Ultraviolet tomography of kink dynamics in a magnetoplasmadynamic thruster

We present the results of a project concerning the ultraviolet (UV) imaging of a plasma for space applications, produced in a magneto-plasmadynamic (MPD) thruster. MPD are a class of high power electric space propulsion devices that accelerate a plasma to high velocities ($>$10 km/s), by exploiting the Lorentz force between the discharge electrical current and a self induced and externally applied magnetic field. The imaging system has been realized by inserting 3 arrays of UV-enhanced photodiodes (with built-in amplifiers) directly into the plastic structure of the anode. This advanced diagnostic design allows for a detailed tomographic reconstruction of the emissivity spatial structure, both in the axial direction z (corresponding to a wavenumber n) and azimuthal direction (wavenumber m) with high time resolution. A magneto-hydrodynamic (MHD) instability, with mode numbers m=1 and n=1 has been observed, which might affect the performances of the thruster.