Overview of Sonoluminescence project at Academia Sinica Fong-Kai Lin 林楓凱 In Seoul 2007/11/24 INSTITUTE OF PHYSICS, ACADEMIA SINICA, TAIWAN

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 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 R max ~ 100 R min V max ~ V min The bubble at center of spherical flask has a radial motion, and within a period of PZT, 1/25000 second (strictly speaking, within 1/ 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). Blackbody law tell us what temperature will reflect this ratio. About 15000~20000K

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.