Acoustic Calibration for the KM3NeT Pre-Production Module

Acoustic Calibration for the KM3NeT Pre-Production Module

Alexander Enzenhöfer on behalf of the KM3NeT consortiumVLVnT 2011Erlangen, 12.10. – 14.10.2011

Why and how to do acoustic calibration

2Alexander Enzenhöfer, VLVnT 2011, 12.10.2011

Why acoustic calibration?

• Deep sea as highly dynamic environment:• Variable sea current, in both speed and direction

• Need to know PMT-positions with ~20 cm precision

• Necessity for calibration signals with acceptable attenuation in water (only ~100 m for light, ~1 km for sound)

• Low cost with possibility to use commercial systems


Requirements for used devices

• Withstand high ambient pressure• Capability to detect small signal amplitudes• Sea water durability• Simplicity• Reliability• High duty cycle


Acoustic calibration principle

• Usage of dedicated emitters and receivers• Emitters at fixed positions on the sea floor• Receivers attached to detection units

• Based on the piezoelectric effect• Different signals (frequency, length or

shape) to distinguish between different emitters

• Triangulation of the detection units using signal arrival times and known emitter positions


Variety of different devices

• Commercial devices(cf. talk ID 91 afterwards)

• Custom-built devices(AMADEUS/ANTARES, NEMO(cf. talk ID 60 before))

Various geometries,

frequency ranges, …


Our concept: Further development of Acoustic Modules in ANTARES


Acoustic Module in ANTARES• Developed at the ECAP• 3 Acoustic Modules integrated in AMADEUS• Acoustic sensor glued to the inside of

pressure resistant housing• Acoustic sensor protected against

environmental influences• No additional feedthrough• Show good results for storey

positioning


Measurement of Heading with Acoustic Modules

Fit known positions of sensors in coordinate system of the storey to the reconstructed positions


Positioning option for KM3NeT

Potential of acoustic sensors:• Positioning• Investigation of acoustic neutrino detection

techniques• Marine science

Acoustic Modules (AMs) allow for anintegration of acoustic sensors into Optical

Modules

Feasibility for KM3Net has to be tested PPM


Concept of a combined Opto-Acoustical Module

Optical Module:

• PMT(s) integrated into pressure resistant housing

Acoustic Module:

• Acoustic sensors integrated into pressure resistant housing

Opto-Acoustical Module(OAM):

• PMT and acoustic sensor integrated into pressure resistant housing


Possible disadvantage resulting from combination• Design dependent angular acceptance

• Electronic interference• Module power supply (supply/generation of different voltages

inside the module)• PMT HV supply• PMT operation and piezo operation

• Interface water-glas-piezo• Complex signal path through the glass sphere• Coupling of the piezo to the glass


First results (old design)

Integrated PMT influence RMSnoise ≈ 5 x RMStyp. sea-state


Recorded noise spectra (sensor totally unshielded)

Acoustic sensor – new prototype

• New design:• Compact• Better shielding• Different amplifier layout


Cooperation in the context of KM3NeT activities


Cooperation with LNS-INFN Catania

Integration of acoustic sensorsinside single PMT optical module


Results using NEMO Phase II infrastructure

Noise spectrum without PMT(ECAP sensor (top),NEMO hydrophone (bottom))

Noise spectrum with powered PMT(ECAP sensor (top),NEMO hydrophone (bottom))


Cooperation for KM3NeT PPM

Integration of acoustic sensor inside multi PMToptical module (Digital Optical Module)


PPM - DAQ

Alexander Enzenhöfer, VLVnT 2011, 12.10.2011 19

PMT - Data

to coastFPGA

Hydrophone

Acoustic sensor

Main amplifier board

ADC board designed by INFN Catania(commercial stereo ADC, 24 bits @ 192 kSps)

ADC

Summary

• Different possibilities to realise acoustic calibration

• PPM allows for detailed studies on different devices under real conditions

• ECAP sensor concept shows good results in the laboratory and more sophisticated measurements are planned


Acoustic Calibration for the KM3NeT Pre-Production Module

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