Enthalpy probe measurements were taken of the converging plasma plume in a triple torch plasma reactor and related to substrate heat flux measurements. Results show excellent entrainment of process gases injected into the converging plasma plume by way of the central injection probe. At lower pressures (less than or equal to 40 kPa), the plasma volume is equivalent to at least a 3 cm diameter, 4 cm long cylinder, M with relatively uniform temperature, velocity and substrate heat flux profiles when compared to a typical de are jet. Converging plasma plume sii-e, substrate heat flux and enthalpy profiles are also shown to be a strong function of applied system power. Substrate heat pier measurements shoe smaller radial gradients than enthalpy probe measurements, because of the high radial velocity component of gases above the substrate boundary layer. Enthalpy probe measurements Ir ere also conducted for diamond deposition conditions and approximate temperature and velocity profiles obtained. Problems with the uniform gas mixture assumption prohibited more accurate measurements. Reproducibility of enthalpy measurement results was shown with an average standard deviation of 11.8% for the velocity and 7.6% for the temperature measurements.