Study of the acoustic fieldgenerated by the electron beam in water

Olga Ershova

July, 19th 2006INFN Genova

Acoustic neutrino detection

• Proposed in 1957

• Detection of acoustic signals produced by neutrino-induced showers in water

• E > 1015 eV

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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:

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Thermal mechanism of sound generation in water

Neutrino produces а hadronic shower

Heat release localizedalong the shower

Instant volume expansion

Pressure wave

XN )(µ

νµ 4 / 24

Energy deposition area(for E = 1020 eV):

d = 20 cm

L = 20 m

Area of signal propagation:

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Acoustic signal characteristics

Bipolar shape1.

Max = 10 kHz

E > 1015 eV:f = 1 - 100 kHz

Frequency range2.

E = 1020 eVhadronicshower

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• Brookhaven NL, Harvard (1979)• ITEP (2004)

• INR (1987)• MSU SINP (2006)

Acoustic experimentson 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

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Acoustic experimentsin MSU

(April - May 2006)

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MSU electron accelerator

E 50 MeV

Beam duration 5 µs

Beam repeat time 10 Hz

Beam current ~ 3 mA

N 9·1010 particles / spill

E (total) 1018 eV

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MSU electron accelerator(RTM-70)

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Modeling

• Proton beam(d = 2 cm, E = 200 MeV, N = 4·1010)

• Electron beam(d = 4 mm, E = 50 MeV, N = 9·1010)

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Mean energy loss per path length unitof protons and electrons in water

Z, mm

dE/d

Z, M

eV/m

m

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Z, mm

X, m

m

Energy loss, MeV/mm3

Protons

Mean energy loss per unit of volume

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Z, mm

X, m

m

Energy loss, MeV/mm3

Electrons

Mean energy loss per unit of volume

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Transverse distribution of energy loss for several beam cross-sections

Протоныбез коллиматора

Electrons

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Experimental set-up

945 mm 508 mm

523

mm

46 mm

beam

hydrophone hydrophone

Y Y

Z X

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Acoustic Basin 100x50x50 cm3

Beam pipebeam

Scanner(step = 4.5 mm)

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Piezoelectric hydrophonesused for the measurements

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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.

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Amplifier 150 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

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Recorded acoustic signal(x = 6 cm, step 10)

Hydrophone

Beam currenttransformer

40 µs, R=6 cm

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Beam current calculated for each measurement

Signals normalized to 1 mA beam current

Plotted one under anotherwith 1 step distance between them

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beam

Space-time structureof 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

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Space-time structureof the acoustic field (z = 20 cm)

beam

X = 0 cm

X = 30 cm

hydrophone

Z = 20 cm

Z

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