Experimental Determination Of The Mass Density of a Plasma Arc Armature

A diagnostic technique for determining the mass density, and possibly the composition, of the plasma arc armature in the MIDI-3 free-running arc device is described. The plasma arc armature consists primarily of polyethylene, copper and aluminum, and reaches velocities in excess of 8 km/s. The technique utilizes a flash x-ray source to produce continuum x-rays over the range of 1.5 to 20 keV. The absorption as a function of wavelength by the copper and aluminum is obtained with an elliptically-focussing crystal spectrometer for the wavelength interval 2.0 to 3.5 Å using a LiF crystal.