NESTOR – a status report

1. Neutrino Extended Submarine Telescope with Oceanographic Research NESTOR – a status report Presented by Petros A. Rapidis National Center foir Scientific Research “Demokritos” Athens, Greece On behalf of the NESTOR collaboration Describing the work of many, and also the work of others Presented on April 22, 2008 at the 3rd Workshop on Very Large Volume Neutrino Telescopes (VLVnT08),at Toulon, France, April 22-24, 2008

2. University of HamburgUniversity of Kiel Germany University of Athens National Observatory of Athens – NESTOR Institute for Deep Sea Research, Technology and Neutrino Astroparticle Physics University of CreteNCSR “Demokritos” Hellenic Open University  Aristotelian University of ThessalonikiUniversity of Patras University of Thessaloniki Greece Russia Bureau of Oceanological Engineering  & Institute For Nuclear Research, Russian Academy of Sciences Sholokov Open University University of Bern CERN Switzerland University of HawaiiLawrence Berkeley National Laboratory U.S.A.

3. Outline: • A description of the NESTOR project • A few words about the 2003 run • and what we learned from this • Plans for the future : • The NuBE proposal • Site studies • Deployment work

4. The area off the coast of the Southern Peloponnese easternmost and deepest of the three areas under consideration 2400m 4500 m - 5100 m 3500m Toulon Capo Passero Pylos

5. Also a very versatile and convenient area s

6. NESTOR TOWER 32 m diameter 30 m between floors 144 PMTs Energy threshold as low as 4 GeV 20 000 m2 Effective Area for E>10TeV

7. ~4,000m from the surface  ~400m Original ideas about a NESTOR full detector Driven by the assumption that one has to minimize the wet-mateable connections

8. Hamamatsu PMT R2018-03 (15”) • Benthos spheres • μ-metal cage • power supply The 2003-Detector

10. The Cable Deployment: June 2000 ElectroOptical cable to shore(18 fibers +1 conductor) Deployed in June 2000 by the cableship MAERSK-FIGHTER (ALCATEL- TELEDANMARK) Cable was damaged during laying because of ship’s problems. Cable landing has been completed and first three km have been buried 2 m inside the bottom sand. NESTOR Star Deployment (March 2003)

12. Coincidence rate for OMs as measured at a depth of 3800m with 1pe thresholds The points represent the data, the solid line the Monte Carlo estimation including background and the dashed line the Monte Carlo estimation for the contribution of the atmospheric muons. 4 fold rate is 0.25 Hz for this 12 PMT node.

13. K40 Background:A stable calibration source Calibration Data from a depth of 3800 m PMT Pulse Height Distribution single p.e. LED Run single p.e. pulse height distribution two p.e.s pulse height distribution dark current pulse height distribution sum of the above

14. Event 1785 – Run 81 – BFile 3 c

15. Event 1785 – Run 81 – BFile 3 c

16. The measured vertical muon intensity I0 and the index a, at a depth of 3800 m water equivalent, are

18. Looking to the future…. What can we do before the big one comes in ?!

20. Triggering Digitization Event Formatting Controls Slow Controls Calibration Unit Shore Laboratory Signal transmission & Control Power supply PMT signal transmission low voltage supply (24V) control and monitoring signal transmission Theodore Athanassopoulos’ anti-talk Ti-Sphere Electronics

