Characterisation of Argon flows in the arc heated facility L2K using Diode Laser Absorption spectroscopy and additional optical diagnostics

Abstract

Argon flows in the arc heated facility were studied with the aim to reduce thermal loads of reentry vehicles using MHD effects and to study a new mitigation scheme for re-entry blackout via numerical and experimental methods in order to demonstrate the possibilities to solve the radio blackout problem using a MHD effect. Argon flows are used because compared to air flows relative high electron and ion densities can be realized in ground based facilities with long constant flow duration. In addition the small number of chemical reactions in high enthalpy Argon flows simplifies the numerical simulation of MHD effects. Different optical diagnostic techniques are used to study the physical properties of Argon flows. Diode Laser Absorption Spectroscopy, Laser Induced Fluorescence spectroscopy, Optical Emission Spectroscopy, Fourier Transform Infrared Radiation emission spectroscopy and MicroWave Interferometry were applied to Argon flows in the L2K facility. The electron density, the number of ions and neutrals, the velocity and temperature were measured in the free stream and in vicinity of a cylindrical model placed in the flow. The advantages and disadvantages and the results from the different measurement techniques are discussed and are compared.