Cosmic rays (CRs) with energies below the 'knee' at about 3 PeV are believed to be of Galactic origin, but it is still not fully understood in which astrophysical objects they are produced. The classical paradigm states that Supernova remnants (SNRs) are the main sources of Galactic CRs
mainly on the account of their energy budget that is sufficient to explain the energy density of low-energy CRs. But whether SNRs are responsible for all the Galactic CRs or not, depends on the answers two three fundamental questions:
1) Are SNRs capable of accelerating protons up to PeV energies?
2) Can SNRs explain the elemental composition observed in CRs?
3) Can SNRs supply the correct shape of the production spectrum of CRs?
