Initial development of hybrid plasma jet generator of O 2 (1Δ) for DOIL

Abstract

The initial stage in development of hybrid plasma jet generator of singlet oxygen O₂(¹Δ) for a discharge oxygen-iodine laser (DOIL) is presented. This novel type of generator is based on a fast mixing of hybrid argon plasma jet of DC electric arc and RF discharge with a neutral molecular oxygen stream. Arc plasma jets have a much higher density of electrons than RF plasma jets to compensate the electro-negativity of oxygen and they can be operated at a higher pressure for an efficient supersonic expansion cooling in DOIL. An RF discharge is applied to the DC arc plasma jet at the hollow anode of the plasmatron to switch it from a hot-spot mode to a diffusive mode. That is advantageous with the use of aluminum anode, which has a lower melting point and a significantly lower rate of O₂(¹Δ) quenching compared to a standard copper anode in a gas plasmatron. An enhanced non-equilibrium in the plasma jet caused by the RF discharge and neutral oxygen injection is desirable for an efficient O₂(¹Δ) generation. Preliminary calculations on the equilibrium composition of O₂-Ar mixture suggest keeping the arc temperature well down to prevent an excessive dissociation of the molecular oxygen.