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Hydrophone based calibrator for seawater acoustic detection of UHE neutrinos

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.

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Hydrophone based calibrator for seawater acoustic detection of UHE neutrinos

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  1. 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

  2. Outline • Rona array • DAQ • Calibration • Pinger development • Deployment • Future work

  3. 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

  4. Rona hydrophone array • 8 hydrophones • Low noise preamplifiers • 1200m x 200m at mid depth in 230m deep sea • Hydrophone positioning off during data readout

  5. Quantum Superloader 3 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

  6. 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

  7. Calibrator development - progression Laboratory tank Swimming pool Open sea (Rona) Development Lake (Kelk)

  8. Calibrator development - tools Tx – omnidirectional ± 1.8dB @ 10kHz Rx - flat frequency response

  9. (hydrophone) input output system & output => excitation pulse Signal generation - system Know system and desired output to deduce required excitation pulse Convolution integral (t) y(t) = x(t) * h(t) - complicated Convolution (s) - freq. domain Y(s) = X(s) . H(s) Inverse FFT y(t) = IFFT(Y(s)) Impulse response not practical use step response Step response = time integral of impulse response Time domain Discrete time signal Impulse Step

  10. d / dt Hydro system H(t) Imp. resp. step o/p Signal generation - signal Deconvolute i/p from sys. & o/p X(s) = Y(s) / H(s) Transform to time domain x(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

  11. Pool – hydrophone modelling • Hydrophone step response is recorded at various distances and dejittered

  12. 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

  13. Technique verification

  14. Excitation signal • Desired acoustic pulse and the estimated hydrophone driving electrical signal Generates 10 Pa @ 1m

  15. Pool - bipolar acoustic pulse Measured at various distances

  16. Rona - field trip • The joys of British “Summer”

  17. 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

  18. New excitation signal See Bevan et al. – parameterisation: more energy at core of the shower Restrictive by the hydrophone linearity potentially, can generate up to approximately 60 Pa @ 1m

  19. Array hydrophone count 2 hydrophones 3 hydrophones 4 hydrophones 6 hydrophones 8 hydrophones 10 hydrophones

  20. Array development • Acquired RESON hydrophones • Developed PIC based hydrophone control • Array construction under way

  21. 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

  22. Thank you Questions ? http://pppa.group.shef.ac.uk/acorne.php

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