A Phywe PJ45 cloud chamber was temporarily put in the Pic du Midi (French observatory in the Pyrenees) in 2012 for the 100th anniversary of the discovery of cosmic ray.
The video show a complete recording of 11 minutes, taken with my HD camera and a polarizing filter. As expected at this altitude, we see many more protons than in sea level (about 10 times more). They come from spallation of cosmic particles (p,n) in the wall of the chamber, or from the nuclei (oxygen, nitrogen...) inside the chamber. Dimension of the surface of the machine is 45x45 cm.
See the website http://www.cloudylabs.fr for more pictures and commentary about theses nuclear events.