21. NuBE - NESTOR

22. …meanwhile … a • a GRB duration is of the order of 100 seconds

23. Neutrino Burst Experiment – a quick look for AGN – very high energy neutrino coincidences 300 m

24. Two cluster NODE

25. This drawing is to scale

26. Some simple considerations : Cherenkov light produced for 1 cm in water is ~200 photons in the 350-550 nm range Let us consider the case of a 100 TeV m ( 1014 eV) Range in water (km) = 4.0 x ln (1+E(TeV)) (i.e. 10 TeV ~ 9 km, 100 TeV ~ 18 km ) Thus a m on the average is accompanied by a ‘bundle’ of particles - 100 TeV / (18 km x 1 MeV/cm) ~ 60 particles (assuming they are minimum ionizing and have a de/dx of 1 ~MeV/cm) (n.b. a better simulation gives 77 particles) In passing: a 100 TeV electron (e.g. from from NC interaction, and given Xrad = 36 cm) will give rise to a dense shower with a length of L ~ 10 m , i.e. ~40 000 particles. Also a t is quite similar to an electron or muon The Optical Module is a 37 cm diameter sphere. In a 37 cm length with 200 ph/cm there will be ~ 10^4 photons produced by a 100 TeV m Light at a node 300 m away –Project to a cylinder A=2p R(300m)L(37cm) ~ 6x106 cm2 Thus we have 0.0015 photons/cm2 and for a 15" PMT of cathode area of 1080 cm2 We expect 1.5 photoelectrons. Now let us use a quantum efficiency of 20% and an overall efficiency for transmission losses, reflections in the glass etc. of 50% and take into account that the node has 16 OM’s  2.4 photoelectrons per node, i.e. can be seen !

27. At 100 TeV neutrinos begin to be absorbed by the earth, thus one has to start looking up. So the crucial question is : can you handle the flux of downgoing cosmic ray induced muons ? As shown earlier at a depth of 4 km with the floor of NESTOR (12 OM) the 4-fold rate is .25 Hz for downgoing m. Thus for a 16 OM node it is ~1 Hz. For an active window of 3 ms rate 1Hz x 1Hz x 3x10-6 s = 3x10-6 s-1 or 3x10-4 in 100s GRB are ~300 per year = 10-5 s-1 or 10-3 in 100 s So for a 100 s window fake is 3x10-4 x 10-3 = 10-7 in a year long run is the fake rate.

28. 2 node trigger with E>65 GeV for m passing between stings nodes Waxman paper says that there should be 10-100 nm of 1014 eV per GRB for 1km2 So we can hope for 5-50 of such events per year (or more if the situation is more favorable).

29. Continuation of Site Studies Light Absorption Measuring System To study sedimentation – fouling … Autonomous – complements sediment trap studies. Summary of sediment trap studies

30. Bioluminescence work See J. Graig’s talk tomorrow 0 5000

31. Extensive measurements of deep sea currents Pylos 4500 m deep site The deep currents have very low velocities that rarely exceed 6 cm/s. In general, the flow at the Pylos site of 4500 m depth is northward and 90% of the time is below 4 cm/s, and at the 5200 m deep site is southward but substantially weaker, with 95% of the time the current speed being below the instrument’s measurement threshold Pylos 5200 m deep site

32. Light transmission in the water Is there a significant l dependence ? Published data for ‘pure’ water … Older measurements (See Uli’s talk) 1 .01 Absorption Coefficient (m-1) For l = 460 nm .01 .004 l=300nm l=700nm

33. The talk that was not meant to be …. • Psallidas , NESTOR • Light Intensity Measuring System • ● 2 Sources: 8 LEDs in 2 groups • 1. 375nm, 420nm, 450nm, 495nm • 2. 383nm, 400nm, 470nm, 525nm • ● Detector: 2 Photodiodes • Area: 18 mm x18 mm • Type: Hamamatsu S633701 • ● Distances between source and • detector: 10 m, 15 m, 17 m, 22 m. • Data just on board of the RV Aegeon ! • Looks good ! But not fully digested yet ….

34. The Delta-Bereniki deployment platform A versatile dedicated vessel Under reconstruction – engines are mounted and she will be re-floated soon. (In a month ?)

35. Was built to allow assembly of towers - but she is a lot more versatile.

36. Heave compensated crane bridge. She will be able to hold position and allow work up to the end of Beaufort scale 4 sea (frequent white horses, 30 km/hour wind, 1 m waves)

37. Unpaid Advertisement • Belias – Proposal for a reconfigurable data acquisition system for KM3NeT • (09:30 ENG) • M. Stavrianakou - First ideas for KM3NeT on-shore data storage and distribution • (12:50 PHYS) • S. Koutsoukos – NuBE Calibration from 10s to 100s of meters in an underwater • neutrino telescope • (15:45 ENG) • T. Athanassopoulos – Commodity , FPGA based front end electronics for an • underwater neutrino telescope • (09:10 ENG) • ----------------- • A. Psallidas - Very recent measurements of light transmission in sea water • in the Pylos area And the talk that was not meant to be ….