Testing thermo-acoustic sound generation in water with proton and laser beams

Transcription

1 International ARENA Workshop DESY, Zeuthen 17th 19th of May 25 Testing thermo-acoustic sound generation in water with proton and laser beams Kay Graf Universität Erlangen-Nürnberg Physikalisches Institut I - Förderschwerpunkt Astroteilchenphysik Großgeräte der physikalischen Grundlagenforschung

2 Aims study sound generation mechanism of intense pulsed beams test thermo-acoustic model - simulation based on it use as absolute calibration source for hydrophones use intense pulsed proton and laser beams acoustic wave beam pulse water tank hydrophone DAQ Kay Graf 1 Universität Erlangen-Nürnberg

3 The Theoretical Model The thermo-acoustic model (G.A. Askaryan et al. 1979) wave equation: P ( r, t) 1 c 2 s 2 P ( r, t) t 2 = α 2 ɛ( r, t) C p t 2 solution (Kirchhoff integral): P ( r, t) = 1 4π α C p dv r r 2 ( t 2 ɛ r, t r r ) c s Parameters controllable in experiments P ( r, t) α, C p, c s ɛ( r, t ) pressure measure at different locations volume expansion coefficient, heat capacity, speed of sound measure at different water temperatures energy deposition density use different beam types, profiles and energies Kay Graf 2 Universität Erlangen-Nürnberg

4 6cm tank hydrophone beam coordinates z beam entry into water (x=cm, z=cm) 15cm x pulse The Test Setup I adjustable beam pipe adjustable Aluminum tank: cm 3 (ca. 45 l) positioning of sensors: in whole tank with a few mm precision water temperature: ca. 1 5 C with.1 C precision DAQ (not shown): digital readout up to 4 sensors simultaneously (1 MSamples/s, 8 bit) beam entry not at walls to seperate signal reflections Kay Graf 3 Universität Erlangen-Nürnberg

5 The Test Setup II Setup in action Hydrophones 1cm by High Tech, Inc. frequency range: 2 15 khz sensitivity: -155 db re V/µPa Kay Graf 4 Universität Erlangen-Nürnberg

6 The Proton Beam Experiment experimental hall beam line performed at Theodor Svedberg Laboratory (Uppsala, Sweden) in February 24 test stand beam exit together with groups of DESY-Zeuthen and Uppsala Univ. Kay Graf 5 Universität Erlangen-Nürnberg

7 overview The Laser Beam Experiment cabin beam line located at our institute always available power supply laser cabin interior beam exit test stand diploma thesis of S. Schwemmer, Erlangen Kay Graf 6 Universität Erlangen-Nürnberg

8 Experimental Parameters proton accelerator: Gustaf Werner Cyloctron at The Svedberg Laboratory laser: pulsed infrared Nd:YAG-Laser (Spectra Physics) parameter proton beam laser beam particle properties E p = 177 MeV λ = 164 nm penetration depth 22 cm (Bragg peak) 6 cm (absorption length) pulse energy 1 PeV.4 EeV.1 EeV 1 EeV pulse duration 3 µs 1 ns beam width.6 cm 2 cm 1 mm 1 cm pulse frequency 1 Hz.1 Hz 1 Hz signal shape dominated by pulse duration (proton beam) and beam width (laser beam) Kay Graf 7 Universität Erlangen-Nürnberg

9 Simulation of Acoustic Pulse I Energy deposition ɛ( r, t) proton beam laser beam Bragg peak (22cm) E [au] E [au] x [m] z [m] x [m] z [m] z-profile: simulated with GEANT4 xy-profile: gaussian (σ xy 5 mm) pulse shape: gaussian (σ t 6 µs) z-profile: exponential decrease (absorption length 6 cm) xy-profile: gaussian (σ xy 5 mm) pulse shape: gaussian (σ xy 1 ns, instantaneous) Kay Graf 8 Universität Erlangen-Nürnberg

