After a few months of trying to get all the right equipment in the right place and not on fire at the same time, I've finally managed to ignite sonoluminescence. Obligatory proof photo:
Yes, that is a tablet case in the background. It's the only black thing I could find at the time [1], OK? Sheesh. This was taken in the darkest conditions I could manage in the room; the room looks all glowy-like because this was a 4 second exposure. It's really quite surprising to see how much more sensitive our eyes are than cameras at low-light conditions: when everything is tuned up correctly, you can see the glowing bubble quite readily with the naked eye. But even through a magnifying glass, the point-and-shoot camera I was using saw nil on video mode and normal picture mode.
Credit where credit is due; one of the best resources for this phenomenon is techmind.org/sl. I drew a lot of information from this site, and the chart of transducer levels to bubble regimes was particularly useful. I actually used a rather different setup than he did, but it's possible that his system would be easier to setup for some.
The components I used:
Transducer:
I used one single 25khz 60w piezo ultrasonic cleaning transducer bought off ebay, which ran me about $20. I don't seem to be able to find the original seller. I originally used a small piezo disk (glued somewhere on the flask) as a sense transducer, which worked very well until I destroyed it.
Amplifier:
I tried a 100w 28khz ultrasonic cleaner driver board, with the intent of hacking into the oscillator and de-tuning as necessary, but this didn't work out as I imagined, even though the very helpful ebay supplier supplied his schematic. Also, as a result of me being rather reckless with 115v systems, I lost a few pieces of equipment trying to use this. Also I blew two of the driver boards up quite spectacularly, but we won't talk about that.
I ended up using a regular audio amp (I used a 7 watt kit from sayal, but other ones turned out to work just as well), connected to a 115v-6.3v line transformer run backwards, with the 115v side connected to the transducer, and the 6.3v side to the amp.
Signal generator:
I purchased a velleman HPG1 signal generator, which was 150 dollars very well spent. I did manage to blow the output op-amp nary an hour after I got it, but that was a relatively easy fix. As were the next two times I blew it up.
Flask:
This ended up being quite important. I initially tried an off-round flask from Sayal, but this didn't have any sort of reasonable resonance. Don't get anything that isn't spherical, because they won't even. I found a completely spherical distillation flask at amazon, which worked quite nicely indeed. I tried the 50ml version first, but the resonance was at too high a frequency, outside my amplifier's range. The 150ml version worked perfectly, and is what you see in the photo above.
The setup was very easy; connect some 12v power supply, amp, transformer, and transducer, glue the sense transducer and the power transducer onto the flask, and it's done.
The device only consumes about 1.1 watts while operating, which includes a large loss from the amplifier.
Now I just need to experiment around with it. Suggestions welcome for experiments I should do!
From Putterman et al, we see that about 10^6 photons are emitted in each acoustic cycle (taken from the techmind page).
[1] The black baffle was required to stop light from the signal generator's 10e42 watt apparent brightness LED backlight, which cannot be disabled or dimmed at all. All it would take is five lines of code and one single transistor.....
