  The principal objective of this work is to report on the power coupled to a
tungsten target in the Proto-MPEX device during oblique injection of a
microwave beam (< 70 kW at 28 GHz) into a high-power (~100 kW at 13.56 MHz)
over-dense (n_e>1E10^19 m^(-3)) deuterium helicon plasma column. The
experimental setup, electron heating system, electron heating scheme, and IR
thermographic diagnostic for quantifying the power transport is described in
detail. It is demonstrated that the power transported to the target can be
effectively controlled by adjusting the magnetic field profile. Using this
method, heat fluxes up to 22 MWm-2 and power transport efficiencies in the
range of 17-20% have been achieved using 70 kW of microwave power. It is
observed that most of the heat flux is confined to a narrow region at the
plasma periphery. Ray-tracing calculations are presented which indicate that
the power is coupled to the plasma electrons via an O-X-B mode conversion
process. Calculations indicate that the microwave power is absorbed in a single
pass at the plasma periphery via collisions and in the over-dense region via
2nd harmonic cyclotron resonance of the electron Bernstein wave. The impact of
these results is discussed in the context of MPEX.
