  In this paper, we analyze the results of neutral-beam current drive (NBCD)
experiments, performed in the TJ-II stellarator, with the aim of validating the
theoretical predictions. Both parallel and anti-parallel injection with respect
to the magnetic field were explored using co (NBI1) and counter (NBI2) beams at
different injected beam power and plasma densities. The fast-ion current driven
by both beams was simulated with the Monte Carlo code ASCOT and the electron
response to the fast-ion current was calculated analytically using a model
valid for an arbitrary magnetic configuration and a low collisionality plasma.
The model reproduces with rather good agreement the toroidal current measured
in NBI2 plasmas while the current driven by NBI1 is less than half the
predicted one. Possible reasons for this discrepancy are discussed.
