Hello all, i am having a few problems simulating cosmic rays with a silicon CCD detector, mainly because my knowledge on particle physics is quite poor. I am simulating primary cosmic rays, which predominantly consist of single protons and alpha particles. I am treating the protons as minimum ionizing particles, since the kinetic energy of cosmic ray protons are between 10^9 eV and 10^20 eV. I tried to use the Bethe-Bloch equation to determine the minimum ionisation energy but failed miserably. However, from some online searching, i found that minimum ionizing particles lose 1.66 MeV cm^2/g of energy when travelling through silicon. My first question, am i correct to treat the cosmic ray protons as minimum ionizing particles? Secondly, can i also treat the alpha particles as minimum ionizing particles? I have read the alpha particles do not penetrate matter very well. So confused !!! Any help is appreciated, thanks. Cheers.