Deep Sea Acoustic Neutrino Detection and the AMADEUS System as a Multi-Purpose Acoustic Array

1. Robert Lahmann VLVnT – Toulon – 24-April-2008 Deep Sea Acoustic Neutrino Detection and the AMADEUS System as a Multi-Purpose Acoustic Array

2. Outline • Why acoustic neutrino detection and how does it work? • The acoustic detection test system of ANTARES (AMADEUS) • First results from AMADEUS • Conclusions

3. Motivation for Acoustic Neutrino Detection OpticalCherenkov Alternative methods High energies: Huge volumes (>10km3) required  new detection methods

4. Cosmic Rays in the Ultra High Energy Region Auger Observation of suppression in cosmic ray flux at E1019.5 eV From arxiv/0712.3727v1 (Auger Coll.)

5.  Temperature hadronic cascade ≈10m Time ≈1km Acoustic Signals from Neutrinos Instantaneous heating, followed by slow cooling Ecasc= 1 EeV @ 1km Adapted from arxiv/0704.1025v1 (Acorne Coll.)

6. Acoustic Background in the Sea • Detection threshold depends on details of background;expect E > 1018 eV (1 EeV)

7. Acoustic Detection in Water/Ice • ACoRNE(Acoustic Cosmic Ray Neutrino Experiment)Uses military hydrophone array near coast of Scotland (8 hydrophones) • Lake Baikal • OnDE (Ocean noise Detection Experiment) • 4 hydrophones at NEMO site • SAUND (Study of Acoustic Ultra-high Energy Neutrino Detection)Uses military hydrophone array near Bahamas SAUND I : 7 hydrophonesSAUND II (since 2006) : 49 hydrophones • SPATS (South Pole Acoustic Test Setup) • AMADEUS

8. ANTARES Modules for the Acoustic Detection Under the Sea (AMADEUS) • ANTARES: • 12 detection lines • 1 Instrumentation Line (IL07) for environmental monitoring • Acoustics in ANTARES: AMADEUS • 6 storeys with a total of 36 sensors • Spacings between sensors from 1m to 340m • Status of acoustics on IL07: • Continuous data taking since 5-Dec-2007 • 17 of 18 hydrophones working

9. Goals and Features of the AMADEUS Project • Goals : • Feasibility study for future large scale acoustic detector • Background investigations (rate of neutrino-like signals, localisation of sources) • Investigation of signal correlations on different length scales • Development and tests of filter and reconstruction algorithms • Studies of hybrid detection methods • Features: • Combines local clusters of acoustic sensors with large cluster spacing • All data to shore, but off-shore pre-trigger possible • triggered data (on-shore) ~3 GByte/day • continuous data taking with ~90% on-time • Full detection capabilities (time synchronisation, DAQ,…)

10. ~10cm Setup of Acoustic Storey with Hydrophones Hydrophone:Piezo sensorwith pre-amplifierand band pass filter in PU coating Titanium cylinderwith electronics 3 custom designed Acoustic ADC boards

11. Characteristics of the Acoustic System Hydrophones • Commercial and self-made types used • Typical sensitivity of -145 dB re. 1V/μPa 3 Acoustic ADC boards • 16 bit digitisation • Bandwidth up to ~125 kHz • Adjustable digitisation rate, max. 500 kSamples/s • System extremely flexible due to use of FPGA off-shore (“downsampling”, adjustable gain 1 to 562, off-shore firmware updates possible)

12. Power Spectral Density of Background Noise preliminary Observed background noise in deep sea basically as expected

13. Pinger of ANTARES Positioning System (I) Pinger of ANTARESpositioning systemare also used for positioning of acoustic storeys(work in progress)

14. Pinger of ANTARES Positioning System (II) • Pinger signal: • Amplitude reduced with distance • Temporal structure (1st and 2nd ping originate from different positions)

15. Localisation of Transient Signals Reconstruction of sourcedistance with triangulationfrom several storeys Most probabledirection of source

16. Correlation with Weather Conditions preliminary Weather conditions measured at Hyères airport, about 30km north of ANTARES site • Correlation coefficient ~ 80% • Deep-sea noise dominated by sea surface agitation

17. ANTARESglass sphere 17" (42cm) Piezo sensors + preamplifiers Acoustic Modules One of the 3 acoustics storeys on line 12 will consist of “Acoustic Modules” Design allows for integration of acoustic sensors into pressure housing of photo sensors  No need for additional mechanical structures

18. Conclusions • Acoustic detection is a promising option for neutrino detection at ultra high energies • The AMADEUS system has all features required for an acoustic neutrino telescope (except size) • Can be used as a multi purpose device (neutrino detection, positioning, marine research) • “Acoustic Modules” are an option for acoustic measurements without additional mechanical structures

19. Backup Transparancies

20. Acoustic Storeys on the IL07 Deployment July 2007 Storey 2 (6 commercial sensors) Storey 3 (6 sensors produced at Erlangen) Storey 6 (6 commercial sensors)

21. Distribution of Amplitudes from Hydrophones Commercial Hydrophones Hydrophones produced at Erlangen

22. Correlation with weather conditions Weather conditions measured at Hyères airport, about 30km north of ANTARES site

23. = volume expansion coefficient = specific heat capacity (at constant pressure) = speed of sound in water ( ~1500 m/s) Temperature Time Resulting pressure pulse with 2P Dt Acoustic Signals from Neutrinos p = pressure  = energy density Instantaneous heating, followed by slow cooling