Temperature diagnostics in a high-pressure hydrogen microwave plasma torch I: experimental characterization

We present preliminary results of an experimental study of a hydrogen plasma flame produced using a microwave axial injection torch (torche à injection axiale or TIA). This device usually runs in argon or helium at atmospheric pressure providing a stable discharge at high HF power levels and a two-temperature plasma. In the current work, hydrogen plasma is launched in a helium filled chamber to prevent hydrogen-air explosive reactions. Seven spectroscopic hydrogen lines have been detected in the visible spectrum (the Balmer series of hydrogen). Using a Boltzmannplot representation it is shown that the plasma is far from equilibrium, but the electron temperature still can be obtained from a modified plot via a p^−x-correction, which shows that the lower energy levels of Balmer series of the hydrogen system is ruled by the excitation-saturation balance (ESB).