Isabella Amore Laboratori Nazionali del Sud - INFN, Catania International School of Cosmic Ray...

Isabella Amore Laboratori Nazionali del Sud - INFN, Catania

International School of Cosmic Ray Astrophysics15th Course: "Astrophysics at Ultra-high Energies"

NEMO: a project for a km3 underwater detector for astrophysical neutrinos in the

Mediterranean Sea

Isabella Amore

20-27 June 2006, EriceEttore Majorana Centre


Why Neutrino Astronomy?

gammas 0,01-1 Mpc

protons E>1019 eV10 Mpc

High energy neutrinos

Astrophysicalsource

We want to measure neutrinos coming from astrophysical sources

1 parsec (pc) 3 ligth years

5 Gpc

Closest AGNs

Galactic radius (15 kpc)

TeV PeV EeV

Neutrinos traverse space without being deflected or absorbed:

– They can reach the Earth from cosmological sources– They point back to their sources– They allow to view into dense environments


Status of collaborationsBAIKAL, AMANDA: taking dataNESTOR, ANTARES, NEMO R&D: under constructionICECUBE: completion expected in 2010KM3NET – Mediterranean : EU Design Study 2006-2008

AMANDAICECUBE

BAIKAL

ANTARES

2400 m

NESTOR

3800 m

NEMO

3500 m

• In order to obtain the whole sky coverage 2 telescopes must be built

• The Galactic Centre is observable only from the Northern Hemisphere

Small scale detectors and demonstrators

km3 scale telescopes


The NEMO collaboration

INFNBari, Bologna, Catania, Genova, LNF, LNS, Napoli, Pisa, RomaUniversitiesBari, Bologna, Catania, Genova, Napoli, Pisa, Roma “La Sapienza”

CNRIstituto di Oceanografia Fisica, La SpeziaIstituto di Biologia del Mare, VeneziaIstituto Sperimentale Talassografico, Messina

Istituto Nazionale di Geofisica e Vulcanologia (INGV)

Istituto Nazionale di Oceanografia e Geofisica Sperimentale (OGS)

Istituto Superiore delle Comunicazioni e delle Tecnologie dell’Informazione (ISCTI)

More than 70 researchers from INFN and other Italian Institutes


NEMO R&D activities towards the Mediterranean km3

Site selection and long term monitoring

Feasibility study of the km3 detector

Installation of small scale prototypes

Realization of a marine infrastructure for the km3


The Capo Passero deep sea site

• It is located in a wide abyssal plateau far from shelf breaks and geologically stable.

• The average depth is 3500 m, the distance from shore is about 100 km.

• Optical properties of deep sea water are the best measured among investigated sites (absorption length close to optically pure water astro-ph\0603701)

• Optical background is low (30 kHz on 10’’ PMT at 0.3 s.p.e. threshold) and mainly due to 40K decay since the bioluminesce activity is extremely low.

• Underwater currents are very low (2.5 cm/s) and stable.

After eight years of activity in seeking and monitoring abyssal sites in the Mediterranean Sea the NEMO collaboration has chosen a deep sea site about 100 km SE of Capo Passero, in Sicily.The site has been proposed to ApPEC on january 2003 as candidate site for the installation of the km3.


Seawater optical properties

Optical properties have been measured in Capo Passero since 1998

Profiles as a function of depth of oceanographic and optical properties in Capo Passero

• Seasonal dependence of oceanographical

(Temperature and Salinity) and optical

(absorption and attenuation) properties

has been studied in Capo Passero

• Variations are only observed in shallow

water layers

• Seasonal dependence of oceanographical

(Temperature and Salinity) and optical

(absorption and attenuation) properties

has been studied in Capo Passero

• Variations are only observed in shallow

water layers

• Absorption lengths measured in Capo Passero are close to the optically pure sea water data

• Differences between Toulon and Capo Passero are observed for the blue light absorption

• Absorption lengths measured in Capo Passero are close to the optically pure sea water data

• Differences between Toulon and Capo Passero are observed for the blue light absorption

temperature

salinity

a440 c440

absorption @ 440nm absorption @ 440nm

attenuation @ 440nm attenuation @ 440nm

Lc=35.5 m

La=66.5 m


Optical background was measured

in Capo Passero @ 3000 m depth.

Data are consistent with 30 kHz background on

10”PMT at 0.3 spe

(mainly 40K decay, very few bioluminescence).

