Sonoluminescence
Apparatus
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photo:
Julio da Graca is making adjustments to the SBSL apparatus. The cylindrical water-filled resonator is visible. |
Our ultimate objective is to understand
the light emission mechanisms of SBSL(single bubble
sonoluminescence). The
presence of a noble gas in the trapped bubble is known to be
important for strong emission of light. The question we are
addressing currently is what happens if two noble gases are present
in the bubble. In the presence of large temperature and pressure
gradients, the two noble gases are expected to segregate according
to the mass differences. As
we vary the mixing ratio and noble gas species(He, Ne, Ar, and Xe)
in the bubble, we are measuring:
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A
schematic set up of our SBSL apparatus
The
cylindrical cavity is made up by a quartz tube (75 mm inner diameter and
80 mm long) and two brass end plates.
A pair of piezoelectric transducers (PZT) are epoxied onto the end
plates. The PZTs excite a
resonance in the cylindrical resonator at 17.3 kHz.
A mixture of noble gases has been dissolved into the water.
A gas bubble is created by passing a pulse of current into the
heater wire. The bubble can
be levitated at the anti-node of the resonance if the acoustic amplitude
is sufficiently high. When
the acoustic amplitude is increased further beyond certain threshold,
light emission can be seen with naked eyes.
When the acoustic amplitude exceeds a second threshold, the bubble
becomes unstable, breaks up and dissolves back into water. The photodiode is used to monitor the light emission intesity.
