In a D-3He fusion reactor, direct energy conversion is expected, and discrimination of charged particles from each other is needed to produce electric power. The authors have performed simulation experiments for discrimination and direct energy conversion in a CUSPDEC device with a slanted cusp magnetic field. This paper presents a scaling of particle discrimination with proposition of an appropriate scaling factor based on the consideration of the Störmer potential. Experimental results with the factor up to 0.7 for ions and 80 for electrons are presented. The paper also presents results of direct energy conversion of ions in higher energy region up to 5 keV. It is confirmed that the conversion efficiency does not depend on averaged energy, but depends on the broadness of energy distribution function.