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VLVnT 09 – Vladimir Zhukov

4-th International Workshop on Very Large Volume Neutrino Telescopes for the Mediterranean Sea. LIGHT TRANSMISSION MEASUREMENTS WITH LAMS in the MEDITERRENIAN SEA. Vladimir Zhukov on behalf of the KM3NeT collaboration. VLVnT 09 – Vladimir Zhukov. Introduction.

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VLVnT 09 – Vladimir Zhukov

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  1. 4-th International Workshop on Very Large Volume Neutrino Telescopes for the Mediterranean Sea LIGHT TRANSMISSION MEASUREMENTS WITH LAMS in the MEDITERRENIAN SEA Vladimir Zhukov on behalf of the KM3NeT collaboration VLVnT 09 – Vladimir Zhukov

  2. Introduction One of the important tasks of particle physics and astrophysics in coming years is the detection of high energy cosmic neutrinos. In order to build a deep under water Cherenkov neutrino telescope  the knowledge of the water optical characteristics is mandatory. Monitoring of the water optical properties Input parameters for Monte Carlo and reconstructions Choice of the telescope site VLVnT 09 – Vladimir Zhukov

  3. Introduction Optical parameters In case of very clear Mediterranean water the optical base of the instrument should be long enough (10 and more meters) in order to minimize the errors of measurements. Since the KM3NeT is an open geometry experiment we are using non-collimated light beam to measure the transmission length Lβ = 1/β, βis the transmission coefficient. The quantity Lβcan be derived by the relation I(λ,R) = [I0(λ)/4πR2]exp[- R/Lβ(λ)] , where R is the path of light. VLVnT 09 – Vladimir Zhukov

  4. Introduction Optical parameters Measure intensity at two known distances RSand RL (indexes S and L mean “short” and “long”) the transmission length Lß can be derived by the ratio of intensities IS / IL = (RL/ RS )2 exp [(RL – RS)/Lβ] In this case we don’t care for knowledge of I0andinternal optical parameters of the instrument. NESTOR collaboration has built a transmissometer with optical base of changeable length - LAMS = Long Arm Marine Spectrophotometer Transparency of water have been investigated. Measurements have been performed in Ionian Sea in site near Pylos (April and October 2008, and May 2009) and in sites near Capo Passero (May 2009). VLVnT 09 – Vladimir Zhukov

  5. Construction of the LAMS LAMS Mechanical Structure VLVnT 09 – Vladimir Zhukov

  6. Construction of the LAMS Light Source • LED matrix, 8 groups of LEDs,  8 Wavlengths • Wavelength range 375nm – 520nm. • Each LED group turned on sequentially for 10s. • Between groups 2s off, and 14s off between rounds. • Autonomous, controlled by microcontroller. Photo-detector • Two plane HAMAMATSU S6337-01 photodiodes, • large sensitive area of 324 mm2 . • DAQ has two different channels. • Photocurrent converted to voltage & digitized. • Data taking rate ~70 Hz. • Data stored on SD memory card VLVnT 09 – Vladimir Zhukov

  7. Construction of the LAMS LAMS Lab test 1/R2-law The relation between photodiode signal and distance from light source to detector is obtained in the tests in air. IL/IS = (RS/RL)2 IL/IS = (RS/RL)2 The attenuation of intensity due to geometrical spreading of light beam follows the 1/R2 law perfectly. VLVnT 09 – Vladimir Zhukov

  8. LAMS deployments MAY 2009 NEMO (Near Capo Passero) NESTOR (Near Pylos • In May 2009 the system was deployed in sites • Site 1 near Capo Passero (36 11.019’N / 16 06.017’E), depth 3350 m • Site 2 near Capo Passero (36 11.910’N / 15 45.922’E), depth 3600 m • Site near Pylos 4.5D(36O 31.336’ N / 21O 25.635’ E), depth 4300 m VLVnT 09 – Vladimir Zhukov

  9. LAMS deployments Measurements were taken continuously during deployment with the system stationary at specific depths and during motion. The depth was determined by means of the wire length and verified by pressure meter data. The length of LAMS was changed on the deck of ship by adding or removing additional parts of the frame. R = 10 m, 15 m, 17 m and 22 m were used VLVnT 09 – Vladimir Zhukov

  10. Data analysis • A mean value of the intensity is calculated for all distances between the source and the photo-detector. • A fit to the mean values with exponential relation • provides the transmission length Lβ = 1/β, • βis the transmission coefficient. • Ris the distance between light source and detector I(λ,R) = [I0(λ)/4πR2]exp[- R/Lβ(λ)] VLVnT 09 – Vladimir Zhukov

