1 / 29

IFIC - Instituto de Física Corpuscular (CSIC - UV) VALENCIA, SPAIN

WATER ABSORPTION LENGTH MEASUREMENT WITH THE ANTARES OPTICAL BEACON SYSTEM. HAROLD YEPES. IFIC - Instituto de Física Corpuscular (CSIC - UV) VALENCIA, SPAIN On behalf of the ANTARES collaboration. International Workshop on Very Large Volume Neutrino Telescopes.

liz
Download Presentation

IFIC - Instituto de Física Corpuscular (CSIC - UV) VALENCIA, SPAIN

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. WATER ABSORPTION LENGTH MEASUREMENT WITH THE ANTARES OPTICAL BEACON SYSTEM HAROLD YEPES IFIC - Instituto de Física Corpuscular (CSIC - UV) VALENCIA, SPAIN On behalf of the ANTAREScollaboration International Workshop on Very Large Volume Neutrino Telescopes 13 – 15 October 2009, Athens, Greece

  2. 1.2 TeV Muon crossing the detector (SIMULATION) OUTLINE • THE ANTARES NEUTRINO TELESCOPE • THE ANTARES OPTICAL BEACON SYSTEM • EXPERIMENTAL PROCEDURE • PROPAGATION OF PHOTONS AND MC SIMULATIONS • PRELIMINARY RESULTS • CONCLUSIONS International Workshop on Very Large Volume Neutrino Telescopes 13 – 15 October 2009, Athens, Greece

  3. THE ANTARES NEUTRINO TELESCOPE • University of Erlangen • Bamberg Observatory • ITEP, Moscow • Moscow State Univ • NIKHEF (Amsterdam) • KVI (Groningen) • NIOZ Texel International Workshop on Very Large Volume Neutrino Telescopes • CPPM, Marseille • DSM/IRFU/CEA, Saclay • APC, Paris • LPC, Clermont-Ferrand • IPHC (IReS), Strasbourg • Univ. de H.-A., Mulhouse • IFREMER, Toulon/Brest • C.O.M. Marseille • LAM, Marseille • GeoAzur Villefranche • University/INFN of Bari • University/INFN of Bologna • University/INFN of Catania • LNS – Catania • University/INFN of Pisa • University/INFN of Rome • University/INFN of Genova • IFIC, Valencia • UPV, Valencia • UPC, Barcelona • ISS, Bucarest 7 COUNTRIES 28 INSTITUTES ~ 150 SCIENTISTS AND ENGINEERS 3 13 – 15 October 2009, Athens, Greece

  4. nm m PMT array W N X p Cherenkov light from µ 42°  Seabed m nm Interaction atm p  THE ANTARES NEUTRINO TELESCOPE Neutrinos can interact with the surrounding of the detector. Main detection channel: nm interaction giving an ultra-relativistic m inducing Cherenkov light in a cone (ne and nt can also be detected). International Workshop on Very Large Volume Neutrino Telescopes • Two kinds of background at the ANTARES site: • Physical Background : Cosmic Rays interactions (atmospheric m and n). • Optical Background: Bioluminescence and 40K decay (sea environment). 4 13 – 15 October 2009, Athens, Greece

  5. Horizontal layout 14.5 m 45° Storey Junction box 100 m Link cables 2500 m depth ~60 m THE ANTARES NEUTRINO TELESCOPE International Workshop on Very Large Volume Neutrino Telescopes • 3D array of ~900 PMT. • 12 detection lines. • 25 storeys / line. • 3 PMTs / storey (detection units). • 40 km off Toulon coast (France). 5 13 – 15 October 2009, Athens, Greece

  6. 60 m LED andLASERfast and controlled sources of pulsed light with a well-known emission time. 60 m The main goal is to perform an in-situ timing calibration, moreover they can be used to studywater optical properties. 300 m 300 m LED Beacon: Floors 2, 9, 15, 21 LASER Beacon: Lines 7, 8 THE ANTARES OPTICAL BEACON SYSTEM F21 F15 International Workshop on Very Large Volume Neutrino Telescopes F9 F2 6 13 – 15 October 2009, Athens, Greece

  7. Energy per pulse at maximum (DC level, 24 V) ~ 150 pJ (wavelength 472 nm). Internal PMT Hamamatsu H6780-03 (rise time ~ 0.8 ns) to know the emission time of the light pulse. A variable capacitor to synchronise (~200 ps) the emission time of the 36 LEDs. TOP LED THE ANTARES OPTICAL BEACON SYSTEM The LED Beacon International Workshop on Very Large Volume Neutrino Telescopes 7 13 – 15 October 2009, Athens, Greece

  8. Energy per pulse ~ 1.0 mJ (wavelength 532 nm). Variable light intensity (crystal liquid attenuator system). Internal fast photodiode to know the time emission of the light pulse. THE ANTARES OPTICAL BEACON SYSTEM The LASER Beacon International Workshop on Very Large Volume Neutrino Telescopes 8 13 – 15 October 2009, Athens, Greece

