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Measurements and Simulation Studies of Piezoceramics for Acoustic Detection

Measurements and Simulation Studies of Piezoceramics for Acoustic Detection. Karsten Salomon Universität Erlangen-Nürnberg. Motivation. Development and simulation of calibration sources for acoustic detection Simulation of detector devices

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Measurements and Simulation Studies of Piezoceramics for Acoustic Detection

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  1. International ARENA Workshop at DESY, Zeuthen May 2005 Measurements and Simulation Studies of Piezoceramics for Acoustic Detection Karsten Salomon Universität Erlangen-Nürnberg

  2. Motivation • Development and simulation of calibration sources for acoustic detection • Simulation of detector devices • Understanding of the whole system emitter to receiver (finding the transfer functions) K. Salomon, Universität Erlangen-Nürnberg International ARENA Workshop, May 2005

  3. Sources for Calibration for Acoustic Particle Detection Electric bulbs Heated wires Laser Piezos K. Salomon, Universität Erlangen-Nürnberg International ARENA Workshop, May 2005

  4. Piezoelectric Effect • Equation of motion of piezos is complicated - coupled Partial Differential Equations (PDE) of an anisotropic material: • Hooke’s law + electrical coupling • Gauss law + mechanical coupling • Finite Element Method chosen to solve these PDE K. Salomon, Universität Erlangen-Nürnberg International ARENA Workshop, May 2005

  5. Displacement • Motivation: Calibration of sound source to measure the sensitivity of the hydrophone • Simulation: Displacement of a piezo disc due to electrical voltage is simulated for different frequencies using CAPA K. Salomon, Universität Erlangen-Nürnberg International ARENA Workshop, May 2005

  6. Schematic of the Interferometer • Measurement: Direct measurement of the displacement with a self built fibre coupled interferometer • Multiple reflections between piezo and fibre ending K. Salomon, Universität Erlangen-Nürnberg International ARENA Workshop, May 2005

  7. 2cm Setup of the Interferometer K. Salomon, Universität Erlangen-Nürnberg International ARENA Workshop, May 2005

  8. dx Photodiode Voltage (V) dUPhoto -/8 0 /8 Actuator Voltage (V) Calibration of the Interferometer • Description possible with geometric series • dU proportional dx • Calibration before each measurement • Photodiode voltage proportional to intensity • Precision of ~0.1nm K. Salomon, Universität Erlangen-Nürnberg International ARENA Workshop, May 2005

  9. Displacement - Results • Measurement: white noise applied to Piezos • Simulation: Finite Element Method • Eigenfrequencies -->no flat frequency response K. Salomon, Universität Erlangen-Nürnberg International ARENA Workshop, May 2005

  10. Sending Signals with the Piezo • Frequency response -> response to arbitrary signal • As a source for calibration a pressure signal is needed • How does the movement of the piezo result in a defined pressure signal? • Small excursion: signal production in water K. Salomon, Universität Erlangen-Nürnberg International ARENA Workshop, May 2005

  11. Signal Production in Water • Signal propagation in water is described with a wave equation • If the sent wavelength is larger than the dimension of the transmitter, then: • Change in volume dVA dx • Equation for pressure: • Displacement of piezo is proportional to the applied voltage • Outside resonances, the second derivative of the applied voltage will be sent K. Salomon, Universität Erlangen-Nürnberg International ARENA Workshop, May 2005

  12. Direction Characteristics:Simulation and Measurement • Simulation of a piezo disc R=7.5mm H=5mm • Coupling of the piezo displacement to water • Acoustic field after 20 µs when applying a 20kHz sine: K. Salomon, Universität Erlangen-Nürnberg International ARENA Workshop, May 2005

  13. Direction Characteristics:Simulation and Measurement Simulation Measurement K. Salomon, Universität Erlangen-Nürnberg International ARENA Workshop, May 2005

  14. Impedance of the Piezo: Simulation and Measurement • Motivation: • Understand electrical properties of the piezo • Calculate parameters for equivalent circuit diagram • Simulation • Apply charge pulse to the piezo. • Calculate voltage response. • Impedance is given in the frequency domain as: K. Salomon, Universität Erlangen-Nürnberg International ARENA Workshop, May 2005

  15. Impedance of the Piezo: Equivalent Circuit Diagram • First resonance and antiresonance of a piezo can be described with an equivalent circuit diagram: • L,C and R are equivalent to mass, stiffness and damping • With these parameters one gets a simplified piezo model K. Salomon, Universität Erlangen-Nürnberg International ARENA Workshop, May 2005

  16. Impedance of the Piezo: Simulation and Measurement • Far from resonances, the piezo acts like a capacitor Z~1/f K. Salomon, Universität Erlangen-Nürnberg International ARENA Workshop, May 2005

  17. Measurement: Displacement of a Commercial Hydrophone • Measurement with Laser Doppler Vibrometer K. Salomon, Universität Erlangen-Nürnberg International ARENA Workshop, May 2005

  18. Measurement: Displacement of a Commercial Hydrophone K. Salomon, Universität Erlangen-Nürnberg International ARENA Workshop, May 2005

  19. Summary • Summary: • Simulation in good agreement with measurement of piezos • Signal propagation in water described by simulation • Ideas how to calibrate hydrophones with impedance measurements • First steps how to calibrate hydrophones with displacement measurements K. Salomon, Universität Erlangen-Nürnberg International ARENA Workshop, May 2005

  20. Thanks for your attention K. Salomon, Universität Erlangen-Nürnberg International ARENA Workshop, May 2005

  21. The Finite Element Method • Numerical method to solve PDE with boundary value problems • Areas are discretisized into cells (finite elements) • Within a finite element characteristic functions are defined • Linear combinations of these functions then give possible solutions within an element K. Salomon, Universität Erlangen-Nürnberg International ARENA Workshop, May 2005

  22. Measurement: displacement of the HTI • Measurement with a Laser Doppler Velocimeter • Clearly seen a Peak at 57kHz but • Measurement: send different gaussians with HTI and receive with same type of HTI. Calculate Transferfunction: K. Salomon, Universität Erlangen-Nürnberg International ARENA Workshop, May 2005

  23. Measurement: displacement of the HTI • Explanaition: Additional damping due to water not completely known. K. Salomon, Universität Erlangen-Nürnberg International ARENA Workshop, May 2005

  24. Emulating a Neutrino Signal • Calculated neutrino signal in 400m distance following the thermoacoustic model for a 1PeV shower. • Send two times integrated neutrino signal K. Salomon, Universität Erlangen-Nürnberg International ARENA Workshop, May 2005

  25. Signal in frequency space Frequency response of the piezo Displacement using this Signal • But: Amplifiing the frequencies at the resonances • Send: • Simpler: Use a piezo with relatively flat frequency response Measurement Simulation K. Salomon, Universität Erlangen-Nürnberg International ARENA Workshop, May 2005

  26. Receiving the Bipolar Signal Signal Measured Second deriv. of signal K. Salomon, Universität Erlangen-Nürnberg International ARENA Workshop, May 2005

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