I'm curious as to what the strangest/most unique discoveries people have had over the years. The discovery doesn't necessarily have to have been published either. It can just be something strange that you noticed.
In my laboratory we use Nd:YAG lasers with a 5 nS pulse at 532 nm to do various photoacoustic experiments via optical fiber (standard 1000 um fiber from Thorlabs) to deliver the laser light. I've noticed that under some peculiar alignment circumstances (if the fiber isn't cleaved perfectly flat) the fiber will guide yellow light that I can see through the glasses that block 532 nm at the end of the fiber when I direct the beam into some normal white paper. I checked the laser to make sure that it isn't outputting anything other than 532 nm (it isn't) and I checked to see what colors were being output after the fiber and it was 532 nm along with 543 nm and others. The strange thing was that the light was not constant, on some pulses it would just be 532 nm, on others it would be a mixture. In addition, I checked to make sure that the paper was not fluorescent at 532 nm (it's not). The only thing that changed the yellow light was realigning the fiber.
I figured it was some sort of RAMAN effect, but to me that was the strangest thing I've seen in the lab.
For me, it was a plasma doughnut - I have never been able to reproduce it, but it is really doughnut shaped, as I took some pictures with a digital camera and the form is still the same (I did that, because first I thought it might be a so-called plasma fireball which is rotating around the edge of a circular anode, but that woud mean that I do not see the very same picture every time - i.e. the brightest spot should change it's position, but it doesn't).
It appears also not to be a very thick sheath, as the sheath size at this pressure/plasma density (p ~ 10^-3 mbar, n_e ~ 10^15 /m³) should be smaller than 1 mm, while here the doughnut is several cm thick. Furthermore a sheath would sit symetrically around the round wire electrode, which is not the case here - in fact it sits on top of it.
Wow, that is very cool! Is there anything in the literature describing the ability to make a plasma doughnut as of yet?
Hi Benjamin,
no, not to my knowledge - the problem is that, as I said, I was never able to reproduce it. The problem is that those anode phenomena is highly non-linear and even chaotic.
I tried to recreate the experimental conditions (and that I was able to do within the accuracy of my instruments), but still I could not obtain such a doughnut shape.
I would have to search my computer, if I still have the experimental conditions somewhere, because I changed the institute meanwhile and I am not sure, if I can still find the data on my laptop.
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