Optical data are consistent with biological measurements:

No luminescent bacteria have been observed in Capo Passero

below 2500 m

Optical background in Capo Passero

40K

Baseline rate~ 30 kHz

15

20

25

30

35

0 7 14 21 28 35 42 49

Co

un

tin

g r

ates

(kH

z)

0.0%

0.5%

1.0%

1.5%

2.0% Tim

e abo

ve 200 kHz

Days

30 kHz


Feasibility study for the km3 detector

main EO cablemain Junction Box

secondary JB

“tower”

Detector architecture has been studied in order to

Reduce the number of structures to reduce the number of underwater connections and allow operation with a ROV

Detector modularity

9 x 9 = 81 “Towers” with 3 dimensional and non homogeneous distribution of sensors

Conceptual detector layout


The NEMO tower

Height:compacted 15:20 mtotal 750 minstrumented 600 mn. beams 16 to 20n. PMT 64 to 80Beams:length 15 mspacing 40 m

The tower is a semi-rigid 3D

structure designed to allow easy

deployment and recovery.

High local PMT density is designed

to perform local trigger.750

m

10’’ PMTs


Expected detector performaces

SensitivitySensitivity to a Ev

-2 neutrino spectrum from point like sources

NEMO 81 towers 140m spaced - 5832 PMTsIceCube 80 strings 125m spaced - 4800 PMTs

Geometry “flexibility”Effective area for different detector geometries

spacing spacingtowers floors140 m 40 m

300 m 40 m

C. Distefano, NEMO, astro-ph/0605067 R. Coniglione, NEMO astro-ph/0605068


Validation of technologies: NEMO Phase 1

The NEMO Collaboration is undergoing the Phase 1 of the project, installing a fully equipped

deep-sea facility to test prototypes and develop new technologies for the km3 detector.

Shore laboratory port of Catania

e.o. cable from shore

TSS Frame

To be completed in 2006

Junction Box

NEMO mini-tower(4 floors)

Deployed on Jan 2005

underwater e.o. cable10 OF 6 conductors

Underwater test site: 25 km E offshore Catania at 2000 m depth

Realizaton of a system hosting all key elements for the km3 detector:

Mechanical structures; Optical and environmental sensors; Electronics; Data

transmission system; Power distribution system; Acoustic positioning

system;Time calibration system


Sea operations January 2005


The NEMO test site: a multidisciplinary laboratory

The ODE stationGEOSTAR SN-1 deep sea station

First data from 2000 m• GEOSTAR SN-1, a deep sea station for on-line seismic and environmental monitoring by

INGV. The NEMO test site is the Italian site for ESONET (European Seafloor Observatory

NETwork);

• ODE (Ocean noise Detection Experiment), for on-line deep sea acoustic signals

monitoring (4 hydrophones hydrophones 30 Hz - 40 kHz measurement of noise bkg for

neutrino acoustic detection ).


The NEMO Phase 1: the underwater station

TSS Frame

Junction Box

NEMO mini-tower(4 floors, 16 OM)

300

m

Mini-Tower compacted

Mini-Tower unfurled

15 m

Al alloy

Buoy

e.o. connection

The mechanical structure is

under final assembly at the

NEMO Test Site shore

laboratory


The Junction Box

Fiberglass external vessel

Power vesselselectro-optical

connectors

The Junction Box hosts the data transmission and power distribution system.

The JB is made of an Al cage, an extrenal fiberglass vessel and 4 steel pressure vessels: PV1, PV2, PV3 and Trafo Vessel.The space between fiberglass and PV will be filled with silicone oil.This solution permits to separate the corrosion and the pressure resistance problems.

1 m


NEMO Phase 1: Floor DAQ chain

Hamamatsu 10" R7081 SEL 200 Msample/s

Floor Control Module Board:

Transmit OM and slow Control data (water parametres, OM position, internal sensors) to shore through Optical Fibre (DWDM technology)

Optical Module (OM)

PMT tube FEM board

Underwater electrical Cable

e.o. transceiver

Floor Control Module Board (FCMB)

Optical modules

Floor control module


The NEMO Phase 2 project in Capo Passero

Objectives- Realization of an underwater infrastructure at

3500 m on the Capo Passero site- Test of the detector structure installation

procedures at 3500 m- Installation of a 16 storey tower- Long term monitoring of the site

Status

- The EO cable (≈48 optical fibres, 30÷40 kW) will

be deployed within 2007- The shore laboratory acquired, now in

restoration


Summary and outlook

• Site selection– The Capo Passero site has been deeply studied: the results show that it is an excellent location for a km3 telescope

• Feasibility study

– All the critical detector components and their installation have been analysed in detail

• Present activity

– NEMO-Phase 1 in Catania: installation of a subset of the detector including all the critical components

• Future plans

– NEMO-Phase 2 : Underwater infrastructure @ 3500 m in Capo Passero

… A large international collaboration will build the Mediterranean km3


We are eagerly waiting for the start-up !

Isabella Amore Laboratori Nazionali del Sud - INFN, Catania International School of Cosmic Ray...

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