Diagnostics by electron beam fluorescence in hypersonics

Electron beam fluorescence is a well established technique to perform local and non intrusive measurements of density, vibrational and rotational temperatures and velocity in a low density flow of nitrogen or air (⩽10¹⁶ molecules.cm^-3). This paper describes two recent applications (flow visualization and velocimetry) in low density hypersonic wind tunnels using a multi-purpose electron gun. Flow visualization, obtained by sweeping the electron beam to illuminate a sheet in the flow, is useful to follow density variations and expose shock waves. It is here applied to study interferences between shock waves issued from two models placed in a Mach 10 flow. Velocity measurements have also been carried out by using a pulsed electron beam to tag a flow with afterglowing plasma columns for optical time of flight detection