1. Study of the acoustic field generated by the electron beam in water Olga Ershova July, 19 th 2006 INFN Genova

2. Acoustic neutrino detection Proposed in 1957 Detection of acoustic signals produced by neutrino-induced showers in water E > 10 15 eV 2 / 24

3. Two methods of neutrino detection Light attenuation length ~ 20-40 m Sound attenuation length ~ 1 km Large effective volume of the detector is achievable with reasonable number of acoustic sensors Cherenkov detection: Acoustic detection: 3 / 24

4. Thermal mechanism of sound generation in water Neutrino produces а hadronic shower Heat release localized along the shower Instant volume expansion Pressure wave µ νµνµ 4 / 24

5. Energy deposition area (for E = 10 20 eV): d = 20 cm L = 20 m Area of signal propagation: 5 / 24

6. Acoustic signal characteristics Bipolar shape 1. Max = 10 kHz E > 10 15 eV: f = 1 - 100 kHz Frequency range 2. E = 10 20 eV hadronic shower 6 / 24

7. Brookhaven NL, Harvard (1979) ITEP (2004) INR (1987) MSU SINP (2006) Acoustic experiments on the accelerators protons electrons The only way to study acoustic effects from particle showers are the accelerator experiments in intense beams of protons and electrons 7 / 24

8. Acoustic experiments in MSU (April - May 2006) 8 / 24

9. MSU electron accelerator E50 MeV Beam duration5 µs Beam repeat time 10 Hz Beam current~ 3 mA N9·10 10 particles / spill E (total)10 18 eV 9 / 24

10. MSU electron accelerator (RTM-70) 10 / 24

11. Modeling Proton beam (d = 2 cm, E = 200 MeV, N = 4·10 10 ) Electron beam (d = 4 mm, E = 50 MeV, N = 9·10 10 ) 11 / 24

12. Mean energy loss per path length unit of protons and electrons in water Z, mm dE/dZ, MeV/mm 12 / 24

13. Z, mm X, mm Energy loss, MeV/mm 3 Protons Mean energy loss per unit of volume 13 / 24

14. Z, mm X, mm Energy loss, MeV/mm 3 Electrons Mean energy loss per unit of volume 14 / 24

15. Transverse distribution of energy loss for several beam cross-sections Протоны без коллиматора Electrons 15 / 24

16. Experimental set-up 945 mm 508 mm 523 mm 46 mm beam hydrophone Y Y Z X 16 / 24

17. Acoustic Basin 100x50x50 cm 3 Beam pipe beam Scanner (step = 4.5 mm) 17 / 24

18. Piezoelectric hydrophones used for the measurements 18 / 24

19. Points of measurement 6 linear tracks: I,II,III,IV along the beam axis, V,VI - across. I,II,III,IV: 100 points; V,VI: 40 points. The step is equal to 4.5 mm. 19 / 24

20. Amplifier 1 50 dB 20 - 200 kHz hydrophone Beam current transformer computer Electric diagram Amplifier 2 10 dB 10 - 100 kHz Oscilloscope Observation time: 1 ms Digitization frequency: 10 MHz 650 oscillograms recorded 20 / 24

21. Recorded acoustic signal (x = 6 cm, step 10) Hydrophone Beam current transformer 40 µs, R=6 cm 21 / 24

22. Beam current calculated for each measurement Signals normalized to 1 mA beam current Plotted one under another with 1 step distance between them 22 / 24

23. beam Space-time structure of the acoustic field (x = 6 cm) Signal from the beam point closest to the hydrophone Signal from the area of beam entrance beam Z = 0 cm X Z = 40 cm hydrophone X = 6 cm 23 / 24

24. Space-time structure of the acoustic field (z = 20 cm) beam X = 0 cm X = 30 cm hydrophone Z = 20 cm Z 24 / 24