SBSL is a recently discovered phenomena [by P. Gaitan, 1988] and is currently a subject of much theoretical and experimental interest.
In SBSL, a single, micron-sized gas bubble is levitated (trapped) at the center of a cell containing water or other appropriate liquid by the acoustic pressure of vibrations applied at the resonance frequency of the apparatus. Under certain conditions, the bubble collapses while being violently driven, setting off (launching) a highly spherical shock wave towards the center of the bubble. A phase transition occurs whereby the bubble's gas reaches extremely high temperatures (5000 to 50,000 Kelvin) and is seen to emit bluish-white light in synch with the driving acoustic frequency. The turn-on time of the bubble during its collapse is extremely rapid (less than 50 psec) and it is also extinguished very rapidly --in less than 34 psec. The jitter between adjacent pulses is quite small, less that 50 picosecond, which is much smaller than the jitter in the driving acoustic force itself.
A CCD image of the 100 ml flask used as the SBSL cell. The two piezoelectric crystals which provide the acoustic driving force are epoxied in place on opposite sides of the cell, and a small pickup-microphone crystal is attached beneath to monitor the resonance vibrations. The resonant frequency of this cell with H2O at STP is ~ 21 KHz. The wires to the crystals are very thin and attached with indium solder. They were coated with glyptol for additional electrical insulation. The water is deaereated by pumping on it for 20-30 minutes in a bell jar.
A CCD image of two oscilloscopes' traces. The top trace is the response of the pickup microphone at resonance before a bubble has been trapped. Note the smooth character of the sinusoidal trace. Below are the traces of the current sense(the larger trace) and the voltage sense (smaller trace) for the electrical driving circuit. Once the main acoustic resonance frequency is found, an adjustable inductor in the electrical circuit is tuned to achieve phase synchronization of the current and voltage sense of the circuit. When this is achieved the amplitudes of all three traces increase significantly.
These are CCD images of the same two oscilloscopes as above. However, now a bubble has been induced/placed inside the cell. Note the 'shoulders' and sub-tones that have appeared on the formerly smooth sinusoidal microphone trace.
