Positron discovery in cloud chamber, how so?

[DaTario]

Hi All,

I was watching a video from Veritassium () when it was said that positron discovery was made in a cloud chamber. If the anti-particle of the electron is passing through a dense cloud of atoms and molecules, won't it be natural for this anti-particle to meet an electron and go through a fast pair anihilation, giving rise to photons?

Best wishes

DaTario

 

[DaTario]

Sorry, this question seems to have already been addressed in the thread "How Do Positrons Reach Cloud Chambers Without Annihilating?"

It has to do with the typical lifetime of the positron inside matter ($10^{-10}$ s).

 

[Vanadium 50]

https://www.aps.org/apsnews/2004/08/discovery-positron-1932

 

[Nik_2213]

IIRC, our school's cloud-chamber had an optional magnetic field via a pair of coils. Trails from the 'source' spiralled one way for electrons, other way for their anti-kin. And, if you were quick, measurement of curl's diameter allowed a useful estimate of energy etc...

Our school had a 'Treasure Trove' of Nuffield teaching equipment, akin to 1st-year Uni Physics level...