  The ordinary-extraordinary-Bernstein (O-X-B) double conversion is considered
and simulated with a kinetic particle model vs full wave model for parameters
of the TJ-II stellarator. This simulation has been done with the
particle-in-cell code, XOOPIC (X11-based object-oriented particle-incell).
XOOPIC is able to model the non-monotonic density and magnetic profile of
TJ-II. The first step of conversion, O-X conversion, is observed clearly. By
applying some optimizations such as increasing the number of computational
particles in the region of the X-B conversion, the simulation of the second
step is also possible. By considering the electric and magnetic components of
launched and reflected waves, the O-mode wave and the X-mode wave can be easily
detected. Via considering the power of launched O-mode wave and converted
X-mode wave, the efficiency of O-X conversion for the best theoretical launch
angle is obtained, which is in good agreement with previous computed
efficiencies via full-wave simulations. For the optimum angle of 47? between
the wave-vector of the incident O-mode wave and the external magnetic field,
the conversion efficiency is 66%.
