부산대학교 도서관

In high current z-pinches, it is a challenge to measure the current flow profile in the plasma sheath. A Laser Wavefront Analyzer (LWA) combined with laser polarimetry is used to make spatially- and temporally- resolved measurements of the plasma density and magnetic field profiles in gas puff z-pinches. Experiments are conducted on the 1 MA COBRA at Cornell. The LWA works by directing a ~100 ps, polarized laser beam across the imploding z-pinch plasma. After the plasma, a ~100x100 microlens array focuses the laser beam into a large number of very tiny spots. The image of the spots is then separated in the horizontal and vertical polarization state when passing a polarization splitter cube. The resulting two polarization images are captured with CCD cameras. By taking the images with and without a current carrying plasma, relative position and polarization (due to Faraday rotation) changes of the microlens focal spots are measured, from which the plasma densities and magnetic field are derived. Multi-frame visible and XUV framing cameras, laser shearing interferometer, radially-resolved Thomson scattering and visible light plasma spectroscopy are also used to characterize the implosion. From these, the imploding plasma density, temperature and velocity are also inferred. Details of the experiments will be presented.