  A new 3 dimensional Particle-in-Cell code was applied to simulate the
operation of a 100 W CHT thruster. In the simulation a spoke moving with a
velocity of about 0.8 cm/\mu s was observed. The initial position of the spoke
was found to be strongly correlated with the cathode placement. The simulation
has shown that the depletion of neutral gas can lead to azimuthal asymmetry of
the discharge and possibly to the spoke phenomenon.
