The use of plastic disks coated with a thin film ( ~1 µm) of Aluminium has been investigated as a control mechanism for the shockwave formed from a radial foil z-pinch in the presence of an ambient medium. Experiments were carried out on the MAGPIE (1:4MA, 250ns rise time) facility at Imperial College London. It has been found that plastic formers replicate the results seen in standard radial foil z-pinch configurations and dramatically increase the working pressure of the experimental setup. The configuration produces a strong radiative shockwave driven with constant velocity ( ≥ 25km/s) for long time ( ≥ 400ns) and spatial scales (cm). Through comparison with standard radial foil configuration results a new formation model for shockwaves from radial foil z-pinches is proposed. The model is found to be in good agreement with all experimental velocity and profile data. The model indicates a means to maximise the shockwave velocity and alter the profile. Investigation of the effect of ambient medium atomic mass on shockwave parameters was then undertaken using the plastic former configuration. Experimental results demonstrate scaling of shock compression opposite to that found in 1D radiation hydro-dynamic simulations. Evidence of a thermal instability in the post-shock cooling region is linked to a decrease in compression for higher atomic masses due to increased radiative cooling. Increases in post-shock temperature and ionization have been measured with decreased radial distance from a strongly cooling hydrodynamic jet. Regions of observed thermal instability for Xenon and Krypton agree with those expected from evaluation of theoretical cooling functions. The possibility of temporal oscillation of the shock velocity due to thermal instability is also investigated.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:576065 |
| Date | January 2013 |
| Creators | Skidmore, Jonathan William |
| Contributors | Lebedev, Sergey ; Bland, Simon |
| Publisher | Imperial College London |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://hdl.handle.net/10044/1/11693 |
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