1. Acoustic Measurements in ANTARES: Status and Aims
Robert Lahmann
University Erlangen-Nuremberg
June 28, 2006 ARENA 2006, Newcastle
Outline:
The ANTARES detector
Acoustic detection of UHE neutrinos
Acoustic detection with ANTARES
Conclusion and Outlook

2. The ANTARES Collaboration
IFIC, Valencia
University of Catania LNS Catania
University of Bari
University of Rome
University of Erlangen
ITEP Moscow
KVI Groningen
NIKHEF, Amsterdam
University of Bologna
University of Pisa
University of Genova
IFREMER, Brest
DSM/DAPNIA/CEA, Saclay
APC Paris
IPHC (IReS) Strasbourg
Univ. de H.-A., Mulhouse
CPPM, Marseille C.O.M. Marseille
LAM, Marseille
IFREMER, Toulon GeoAzur Villefranche
Cable
More than 20 Institutes from 6 European countries
ANTARES 2500m depth
aim: built and operate an neutrino telescope

3. The ANTARES Neutrino Telescope
Hostile environment:
Seafloor at 2500m depth (pressure up to 250 bar)
sea water (corrosion)
12 detection lines with
25 storeys each
Each line holds 75 PMTs

4. Basic detector element: storey
Local Control Module
(in the Ti-cylinder)
Optical Module (OM): 17” glass sphere
10” PMT

5. ANTARES: Current Status
Line 1, first complete line
in operation since 2 March 2006
Mini Instrumentation Line with Optical Modules (MILOM)
in operation since 12 April 2005
Production of remaining lines in progress
12 lines are expected to be operating by end 2007

6. ) ANTARES is a Acoustics in ANTARES
ANTARES = Astronomy with a Neutrino Telescope and Abyss environmental RESearch
) ANTARES is a
water Cherenkov neutrino telescope
and
test platform for deep-sea investigations
use the framework to evaluate the prospects of an
acoustic neutrino detector
and
test acoustic neutrino detection methods

7. Acoustic Signature of UHE Showers
Askaryan, 1979
Energy deposition
Water gets heated (nK)
expansion
pressure pulse
A.V. Butkevich et al., Phys. Part. Nuc., 29 (3), 266, 1998
Advantage: acoustic absorption length ~ km !!!

8. Acoustic Background BIP Correlated BIP rate ) main objective!
General background contributions:
inherent noise of sensor/electronics
thermal noise of water
noise from sea surface
point sources.... 2P
Important background:
Bipolar Pressure Signal
BIP
From individual hydrophones: single BIP rate;
From several hydrophones:
Correlated BIP rate ) main objective!

9. ANTARES: Setup with Acoustics
3 more Acoustic Storeys in an additional line: Plans to be finalized
Instrumentation Line with 3 Acoustic storeys
Deployment foreseen first half 2007

10. Integration of acoustics into the IL
Plan:
Install 3 acoustic storeys in the Instrumentation Line for 2007 deployment in a depth of ~2300m to ~2180m
Strategy:
Use unmodified ANTARES components (mechanical, electronic) wherever possible
Use mainly commercial parts for additional electronics, cables, connectors
(Details in the presentation of Kay Graf tomorrow)
~14.5m
~100m

11. Arrangement of Sensors
~1m : - local coincidences for suppression of uncorrelated background
hydrophones
15m to 100m : - directional reconstruction
Aim: measurement of BIP-event density
in a large volume (km3) for a long time (yr)
with a dedicated array of acoustic sensors

12. Measurements with one storey
Coincidence trigger from k out of N hydrophones:
Look for correlated signal shapes above a
threshold within a time window (T~1ms):
~1m
0 ms ms 0.2 ms 0.3 ms 0.4 ms 0.5 ms 0.6 ms 0.7 ms t [s]
Can also perform reconstruction of direction/
distance (with limited accuracy)

13. Investigations with one line
Acoustic sensors along one line: Focus on random coincidences and coherence length
How do random coincidences compare to rates from point sources at different length scales?
Coherence length: How do signal shapes correlate along a wave front?
Point sources

14. Autonomous Transponders
Position Reconstruction of Storeys
Acoustic reconstruction in ANTARES:
Transceivers:
Sender/Receiver on Bottom String Socket (BSS) of MILOM (plus Line 1 and future detection lines)
Autonomous Transponders
Benefit for acoustic detection:
As for optical track reconstruction: know position of acoustic storeys to better than 10 cm
Transmitters can be used for calibration
MILOM
BSS
226m
175m
Autonomous Transponders
In addition: orientation of each storey has to be reconstructed:
Compass, tiltmeter in every storey (inside electronics container)

15. Setup of a 3D-array 1km3 volume
MC-Investigations by T. Karg (Ph.D. thesis & ARENA05):
Number of “Acoustic Clusters” (ACs, e.g. ANTARES acoustic storeys) in a 1km3 cube
400 AC
200 AC
50 AC
10 AC
800 AC
1km3 volume
Sensor threshold 5mPa (SS0: RMS ~2.5mPa integrated from 1kHz to 100kHz): No significant change above 200 AMs/km3

16. BIP - Measurements ~200m ~115m
200 ACs/km3 corresponds to inter-AC distance of ~170m
→ excellent opportunity for realistic 3-dim reconstruction with ANTARES when a second line is equipped with acoustic sensors:
~200m
~115m

17. Conclusions and Outlook
Currently two lines in operation at ANTARES site
The ANTARES detector poses an excellent opportunity to study acoustic detection methods
First acoustic components for investigation of acoustic background to be installed in first half of 2007
All 12 detection lines expected to be deployed and connected by end 2007
Acoustic equipment on an additional line foreseen