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Omar Veledar ACoRNE collaboration – University of Sheffield Sapienza Universitá Di Roma 25 – 27 June 2008. Hydrophone based calibrator for seawater acoustic detection of UHE neutrinos. Outline. Rona array DAQ Calibration Pinger development Deployment Future work. Rona hydrophone array. - PowerPoint PPT Presentation
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Hydrophone based calibrator for seawater acoustic detection of
UHE neutrinos
Omar VeledarACoRNE collaboration – University of Sheffield
Sapienza Universitá Di Roma25 – 27 June 2008
Outline
Rona array DAQ Calibration Pinger development Deployment Future work
Rona hydrophone array
• North-West Scotland (ranging hydrophones)• Good test bed for future deep sea experiments
• Existing infrastructure √• Wideband hydrophones √• Omnidirectionality √• Unfiltered data √• All data to shore √• Control over DAQ √• No remote access X
Rona hydrophone array
8 hydrophones Low noise preamplifiers 1200m x 200m at mid
depth in 230m deep sea Hydrophone positioning
off during data readout
DAQ
Offshore acquisition of amplified unfiltered data (16bit ADC@140kHz, ±1.2 V, 1bit = 38.147μV = 3662.1μPa)
FLAC lossless compression (>50%)
8TB RAID interfacing to
16 tape autoloader LT03
tape robot (possible to
relocate) Offline signal processing
and analysis - unlimited data re-processing
Quantum Superloader 3
Calibration - hydrophone
Acoustic detection of UHE neutrinos relies on ability to calibrate hydrophones - bipolar acoustic pulse from single omnidirectional source
Thermal energy resembling (shape and intensity) that of a neutrino induced shower should be deposited: array - interface pattern analogous to neutrino generated ‘pancake’
Other possibilities: Laser – interesting, but impractical Copper plate current discharge
Calibrator development - progressionLaboratory tank
Swimming pool
Lake (Kelk)
Open sea (Rona)
Development
Calibrator development - toolsTx – omnidirectional ± 1.8dB @ 10kHz Rx - flat frequency response
Know system and desired output to deduce required excitation pulse
Convolution integral (t)y(t) = x(t) * h(t) - complicatedConvolution (s) - freq. domain
Y(s) = X(s) . H(s)
Inverse FFTy(t) = IFFT(Y(s))
Impulse response not practical use step response
Step response = time integral of impulse response
Signal generation - system
i
invixnvnx ][][][*][
dtgftgtf )()()(*)(
0,00,
)(xx
x
(hydrophone)input output
system & output => excitation pulse
Time domain
Discrete time signal
Impulse
xdttxH )()(
Step
Signal generation - signal
d / dtstepHydro
system H(t) o/pImp. resp.
Deconvolute i/p from sys. & o/pX(s) = Y(s) / H(s)
Transform to time domainx(t) = IFFT(X(s))
RECIPE Find step response (of the transmit hydrophone) Generate system TF (model transmit hydrophone) Find excitation signal by deconvoluting required o/p and system TF
Pool – hydrophone modelling
Hydrophone step response is recorded at various distances and dejittered
Hydrophone data fitting
5th order TF used to model hydrophone
TF:Mathematical representation of the relationship between the i/p and o/p of a LTI system
Technique verification
Excitation signal
Desired acoustic pulse and the estimated hydrophone driving electrical signal
Generates10 Pa @ 1m
Pool - bipolar acoustic pulse
Measured at various distances
Rona - field trip
The joys of British “Summer”
Future work
Repeat Rona deployment at different sea state and over different hydrophones using new excitation pulses
An array development using 8 hydrophones Line array – acoustic pancake
Fully autonomous for great depths Surface deployment => Power Amplifier, easy DAQ,
(linearity?) Field data analysis
New excitation signal
Restrictive by the hydrophone linearitypotentially, can generate up to
approximately 60 Pa @ 1m
See Bevan et al. – parameterisation:more energy at core of the shower
Array hydrophone count2 hydrophones
4 hydrophones
8 hydrophones
3 hydrophones
6 hydrophones
10 hydrophones
Array development
Acquired RESON hydrophones
Developed PIC based hydrophone control
Array construction under way
Conclusions
Understood and mathematically modelled hydrophone system
Successfully generated bipolar acoustic pulses in laboratory and pool conditions
Ongoing Rona data analysis Array development Pancake detection
Thank you
Questions ?
http://pppa.group.shef.ac.uk/acorne.php
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