[ArtAndScience (OP)]

Hello!
This is my first post here. I am a digital artist who develops interactive learning for science and engineering subjects, hence my ID.  Today, I built a simple 'cloud chamber' to detect atomic particle tracks--a photo is below. The particle source I used is a small button of Am-241. Most of the tracks I observed seem to be either straight (alpha?) or curved (beta particles?). The one exception is the bulls-eye pictured below, with two lobes (arrows). I have never seen such a track in a cloud chamber--do you have any idea what it is?

[RD]

The bullseye seems to correspond with the shape and size of the radioactive button ...

 [ Invalid Attachment ]

Perhaps the button was sitting there previously and has made the floor of the chamber radioactive in a bullseye pattern.
[ The smaller rings at 12 & 2 o'clock, (the "lobes") ,  could be caused by the button being turned the other way up from its current position ].

NB: Americium 241 also emits gamma radiation which does not produce tracks in a cloud chamber,
but gamma rays which hit your apparatus to could then cause it to emit electrons which in turn cause clouds to form in your chamber ... http://chambrebrouillard.wifeo.com/gamma.php

Americium from smoke detectors is not good for ones complexion ...



http://www.foxnews.com/story/0,2933,292111,00.html

[ArtAndScience (OP)]

The bullseye seems to correspond with the shape and size of the radioactive button ...
Perhaps the button was sitting there previously and has made the floor of the chamber radioactive in a bullseye pattern.
[ The smaller rings at 12 & 2 o'clock, (the "lobes") ,  could be caused by the button being turned the other way up from its current position ].

Thanks RD for your reply. Yes--that's the very first thing I asked myself; so I went back to the original pictures to verify.
(Note that my picture above is a composite of tracks from photos bracketed at approx. 1 sec. intervals.

Following is the original picture of what I call the "bull's eye" and the picture 1 second preceding and one second following. Obviously, the button has not moved, and the bull's eye was visible for a fraction of a second--it's only pure chance it was photographed. Since this pattern has a similar appearance to already familiar ionized trails of particles, it's logical to ask if ionizing radiation created this very brief pattern too. When I saw this pattern and corresponding trails, I wondered if tracks are visible when an atom nucleus is struck by a heavy particle? Or if an atom fissioned in a chamber, would anything be visible?  I have no evidence for this hunch, other than similar tracks I've seen in particle accelerators. Whatever made this track, I consider myself lucky to have recorded it.     Note--most of the "button" is an aluminum housing, not the 0.9 microcurie of Am-241. So I don't look like that guy in the picture, fortunately.

The sequence of pictures--at approx. 1 sec intervals.

[RD]

... the bull's eye was visible for a fraction of a second--it's only pure chance it was photographed ...

Perhaps the conditions in the cloud chamber which showed the radioactive footprint(s) of the button's previous position(s) only existed momentarily.

Double-exposure / after-image, ( like "ghost" aeroplanes on Google maps ), doesn't work as an explanation as the shape of the button isn't visibly a ring from the angle we're viewing it at.

Gamma-rays can fog film (and the digital equivalent), but even if you had placed the button on the back of the camera earlier it would produce a circular not elliptical shape.

[ArtAndScience (OP)]

... the bull's eye was visible for a fraction of a second--it's only pure chance it was photographed ...

Perhaps the conditions in the cloud chamber which showed the radioactive footprint(s) of the button's previous position(s) only existed momentarily.

Gamma-rays can fog film (and the digital equivalent), but even if you had placed the button on the back of the camera earlier it would produce a circular not elliptical shape.

RD, perhaps I didn't explain myself clearly--but the "button" (an aluminum housing surrounding just 0.9 microcuries of Am-241) never was in that position, especialy within the time frame I carefully pictured above. Nor does this scenario explain why a "footprint" would appear and disappear within one second. But we have already established a mechanism for these short-timeframe events--the ionized trails of charged particles.

What I don't understand is why you want to pursue an explanation for the button as being the cause, simply because it's a vaguely similar shape--yet with no direct causality between these two have been recorded by me or established by this conversation. In fact, the button was never in that position, nor did it ever leave a ghost image nearer to the positions it was pictured--in literally thousands of photos I took to capture trails. As I stated before, since this bulls-eye has similarities to known vapor trails by sub-atomic particles, shouldn't scientific inquiry be directed at a possible particle explanation for this event?  To me, that seems to be the most straightforward and logical approach, rather than trying to conform my photographic data to one explanation. Well, that's as much effort I'm going to give on this thread. But if I find a similar event documented somewhere as a plausible explanation, I will update this thread. Cheers.

[RD]

...What I don't understand is why you want to pursue an explanation for the button as being the cause, simply because it's a vaguely similar shape-

Because it's a similar shape and size, (and it appears to be on the floor of the chamber).

Unless the button has always been fixed in the position shown, ( i.e. that it is impossible that it could have previously sat elsewhere in the chamber), then my original hypothesis is possible. The radioactive footprint created could easily exist for hours. The conditions your cloud-chamber may not be uniform, the conditions for clouds to form on the floor of the chamber could just occur intermittently, revealing the footprint momentarily.

If you're going to take further photographs you could conduct an experiment: place the button on a square of the material used to make the chamber, say overnight. Then place that square of irradiated material in the chamber vertically, rather than flat on the floor, so it is in a position where clouds will form readily, with the irradiated surface facing the camera.

[RD]

The "lobes" are vaguely similar to electron-positron pair created by a gamma ray , in an applied magnetic field ...

 [ Invalid Attachment ]
inset image http://www.nuffieldfoundation.org/practical-physics/beta-particle-tracks-bent-much-weaker-magnetic-field

The applied magnetic field is at least a thousand times stronger than Earth's natural magnetic field, so the tight spirals would not occur naturally. 

[ So I still think the bulls-eye is a radioactive footprint ].

[RD]

I've found cloud-chamber images with lobes and circles [ but these are in cloud-chambers with an applied magnetic field ten-thousand times that of Earth's, so I'm still sticking with footprint as an explanation ]

Bubble Chamber Image of "Charmed Baryon"  [includes petal-shaped lobes]
http://images.sciencesource.com/preview/14610589/BW0422.html

Positron Tracks [ circles (actually spirals) ]
http://images.sciencesource.com/preview/11976363/9G4128.html

[FusedTrinity]

I know this post is late but I know what the cause of this phenomena is. I have worked with cloud chambers for quite a while and observe this often. It occurs when a drop of liquid alcohol drips from the top of your cloud chamber. When it hits the bottom plate it changes temperature extremely quickly which cause an instant condensing effect. This is why you can see the two small orbs around the edge from the splash.

[Matildasmith]

That photo is gross man....i hate to see that man with all those pimples and all,,they have actually all burst out of his skin which makes it look even more worse..

[puerile]

Hi! I think that's an explosion of electrons:

[chris]

Nice video; lovely effects; you can watch that all day and not get bored. Totally fascinating.