  11. Results Measurements of the Pylos 4.5D and Capo Passero 1 Sites Site near Pylos (36o 31.336’ N / 21o 25.635’ E) Site 1 near Capo Passero (36 11.019’N / 16 06.017’E) Data from May 2009 VLVnT 09 – Vladimir Zhukov

  12. Results Measurements of the Pylos 4.5D and Capo Passero 2 Sites Site near Pylos (36o 31.336’ N / 21o 25.635’ E) Site 2 near Capo Passero (36 11.910’N / 15 45.922’E ) Data from May 2009 VLVnT 09 – Vladimir Zhukov

  13. Site 1 near Capo Passero (36 11.019’N, 16 06.017’E) Depth: 3100m (seabed: 3350m) Site 2 near Capo Passero (36 11.910’N, 15 45.922’E) Depth: 3000m (seabed: 3600m) Site near Pylos (36o 31.336’N, 21o 25.635’E) Depth: 3000m (seabed: 4300m) Transmission length at similar depths per Site Results Depth (m) 3100, Capo Passero 1 3000, Capo Passero 2 3100 3000, Pylos 4.5D Data from May 2009 VLVnT 09 – Vladimir Zhukov

  14. Site 1 near Capo Passero (36 11.019’N, 16 06.017’E) Depth: 3100m (seabed: 3350m) Site 2 near Capo Passero (36 11.910’N, 15 45.922’E) Depth: 3400m (seabed: 3600m) Site near Pylos (36o 31.336’N, 21o 25.635’E) Depth: 4100m (seabed: 4300m) Results Transmission length at deepest depth per Site Depth (m) After all this depths the telescope is located 3100, CapoPassero 1 3400, Capo Passero 2 4100, Pylos 4.5D Data from May 2009 VLVnT 09 – Vladimir Zhukov

  15. Results VLVnT 09 – Vladimir Zhukov

  16. Results Transmission length ratio (at 463 nm – near the maximum transparency) LβLβ= 1.20 Lβ Lβ = 1.14 Pylos 4,5D 4100 m Capo Pas.1 3100 m Pylos 4,5D 4100 m Capo Pas.2 3400 m (Lβ Lβ )3 = 1.73 (Lβ Lβ )3 = 1.50 Pylos 4.5D 4100 m Capo Pas.1 3100 m Pylos 4,5D 4100 m Capo Pas.2 3400 m Therefore the volume observed by one OM in the Pylos 4,5D site is larger than in the Capo Passero site. This allows one to use a smaller number of OMs for a detector built at the Pylos 4.5D site than for the same detector built in Capo Passero site for the same sensitive volume, or in other words for the same number of optical modules one can achieve a larger sensitive volume at the Pylos site than at the Capo Passero site. VLVnT 09 – Vladimir Zhukov

  17. Results Comparison with attenuation NESTOR 1992[1] LAMS 2009 Attenuation of pure water [2] Pylos 4.5 D Site Wavelength (nm) VLVnT 09 – Vladimir Zhukov

  18. Summary The water transparency in the visible region of spectrum in the various depths in the Pylos 4.5D and Capo Passero sites has been investigated with Long Arm Marine Spectrophotometer. It is established that the optical properties of both sites do not differ considerably, but for all wavelengths and on all depths water in the Pylos 4.5D site is a bit more transparent. The maximum excess is 1.2 times, and is observed for 463 nm at a depth of 3400 m. VLVnT 09 – Vladimir Zhukov

  19. BACKUP SLIDES

  20. Results Extraction of parameters Lsct and Labs *) S.A.Khanaev et al. 1992 **)M.Jonasz and G.Fournier Light Scattering by Particles in Water, Elsevier 2007 Ocean Optics. Physical Optics of Ocean. Nauka, Moscow 1983 (in Russian) VLVnT 09 – Vladimir Zhukov

  21. References S.A.Khanaev et al. Measurements of water transparency South-West of Greece. 2nd NESTOR INTERNATIONAL WORKSHOP. OCTOBER 19-21, 1992 in PYLOS-GREECE R. Smith and K. Baker. Optical properties of the clearest natural waters (200 – 800 nm) Appl.Opt. V20, N2, 1981 G.Riccobene et al. Deep sea water inherent optical properties in The Southern Ionian Sea. arXiv: astro-ph/0603701 v1 25 Mar 2006 Ocean Optics. Physical Optics of Ocean. Nauka, Moscow, 1983, pp. 225, 226, 234 (in Russian, A.S Monin editor. M.Jonasz and G.Fournier Light Scattering by Particles in Water, Elsiver 2007 VLVnT 09 – Vladimir Zhukov

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