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Overview of Sonoluminescence project
at Academia Sinica
Fong-Kai Lin 林楓凱
INSTITUTE OF PHYSICS, ACADEMIA SINICA, TAIWAN
In Seoul 2007/11/24
Outline
Background Introduction
 Research Directions
 Future Work
 Summary

Background Introduction

Compressing things very quickly causes
temperature to go up.

Single-bubble sonoluminescence occurs when
an acoustically trapped and periodically driven
gas bubble collapse so strongly that the energy
focusing at collapse leads to light emission .
How do we do it?

PZT is a ceramics capacitance
with very special electric property :
expand or contract itself by changing
direction of current.


We stick two PZTs on a spherical
flask then change current direction
25000 times per sec. Wall of
flask will oscillates with PZT ,
if there’s liquid in flask, pressure field would be built, any bubble
in the liquid will be pushed to center of this spherical flask.
When wall of flask move inward (outward), a positive (negative)
pressure wave propagates to bubble, bubble is compressed
(expanded)
Radial Motion
The bubble at center of
spherical flask has a radial
motion, and
Rmax ~ 100 Rmin
Vmax ~ 1000000 Vmin
within a period of PZT,
1/25000 second
(strictly speaking, within
1/200000 second)
Compressing things very quickly…
Gas inside the bubble burns !!
 It looks like a star in the dark sky, with blue
or white shine.

Experimental Setup
Radius vs. Time

In most of time, the
bubble expand its
volume, then collapse
suddenly. It emits light
when minimum volume
reach.
A Controversial Experiment
Taleyarkh
an
Sun in a Jar
Burning Bubble Brings Burning Questions…
What’s the best applied frequency that
drives the bubble in efficient way?
 What’s the temperature inside the bubble?

Research Directions (1)

Phase-change phenomenon :
Sweep the frequency in suitable region, the
pressure that SL bubble undergoes can be
positive and, especially, negative.
It seems that the bubble emits light when it is
expanding!
Changing Phase
Experimental Result
Light Yield Efficiency
Research Directions (2)



To measure temperature inside the bubble directly by
scintillator quinine :
The twinkling bubble is too small to detect some
important physical qualities directly, especially
temperature. High energy photon (<400nm) cannot
escape from liquid . We use quinine (solved in water) to
transfer high energy photon into visible light for building
complete spectrum, so that temperature can be
evaluated by blackbody law.
Absorption of high energy photon and emits visible light
needs time, signal of PMT with a “tail” is expected.
Typical Pulse Shape of Quinine –Doped Water



The difference of green and
red signal is contributed by
blue part. It stands for high
energy photon that cannot be
seen before.
By computing ratio of normal
and quinine pulse area in red
part, we get ratio of high
energy part (fluorescence
,<400nm) and normal part
(SL,>400nm). Blackbody law
tell us what temperature will
reflect this ratio.
About 15000~20000K
 Tot (t )  [1   ]   SL (t   SL )     FL (t   FL )
Blackbody Spectrum
Future Work (1)

Multi-bubble Sonoluminescence :
In some acid liquid, many bubbles can co-exist, one bubble can
affect another by small motion. What’s the relationship between
pulses time interval, spatial distribution of bubbles and light-yields ?
Future Work (2)

Measuring temperature of bubble gas has
developed complete, now will combine
with changing-phase exp. To explore how
high energy photon ratio change with
frequency.
Summary
All the technique is built in AS and much
data has taken, more and more physics is
waiting for analyzing.
 Sonoluminescence is a highly nonlinear
phenomenon, some experimental result is
hard to explain, we have long way to go.
 And it’s cheap compared with high energy
physics experiment.
