  The three-dimensional particle-in-cell model NAM-ECRIS is used for
investigation of how the DECRIS-PM Electron Cyclotron Resonance Ion Source is
reacting to changes in the source magnetic configuration. The accent is made on
changes in the magnetic field at the magnetic trap center, the minimum-B value.
It is calculated that the optimal normalized value of the field is ~0.8, close
to the experimental observations. The reasons for existence of the optimum are
discussed. It is observed that the electron energies are increasing with the
increased minimum-B values due to enhanced confinement of the energetic
electrons in the plasma. Bumps in energy spectra of the radially lost electrons
are observed and explained to be due to nonadiabatic losses of electrons.