10 pressure [Pa] z [m] Simulation of Acoustic Pulse II Sonic field and acoustic pulse (proton beam) beam x [m] pressure [Pa] z=12 cm x = 1cm x = 3cm x = 5cm x = 7cm x = 9cm time [ms] sonic field and acoustic pulse by numeric solution of wave equation for a beam pulse Kay Graf 9 Universität Erlangen-Nürnberg

11 signal [mv] charge effect start of acoustic signal Properties of Measured Signals Proton beam single signal averaged signal (1 ) ringing signal [mv] Laser beam 4 single signal ringing start of acoustic signal direct signal signal of beam entry time [µs] x 1 cm, z 12 cm, E.4 EeV (highest energy) main frequency 15 khz charge effect of proton beam little ringing of sensor time [µs] x 1 cm, z 2 cm, E.5 EeV (low energy) main frequency 6 khz no charge effect (photons) strong ringing of sensor Kay Graf 1 Universität Erlangen-Nürnberg

12 signal Measured Signal Shape vs. Simulation 2 simulated pulse [mpa] hydrophone response [au] measured signal [au] approach: simulate pulse transmit pulse with transducer in water receive hydrophone response of pulse compare with signal measured at proton beam time [µs] good agreement in shape sensor changes signal working on absolute calibration Kay Graf 11 Universität Erlangen-Nürnberg

13 Signal is Acoustic Proton beam Laser beam x [cm] time of maximum [µs] preliminary measured at same temperature, time offset corrected from slope: c s = 1458 ± 3 m s (Lit ± 1 m s ) Kay Graf 12 Universität Erlangen-Nürnberg

14 Energy Dependence signal amplitude [mv] Proton beam Laser beam puls energy [PeV] preliminary different slopes due to: different energy deposition profiles different pulse lengths 1% systematic uncertainty in energy determination different slopes expected (simulation) measured with same hydrophone expected linear dependence Kay Graf 13 Universität Erlangen-Nürnberg

15 signal amplitude [mv] near field Position Dependence preliminary x [cm] 28cm data fit data fit simulation far field data from proton beam experiment simulation and measurement match well (simulation matched to data at x = 1 cm) DISTANCE (METERS) Kay Graf 14 Universität Erlangen-Nürnberg SIGNAL AMPLITUDE (arbitrary units) Sulak et al., 1979 fit parameters: near field: x.57±.2 (sim: x.51±.3 ) far field: x.86±.2 (sim: x.88±.1 ) transition: 28 cm (sim: 27 cm)

16 signal amplitude [mv] data Temperature Dependence I Proton beam fit data (linear) temperature [ C] preliminary Laser beam temperature [ C] Kay Graf 15 Universität Erlangen-Nürnberg signal amplitude [mv] 6 data fit data (linear) fit simulation from α C p (normalisation arbitrary) preliminary preliminary - analysis ongoing! temperature dependence more linear than expected sensor or signal features? zero crossing at 4.5 ±.1 C (proton) and 3.9 ±.1 C (laser) (α: 4. C, Sulak et al. 1979: 6. ±.1 C, Hunter et al. 1981: 6 C) laser: zero crossing as expected by thermo-acoustic model protons: superposition with non-thermal pulse could explain behaviour

17 signal [mv] Temperature Dependence II Averaged proton beam signals preliminary C C 3.9 C C time [µs] Single laser beam signals time [µs] Kay Graf 16 Universität Erlangen-Nürnberg signal [mv] C preliminary - analysis ongoing! inversions of signals clearly visible ( C) for protons: pulse shape changes, signal amplitude never zero signals confirm amplitude behaviour 4.4 C 3.9 C 3.4 C preliminary

18 Summary and Outlook Summary proton and laser beam experiments confirm: high-precision data thermo-acoustic sound generation is primary effect simulation and expectations in good agreement with measured signals Outlook some minor effects (around 4 C) need to be clarified work on the calibration of sensors ongoing use laser as calibration source Kay Graf 17 Universität Erlangen-Nürnberg

19

20 Thermo-acoustic Sound Generation sonic disc ν L~5m d~5cm hadronic cascade ~1km ν hadronic cascade water gets heated and expands energy dissipates hydrodynamically acoustic pulse Kay Graf 19 Universität Erlangen-Nürnberg