  9. Rmin Rmax ¡ PRELIMINARY! F2 EXPERIMENTAL PROCEDURE Skip all points at R < Rmin to avoid the electronic dead time effects Skip all points at R > Rmax to avoid fake signals due to noise fluctuations Isotropic source of photons, the photon field measured by a PMT at a distance R is: Plot the charge (Q) collected as a function of the distance (R) International Workshop on Very Large Volume Neutrino Telescopes Measure amount of light collected by OMs of the upper storeys in the same line One single LED of the top group of the lowest LED Beacon in the line (F2) flashes 9 13 – 15 October 2009, Athens, Greece

  10. Qsignal Tmax Qnoise Tmin EXPERIMENTAL PROCEDURE TIME DISTRIBUTION FOR SELECTED HITS Determine the peak  Gaussian fit Choose fixed time window [Tmin,Tmax] and select the hits in this time window. Tmin= Tpeak – 3s. Tmax= Tpeak + 1000 ns. Calculate their overall charge Qtot. International Workshop on Very Large Volume Neutrino Telescopes 10 13 – 15 October 2009, Athens, Greece

  11. NOISE LEVEL EXPERIMENTAL PROCEDURE NOISE CONTRIBUTION FOR SELECTED HITS • Substract the noise contribution • (Qsignal = Qtot - Qnoise) • Fit a constant in the • [-1000, -50] ns range: • Background Level (B) • Qnoise = B*(Tmin - Tmax) International Workshop on Very Large Volume Neutrino Telescopes 11 13 – 15 October 2009, Athens, Greece

  12. EXPERIMENTAL PROCEDURE CHARGE LOSSES Some hits get lost due to the electronic dead time from the readout of the two electronic cards (ARSs) of the PMT. Electronics dead time effects related to Rminto fit. Consider only the region where the probability to get more than one photoelectron is negligible (i.e. < 1 %): International Workshop on Very Large Volume Neutrino Telescopes 12 13 – 15 October 2009, Athens, Greece

  13. CORRECTED BY EFFICIENCY EXPERIMENTAL PROCEDURE PMT RELATIVE EFFICIENCY CORRECTION • PMTs don’t have the same efficiency (ePMT): • Assume that the Qnoise ~ ePMT. • Normalize PMTs signal charge to their own noise charge: International Workshop on Very Large Volume Neutrino Telescopes 13 13 – 15 October 2009, Athens, Greece

  14. EXPERIMENTAL PROCEDURE NOISE FLUCTUATIONS At large distances the signal can be confused with noise fluctuations. Consider only points with: The maximum distance Rmax to fit is related with the noise fluctuations at higher distances. International Workshop on Very Large Volume Neutrino Telescopes NOISE 14 13 – 15 October 2009, Athens, Greece

  15. Attenuation Length Collimated beam Effective Attenuation Length Isotropic source PROPAGATION OF PHOTONS IN DEEP SEA WATER Absorption length Scattering Length Scattering phase function (b) • Scattering angle • distribution • Molecular scattering (Rayleigh)  Isotropic • Particle scattering (Mie) •  Strong forward peaked International Workshop on Very Large Volume Neutrino Telescopes 15 13 – 15 October 2009, Athens, Greece

  16. PROPAGATION OF PHOTONS IN DEEP SEA WATER Morel and Loisel approach Scattering phase function Particle scattering (Petzold’s values) (strong forward peaked) <cosq>=0.924 Molecular scattering (isotropic) <cosq>=0 International Workshop on Very Large Volume Neutrino Telescopes Average cosine of global distribution Probability of molecular scattering (Rayleigh) 16 13 – 15 October 2009, Athens, Greece

  17. WHAT ARE WE MEASURING? Special simulation code for timing calibration with Optical Beacons. L  Convolution of optical properties. MC Tools to clarify what parameter is. • MAIN FEATURES • Width of the light pulse. • Light absorption in water simulated. • Light scattering in water simulated. • PMT response simulated (KM3 parametrisation for 10’’ Hamamatsu PMTs). • Gain fluctuations simulated. • TTS of PMTs simulated. CALIBOB MC SIMULATIONS MC TOOLS SIMULATION International Workshop on Very Large Volume Neutrino Telescopes 17 13 – 15 October 2009, Athens, Greece

  18. MC SIMULATIONS MC PRODUCTION Water model: labs = 60 m fixed h = 0.17, 0.05 lscat = 30, 40, 50, 60, 70 m labs = 60 m labs = 60 m International Workshop on Very Large Volume Neutrino Telescopes • L depends strongly on the scattering and time integration gate for selected hits. Tmax↓ L → latt Tmax ↑ L → labs 18 13 – 15 October 2009, Athens, Greece

