requirements:• Define the infrastructure needed to implement multidisciplinary

science nodes (marine biology, geology/geophysics, oceanography, environmental studies, alerts, …)


Optical modules

Two alternative solutions in the TDR for OM

Single-PMT Optical Module8-inch PMT with 35% quantum efficiencyinside a 13 inch glass sphere

Evolution from pilot projects

Multi-PMT Optical Module31 small PMTs (3-inch) inside a 17 inch glass sphere

• 31 PMT bases (total ~140 mW)

• Cooling shield and stem

First full prototype ready at the end of 2010


Optical modules

Two alternative solutions in the TDR for OM

Single-PMT Optical ModuleAdvantages

Multi-PMT Optical ModuleAdvantages

•photocathode surface greater than 3 8-inch PMTs

•insensitive to the Earth’s magnetic field -> no mu-metal shielding

•single-photon from multi-photon hits separation

•information on the arrival direction of Cherenkov light-> better track reconstruction

• large angular acceptance

• good timing response

• well known technology


Front-end electronics: Time-over-Threshold

Common solutions in the TDR for the front-end electronics


Detection Units

Three alternative solutions in the TDR for DUs

Flexible tower with horizontal bars equipped with single-PMTs or multi-PMT OMs

Triangular arrangements of OMs with single-PMTs or multi-PMT

Evolution of the ANTARES storey

Slender stringVertical sequence of multi-PMTs OMs

Simulations indicate that local 3D OM arrangement resolve ambiguities in the reconstruction of the muon azimuthal angle


Deployment strategy

Common deployment strategy in the TDRMain deployment concepts • Compact package• Self unfurling• Connection to seabed network by Remotely Operated Vehicle

Spherical deployment structure for string with single OM with multi-PMT

The packed flexible tower(20 storey)

Successful deployment test in February 2010 Successful

deployment test in December 2009


KM3NeT: an artistic view

Primary Junction box Secondary Junction boxes

Detection Units

Electro-optical cable


Simulations: optimization studies

Bar length optimization Optimization of Detection Unit separation

Examples for the flexible tower

Low energy region100GeV<E<500 GeV

Quality cuts applied -rec~ 2° (close to the -

)

Point like sources3TeV<E<100 TeV

Quality cuts applied -rec~ 0.4°(close to the search cone radius)

Diffuse flux studies & GRBE>100 TeV

No quality cuts applied -rec 0.9°

ratio of the effective area relative to 3m ratio of the effective area relative to 100m



Sensitivity ratio for point like source - 1 year – =-60°

Flexible tower

180 m preferred DU distance

Final bar length choice is a compromise between physical performance and technical constraints

Bar length

Detection unit separation


Sensitivity to point source (flux E-2) vs declination for one year of observation time

Full KM3NeT detectors made of the three DU configurations at the same cost were considered in the simulations

Similar sensitivity per euro for the three configurations

Black Slender stringRed Flexible towerGreen Triangles

A detector with a total cost of about 220M€ is required to surpass the performance of IceCube by a substantial factor

Simulation results

conceptNumber of DU for 220M€

Flexible tower with 6 8” PMT per bar 20 bars

310(2x154)

Slender strings20 floors with 1 multi-PMT per floor

620 (2X310)

Triangles 6 8” PMT per floor 20 floors

254(2x127)


KM3NeT: effective area & resolution

☐Quality Cuts applied (0.2°@30TeV) Quality Cuts optimized for sensitivity

Neutrino effective areaDetector resolutionMedian of rec

Kinematics

median of the distribution


KM3NeT: sensitivity & discovery

KM3NeT sensitivity 90%CLKM3NeT discovery 5 50%IceCube sensitivity 90%CLIceCube discovery 5 50% 2.5÷3.5 above sensitivity flux. (extrapolation from IceCube 40 string configuration)

binned method

unbinned method

| Observed Galactic TeV- sources (SNR, unidentified, microquazars) F. Aharonian et al. Rep. Prog. Phys. (2008)Abdo et al., MILAGRO, Astrophys. J. 658 L33-L36 (2007) Galactic Centre

Sensitivity and discovery fluxes for point like sources with a E-2 spectrum for 1 year of observation time


Developments after the TDR

In the recent months developments towards a technology convergence on a unique design

• “bar” option with horizontal extent and 6 8-inch PMTs– Optimised design and plan for extensive deployment tests

defined

• Study of the advantages offered by a “hibrid” solution– DU with horizontal extent– Multi-PMT Optical Module

• Multi-PMT option– Needs validation of technology and integration procedures– Common development of the multi-PMT Optical Module and its

implementation on the tower– Optimization of simulation of the detector performance ongoing


Flexible tower DU with 6 13” spheres: stacking concept

Height = 1.43 m


Flexible tower DU with 2 17” OM: preliminary storey design


Summary

• A design for the KM3NeT neutrino telescope complementing the IceCube field of view and surpassing it in sensitivity by a substantial factor is presented

• The required sensitivity can be achieved within an overall budget of ≈ 250 M€

• Staged implementation, with increasing discovery potential, is technically possible

• Convergence process toward a unique technical design under way

• Development plan for qualification of a pre-production model of the detection unit defined

• Remaining technical decisions have to be taken within the next spring

• Readiness for construction expected at the end of the Preparatory Phase (march 2012)

• Installation could start in 2013 and data taking soon after


The end



Sensitivity ratio for point like source - 1 year – =-60°

Flexible tower

180 m preferred DU distance

Final bar length choice is a compromise between physical performance and technical constraints

Bar length

Detection unit separation

=-2.2

=-2


Theta versus declination

Mediterranean sea latitude 36°

-80-70

-60-50

=-40

-30-20

-10

0 +20+40 +50

Above the horizon Below the horizon

Near the horizon the effect of Earth absorption is reduced for high energy neutrinos

Documents

KM3NeT: a project for an underwater cubic kilometre neutrino telescope