Measurement of the muzzle dynamic pressure of the plasma dynamic accelerator

The plasma dynamic accelerator comprises a coaxial railgun-like first stage that accelerates a plasma to very high velocities. The second stage, the compressor coil, compresses this plasma into a fast and dense plasma flow. A series of experiments was conducted to measure the dynamic pressure in front of the muzzle. Kistler Type 6157 BA pressure probes served as pressure gauges. The evaluation of these measurements was assisted by measurement of the current in the coil ground loop, the inductance of the system and by high speed photography three different coil shapes were used to evaluate the influence of the coil shape on the compression. A non-conducting coil with a shape identical to one of these coils was tested to determine the contribution of aerodynamic forces to the plasma compression. Additional tests were performed with a non-conducting conical tube to see whether a coil has aerodynamic benefits compared to closed contour. Finally, the coil was completely omitted. Only the coil holder, attached to the ground loop, remained in the system. This configuration forced a mainly axial discharge from the tip of the coaxial accelerator's center electrode to the holder and allowed the investigation of the contribution of the z-pinch to compression. This paper describes the configurations used in these experiments and presents the results of the measurements. These results are compared to each other and conclusions are drawn on how to improve the coil.