  Based on the Boltzmann-Uehling-Uhlenbeck (BUU) transport model coupled with a
phase-space coalescence afterburner, spallation reaction of $p+^{197}Au$ at the
incident beam energy of E$_{beam}$= 800 MeV/nucleon is studied. We find that
the number of test particles per nucleon has minor effects on the neutron to
proton ratio (n/p) of the produced heavier fragments while it affects much on
their yields. The external strong magnetic field affects the production of
heavier fragments much than the n/p of produced fragments. The n/p of free
nucleons is greatly affected by the strong magnetic field, especially for the
nucleons with lower energies.
