From: dietz@dls.net   
      
   Mike Miller wrote:   
      
   > Do you mean photons or protons cause cascades? I know protons do.   
   > They're being looked at as sources of spallation neutrons in some   
   > "waste burning" nuclear reactors. But photons?   
      
   Photons produce an electromagnetic cascade by pair production   
   and bremsstrahlung.  There are also photonuclear reactions, but   
   these are relatively less important.   
      
   Photons do not make up much of the cosmic ray load, though.   
      
   	Paul   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)