  19. labs = 60 m latt lsca MC SIMULATIONS MC PRODUCTION: Tmax = 1000 ns fixed. labs = 60 m fixed η = 0.17, 0.15, 0.12, 0.10, 0.05 • For all the lscat – η couples considered: latt < L < labs • Depending on scattering: labs – L ≈ 5 - 10 m • (h ↓ + lscat↑) L → labs • (h↑ + lscat ↓) L → latt International Workshop on Very Large Volume Neutrino Telescopes L1000 IS A LOWER LIMIT FOR THE labs 19 13 – 15 October 2009, Athens, Greece

  20. Rmin Rmin ¡PRELIMINARY! ¡PRELIMINARY! Rmax Rmax PRELIMINARY RESULTS SYSTEMATIC EFFECTS ARE NOT YET FULLY UNDERSTOOD SOME FIT EXAMPLES International Workshop on Very Large Volume Neutrino Telescopes • Preliminary results indicate labs ~ 60 m or greater in agreement with MC muon track reconstruction. • Take more special RUNs to check the reproducibility of the results. • Still more work on systematics. 20 13 – 15 October 2009, Athens, Greece

  21. LED CB 30 (470 nm) PRELIMINARY RESULTS FUTURE PLANS One different wavelength on each face. Three LEDs per face pointing up-wards. To assure redundance and to check systematics. International Workshop on Very Large Volume Neutrino Telescopes Rise Time ~ 2.5 ns FWHM ~ 5 ns Flashing at 300 Hz Voltage at 23 Volts 21 13 – 15 October 2009, Athens, Greece

  22. Mean Mean FWHM FWHM 442 477 365 405 l [nm] l [nm] LED HLMP-CB30-K000 LED VAOL-5GUV8T4 PRELIMINARY RESULTS International Workshop on Very Large Volume Neutrino Telescopes 22 13 – 15 October 2009, Athens, Greece

  23. The ANTARES Optical Beacon system has been designed for timing calibration, but it can be also used to study of water optical properties. • An experimental procedure to measure the absorption length has been developed based on the exponential fit to the collected charge by the PMTs and the arrival time distributions. • MC simulations confirm the difficulty to disentangle the optical parameters from the measured value. The higher the integration gate when measuring L, the closer L is to the absorption length. • Systematics effects still not fully understood but work is in progress. • First measurements indicate that L ~ 57 m < labs. More data RUNs needed to check this result. • A modified version of the Optical Beacon to measure the absorption length at different wavelengths will be ready soon for integration and deployment on the ANTARES detector. CONCLUSIONS International Workshop on Very Large Volume Neutrino Telescopes 13 – 15 October 2009, Athens, Greece

  24. BACKUP SLIDES International Workshop on Very Large Volume Neutrino Telescopes 13 – 15 October 2009, Athens, Greece

  25. LINE F21 e- (bdecay) 40K F15 40Ca γ F9 Bioluminescence Median rate from 03/06 – until 05/08 F2 OPTICAL BACKGROUND IN THE ANTARES SITE • Muon: • 2 ms m crossing the detector. • Bioluminescence: • Continuous background ~ 30 kHz over 10” PMT and 0.3 p.e threshold. Sudden bursts ~ MHz. • 40K Decay: • Continuous background ~ 30 kHz over 10” PMT and 0.3 p.e threshold. International Workshop on Very Large Volume Neutrino Telescopes 13 – 15 October 2009, Athens, Greece

  26. MC SIMULATIONS WATER MODELS • Two water models available: • Medsea. • Partic. • Both models use Kopelevich’s parameterization of scattering length, but with different parameters, and the same parameterization of absorption length. • The two models differ also for the parameterization of scattering angle: • Medsea  Two Henyey-Greenstein phase functions . • Partic  Rayleigh scattering + water particle diffusions. International Workshop on Very Large Volume Neutrino Telescopes 13 – 15 October 2009, Athens, Greece

  27. MAIN PARAMETERS IN DATA ANALYSIS PHOTOELECTRON REGION NOISE FLUCTUATIONS The number n of hits collected on the OM follow the Poissonian statistics: The probability to get more than one hit in the same flash is: To avoid charge losses, consider only the region where this probability is negligible (i.e < 1 %): The number of signal hits at closest useful distance Rmin is This number decreases quickly as the distance R grows Increase the number of flashes Nflashes Limited by the maximum DAQ rate of 300 Hz International Workshop on Very Large Volume Neutrino Telescopes 13 – 15 October 2009, Athens, Greece

  28. ¡ VERY PRELIMINARY ! ¡ VERY PRELIMINARY! Rmin ~ 130 m Rmax ~ 300 m ¡ VERY PRELIMINARY ! Rmin ~ 145 m Rmax ~ 300 m RESULTS Rmin FOR HIGH INTENSITY RUNS (Tmax = 1000 ns) International Workshop on Very Large Volume Neutrino Telescopes Rmin is not the same for high intensity RUNs. For m = 0.20, Rmin changes (1 floor aprox -> 15 m). 13 – 15 October 2009, Athens, Greece

  29. RESULTS Effect of the Voltage on the wavelength International Workshop on Very Large Volume Neutrino Telescopes LED – 385 nm LED – 505 nm 13 – 15 October 2009, Athens, Greece

More Related