  The energy balance of a plasma holds fundamental information not only about
basic plasma physics, but it is also important for tailoring plasmas to
specific applications. Especially RF-driven atmospheric pressure plasma jets
(APPJs) operated in helium with oxygen admixture have high application
potential in industry and medicine. Many types of plasma jets have been studied
up to now, leading to the challenge how to compare results from various
sources. We have developed a method for measuring the power deposited in the
plasma as the parameter to compare different sources and gas mixtures with each
other. Furthermore, we studied energy transport as a function of this input
power and molecular gas admixture in a newly developed APPJ based on the
COST-reference jet with a capillary as a dielectric in between the electrodes.
The gas temperature, atomic oxygen density, ozone density and absolute emission
intensity in the visible wavelength range have been determined. Combining the
results gave an energy balance with most of the energy deposited into gas
heating. Production of final chemical products made up a small amount of the
deposited power while radiation was negligible for all combinations of external
parameters studied.
