A 10 GHz ECR ion source (PK-GANESA) with a new magnetic field topology was developed in a GANIL-Pantechnik collaboration. The performance of this source is analyzed through simulations of electron trajectories over a time of $20\mathrm{\mu }\mathrm{s}$ to ensure both rf-heating and magnetic confinement, using the code trapcad. The electron energy distribution functions obtained from the simulations are characterized with respect to radio frequency, heating power, and simulation time. The results are compared with a more traditional 10 GHz ECR source (NANOGANIII) presently used at GANIL. Our study demonstrates an improvement of electron confinement (a factor 10 increase) with increasing rf heating power which should in principle lead to the production of highly charged ions, at variance with the measured production of high-charge-state ions, significantly lower than for the NANOGANIII source. A tentative explanation of the difference between both sources is discussed.