Earlier I said
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Not until you incorporate a mechanism which will prevent decay while the polonium is traveling through the crack. Otherwise the result of this scenario - which isn't observed - would be a tube shaped halo. Only spheres are found. You'll also need another mechanism to keep the polonium from exiting prior to decay. And you'll need your mechanism to operate quickly. Did you happen to notice the halflife you're dealing with?

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... Gases flow. A gas flowing through a crack isn't going to stop at a destination and decay when you wish. Some will decay on the way, some - most - will pass through & out the other side of the "collection point". There must be an exit, or the gas won't flow in to begin with. You need a valve & you need to time it somehow & you need to prevent decay everywhere except at the selected location.

Since there's no known way to prevent decay, gas flowing through the system must decay the entire time and the path must show as a tube around the path. Until your gurus concoct a way to prevent undesired decay, their fantasy is a joke.
It may be helpful to provide pictures to demonstrate this. I've found some.
<img src="http://home.hetnet.nl/~genesis/Gentry/Catalogus/Image77.jpg"><img src="http://home.hetnet.nl/~genesis/Gentry/Catalogus/Image72.jpg">
It is said that microscopic cracks could allow gases to flow to a collection point. These pictures are magnified, and some actually do appear to have cracks; but not all. The upper left radiohalo is the best I could find for the scenario imagined.

Even if one imagines radioactive gas flowing along this crack, there's still no reason for it to only decay at the collection point. It should decay the entire time, and leave a trail. There doesn't appear to be any valve mechanism either, so there's no reason for the gas to stop and decay at the collection point, rather than flowing right through.

While one can understand the process of concocting such a just-so story, I don't think one can accept it without first considering the clear implications and requirements. Time is also a factor, as I said before.

Pic source: http://home.hetnet.nl/~genesis/Gentry/Catalogus.htm

Dark Matter + Dark Energy = Dark Truth

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