A sensor architecture for neutrino telescopes on behalf of the KM3NeT consortium Els de Wolf Thank you, Claudio!

Buoy OM 10 kV / 400V ~2.6 km slender strings 6000 optical modules ~100 MEuro Branch cable network on the seabed Junction box

Features of the architecture Flexible and slender string structure Optical fibre network for communication Single high pressure transition per storey Few (active) components in the deep ‐ sea No application specific components in the deep-sea No fault (leak)propagation from one storey to the other or from one string to the other One wet ‐ mateable connections per string  (Innovative deployment: 1/~15) Minimum of material in the deep sea ‘Low’ cost 3 reliability

Analysis of DUMAND/Antares/NEMO/Nestor Flexible string works Fibre network works Reliability can be further enhanced Costs can be reduced 4

Reliability analysis Minimise probability of water leaks  Minimise number of pressure transitions 5 1(2?) transition (1 OM) ~Same photocathode Electronics and all other instrumentation a single container 9 transitions (3 OMs + Hydrophone) 1 transition

multi-PMT optical module  No separate electronics container  Single pressure transition per storey (optical module = storey) 6 (talk Paul Kooijman)

7 Nikhef Open Day 10/10/2009 Temperature measurements in multi-PMT optical module

Sensor concept for readout&DAQ Laser light from shore is modulated in the (optical) module with the data through reflective modulators. Readout on heart-beat of laser pulses from shore  Front-end functionality moved to shore. 8 laser

Sensor architecture concept Unique optical connection between each module and the shore. 9 laser (talk Jelle Hogenbirk)

Reliability of readout/DAQ  Only few non-specific active components in the deep sea  No application-specific components in the deep sea 10 Designed to our specification by telecom technical consultancy company CIP, using their off the shelf and Bellcore certified items.

Communication network 10 Gb/s bandwidth, 50 GHz channel spacing Passive Optical Network using DWDM Fibre propagation time over 100 km measured with precision < 100 ps

Electro-optical backbone Flexible hose Oil filled, run at equipressure Break out at each storey Wet-mateable connection to node in branch cable 12 No propagation of failure of one storey to another (talk Eric Heine) First reference model

Mechanics of slender string  Minimum of material in the deep sea 13 Two dyneema ropes for mechanical strength Simple structure to support optical module

Slender string 20 storeys String master module included in break-out-box at storey 9 Low drag Relatively easy to deploy  Single wet ‐ mateable connection per string (innovative deployment: very few) 14 Buoy OM BOB & DWDM BOB Anchor Rope Storey 30 m 570m 100m EOC (2 fiber + 2 Cu) DU_CON (talk Eric Heine)

Realisation speed up Enlarge weather window for deployment  Compact and light deployment structures Increase deployment rate  Many strings in a single sea operation. Early start of construction strings  Can start while on-shore electronics is still in development 15

16 10 kV / 400V Junction box Sea floor: branch cables with nodes Compact deployment of strings Sea floor network of branch cables with nodes node

17 Unfurling of the string

18 Connect to node in the branch cable ~2.6 km slender strings 6000 optical modules ~100 MEuro

Effective area 19 Simulation and reconstruction effort started late, but is ongoing Preliminary results are promising. Claudio Kopper 130 m string distance Upgoing tracks only

Effective area compared to Antares 20 Antares EnergyAntaresFactor 100 GeV8x10 -5 m 2 -5 (?) 1 TeV0.005 m m TeV0.5 m 2 20 m TeV3m m PeV20 m m 2 25 Rough comparison

Summary and conclusions Sensor architecture with slender strings is feasible  Based on experience of pre-decessors  Designed for high reliable  Cost effective  Easy to deploy Further improvements  Improvement/avoidance wet-mateable connections  Reconstruction Preparatory phase  Prototype string mechanics  Prototype electro-optical cable  Detailing readout and DAQ  Design assembly lines for OM and string  Detailing seafloor network 21 Engineering effort together with industry started (first ideas documented)

Thank you!