Dr. John Armitage

Professor Emeritus
3360 HP
(613) 520 - 2600 Ext. 4326
armitageatphysics [dot] carleton [dot] ca


Cosmic Rays: Physics and Applications

Cosmic Rays: physics and applications

The earth is bathed in an almost continuous flow of particles - historically called ‘rays’, whose origins are the sun, the stars and violent supernovas occurring somewhere in the galaxy. These galactic and solar cosmic rays are predominantly protons which, after deflection by the Earth’s magnetosphere, interact in the upper atmosphere producing showers of lighter secondary particles. On the surface of the Earth we detect the more penetrating secondaries – typically muons.

Some information about their creation and their subsequent travel to the Earth can be gleaned from a record of the muon intensities and possibly angular distributions. In particular the presence of a major solar storm: a coronal mass ejection (CME) , modifies and changes the flux we detect, so it may be possible to use that record to predict the arrival of the storm. These on-going investigations started with FOREWARN.

The penetrating property of muons can be exploited for practical purposes. Muons, with energies in the middle of the spectrum observed at ground level, can penetrate more than a metre of steel. This is to be contrasted with high energy gamma rays, from a cobalt 60 radioactive source for example, which are absorbed in several centimetres of steel. Muons are therefore very useful for inspecting cargo – particularly cargo which may be suspected of containing illegal high Z material. This is being investigated in the CRIPT experiment.