New Inductively Heated Plasma Source for Reentry Simulations

Abstract

Apart from magnetoplasmadynamic plasma generators (MPG) and thermal arcjet devices (TPG) for re-entry simulation, inductively heated plasma generators (IPG ) have been developed for basic TPS material tests at the IRS. These inductively heated plasma generators consist mainly of a water-cooled coil surrounding a tube in which the plasma is located Due to this setup no electrode erosion appears; impurities in the plasma are minimized. Hence, both the behaviour of the gas components can be examined singularly and basic material tests such as the determination of the catalytic behaviour can be performed. With IPG3 an rf-source is provided where the coil is closer to the plasma than it was with previous designs. Therefore, the electromagnetic field loss is reduced. The water cooling system surrounds both the induction coil and the plasma container. IPG3 was qualified up to an anode power of 180 kW (argon), which is an essential improvement regarding the intended re-entry simulations in combination with the IRS MPG-simulations in the plasma wind tunnels 1 and 2 (PWK). The structure of the rf-plasma source IPG3 and the facility PWK3 are presented in this paper. This paper describes the design of IPG3 and the first experimental results for the plasma source. Power characteristics of IPG3, which were measured under variation of gas, are shown. Within this variation of gas frequency measurements were made, which will be a help for later numerical simulations of IPG3. A CID camera was used to measure the radial intensity of the plasma through an axial optical window of IPG3. The results led to a rough determination of the skin depth for the operation with air.