Sonoluminescence

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Sonoluminescence

• The Star in a Jar

A journey of 4 men through the jungle of
experimental physics. The highs. The lows. The
resultsand the lack of results.
Sonoluminescence
Us
llll
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Adam Fox
Brendan Lyons
Dan Moulton
Jonathan Fulton
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The Theory

• A loud, high frequency sound traps bubbles in the
  resonance of a container
• Bubbles expand and contract in a periodic manner,
  and they give off short bursts of light

(1)
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Why?

• An approximation of Navier-Stokes Equations gives
  a good estimate of the motion of the bubble

(1)

• Why the light?
• Possible theories hotspot, collision induced
  radiation, proton tunneling etc.
• Reallythis is undecided.

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Our initial setup

• Piezo-electric transducers drive a cylinder at
  acoustical resonance
• Over 700 V peak to peak is required across the
  transducers
• A microphone is attached to the cylinder to
  measure what is going on inside the system.
• An RLC circuit is used to resonate at the same
  frequency as the resonant frequency of the flask.

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Drive Transducer
Microphone
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The circuit
Tuned Inductors
(2)
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To attain electrical resonance

• A network of inductors was used.
• W0 1 / Sqrt(LC)

Coil of wire
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To attain acoustical resonance

• The signal generator is used to sweep through
  frequencies until the highest reading on the
  microphone is attained
• Acoustical resonance of the cylinder is about
  11.5 khz, which is in the range of hearing.

(the wave equation)
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The problems

• It is extremely difficult to fill the flask with
  completely degassed water, which is essential to
  achieve sonoluminescence
• The resonant frequency was in our range of
  hearing.

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Solution

• We moved to a spherical flask.

(3)
Acoustical Resonance about 23.5 khz
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More problems

• It is extremely difficult to tune to electrical
  resonance
• We had no ferrite rod, only steel.
• The fringe effects on the solenoid causes enough
  inaccuracy.
• So, we dont get nearly enough voltage across the
  transducers.

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More solutions

• A Yamaha Model A-550 was found and used to
  further amplify the signal
• This acts as a tunable transformer. Combining
  this with the 15, we were able to get the
  required 700 Vp-p across the transducers!

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(No Transcript)
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(Picture stolen from http//www.techmind.org/sl/,
then modified)
33mH Inductor
Stereo Amp
Audio Amp
V
Signal Generator
(2)
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Preparation of the water
Deionize
Degas
Also, the water should be quite cool (0-10
degrees C)
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After a few attempts
Our best trial run gave

• Resonant frequency of the flask (measured)
  23.406 khz
• Voltage across transducers 707 V
• Microphone signal (measured w/oscilloscope) 3.58
  Vp-p

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To insert a bubble

• A small syringe is used to remove some liquid,
  and then inject one or two small bubbles on the
  surface

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Ideally...

• If the flask is being driven at acoustical
  resonance, small bubbles will move from the
  surface to the center of the flask
• The bubble at the center will give us
  sonoluminescence.

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What happened to us

• No bubbles were observed to move to the center,
  although the oscilloscope reading suggested that
  there were bubbles injected into the liquid
• Small distortions on scope

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Perhaps?

• It is possible that we actually were able to
  successfully create this sonoluminesence, but we
  werent able to observe either the bubble or the
  light.
• Our method of injecting bubbles was flawed, and
  it disturbed the system too much (bubbles
  sticking to walls, etc).

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• Thanks to Lyman and Wei for providing much-needed
  help, teaching us how to use the electrical
  equipment, etc.
• This course taught us that experimental physics
  is extremely hardbut it provides the best
  opportunity for active learning.

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Bibliography

• http//en.wikipedia.org/wiki/Sonoluminescence
• http//www.techmind.org/sl/
• http//sps.nus.edu.sg/pokailin/acad/72.pdf