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

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

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

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.)

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

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

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 hydrophones SAUND II (since 2006) : 49 hydrophones SPATS (South Pole Acoustic Test Setup) AMADEUS

ANTARES Modules for the Acoustic Detection Under the Sea (AMADEUS) 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

Goals and Features of the AMADEUS Project 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,…)

Setup of Acoustic Storey with Hydrophones Hydrophone: Piezo sensor with pre-amplifier and band pass filter in PU coating ~10cm Titanium cylinder with electronics 3 custom designed Acoustic ADC boards

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)

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

Pinger of ANTARES Positioning System (I) Pinger of ANTARES positioning system are also used for positioning of acoustic storeys (work in progress)

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

Localisation of Transient Signals Reconstruction of source distance with triangulation from several storeys Most probable direction of source

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

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

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

Backup Transparancies

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)

Distribution of Amplitudes from Hydrophones Commercial Hydrophones Hydrophones produced at Erlangen

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

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