Deep-sea neutrino telescopes Prof. dr. Maarten de Jong Nikhef / Leiden University

contents  Neutrino astronomy  Antares ‒prototype  KM3NeT ‒next generation neutrino telescope  issues, ideas

neutrinos  p Scientific motivation: – origin cosmic rays – creation& composition relativistic jets – mechanism cosmic particle acceleration – composition dark matter neutrino telescope Why neutrinos? – no absorption – no bending Neutrino astronomy

1960 Markov’s idea:  range of muon  detect Cherenkov light  transparency of water Use sea water as target/detector

How? muon wavefron t ~few km ~100 m muon travels with speed of light (300,000 km/s) → ns (10 km neutrino interaction

General layout light detection transmission of (all) data data filter real-time event distribution shore station 3-5 km 800 m km 1-2 km >1000 km

Antares  1997‒2005 – R&D – site explorations – measurements of water properties  2005‒2008 – construction-operation  2008‒2017 – operation prototype neutrino telescope ‒ 100 persons ‒ 25 M€

~2.5 km 500 m 250 Atm. ~200x200 m 2 12 lines 25 storeys / line Antares

Hydrophone acoustic positioning 10” PMT photon detection Electronics readout titanium frame mechanical support Optical beacon timing calibration ~1 m Detection unit

Dutch industry Gb/s transceiver DC–DC converter passive cooling

PMT 100 Mb/s e/o Ethernet switch 1 Gb/s e/o optical fiber (21) DWDM filter optical fiber (4) 40 km 5x15 m 5‒25x15 m CPU FPGA container deep-sea network penetrator (3) connector (3) penetrator (2) wet-matable connector (2) 1 km (40) junction box

data filter time Ethernet switch off-shore on shore CPU data flow

data filter time Ethernet switch off-shore on shore CPU data flow

data filter time Ethernet switch off-shore on shore CPU data flow

Antares  deep-sea infrastructure – 1 km PMTs, hydrophones, ADCP, seismometers, etc. 10 kW, 1 GB/s – one main electro-optical cable 50 km, AC, 1 cupper conductor + sea return ‒network active multiplexing locally (Ethernet standard) passive multiplexing based on DWDM technology – low number of channels for reliability of offshore transceiver  stability) ‒operation 10 years (some maintenance’ data transmission signal recovery by amplification

KM3NeT  2005‒2008 – design study  2008‒2012 – preparatory phase  2013‒2017 – construction definitive neutrino telescope ‒ 300 persons ‒ 200 M€

31 x 3” PMT Optical module (camera) Electronics inside

deep-sea network j+1 j optical modulator laser receiver  integrate timing system (GHz = ns)  minimise offshore electronics DWDM shore station DWDM penetrator (1) wet-matable connector (1)

6 m Mechanical cable connection Data cable storage Mechanical cable storage Frame Optical module Mechanical holder Needs new deployment technique Storey 1Digital Optical Module=Dom 2Dom’s on 1 bar=Dom-bar 20Dom-bar’s on 1 tower=Dom tower

sudden Eddie currents Temperature Earth & Sea sciences France observatory food supply Bioluminescence short lived (rare) events dominate deep-sea life permanent observatory time profile

KM3NeT  deep-sea infrastructure – 10 km 3 >100,000 PMTs, hydrophones, ACDP, seismometers, etc. <100 kW, 100 GB/s – two main electro-optical cables 100 km, DC, 1 cupper conductor + sea return ‒network ‒PON, point-to-point + amplification ‒new Ethernet standard Precision-Time-Protocol (”White Rabbit”) ‒operation 10 years without maintenance

Issues, ideas, etc.

Deep-sea infrastructure  materials – containers (glass, Ti, Al)  mechanics – drag, deployment, etc.  cables – dry versus oil-filled – little experience with vertical orientation  wet-matable connectors – expensive (combined fiber and cupper wires) – bulky (problems with handling)  penetrators – source of single-point-failures (error propagation)

data taking & processing  network – high-bandwidth & long haul integration of data transmission & timing (PTP) – (real-time) data distribution monitoring archival offline analysis (astronomy, etc.) – external triggers satellites, other infrastructures  computing – (real-time) data processing algorithms (reduction of complexity & parallelization of problem) implementation (state-of-the-art OO-programming) hardware (multi-core, GPUs)

Fiber technology  data transmission – laser/[A]PD flexible (2 x transceiver = point-to-point link) active feedback loop (intrinsically instable power, ) non-negligible electrical power consumption – modulators wavelength, phase, intensity, polarization very low power reliable – amplification long-haul communication  Energy transmission – ?  sensor – e.g. Bragg reflectrometer as deep-sea hydrophones sensitivity  low weight…