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2 2016

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Experiments and simulations on the possibility of radiative contraction/collapse in the PF-1000 plasma focus

Akel M., Cikhardt J., Kubes P., Kunze H.-J., Lee S., Paduch M., Saw S. H.

Nukleonika

2016

Vol. 61, No. 2

145--148

Experimental studies of discharges in the plasma focus facility with neon filling and respective numerical simulations employing the radiative Lee code are reported. The pinch currents exceed the Pease-Braginskii current, which indicates that radiative losses are larger than heating and that contraction of the formed plasma should occur. Both of these effects were indeed observed. Parallel numerical simulations were crucial for the identifi cation of such an effect.

Evolution of the small ball-like structures in the plasma focus discharge

Cikhardtova B., Kubes P., Cikhardt J., Paduch M., Zielinska E., Kravarik J., Rezac K., Kortanek J.

Nukleonika

2016

Vol. 61, No. 2

155--159

The experiments were carried out in the PF-1000 plasma-focus device at the maximum current reaching about 2 MA, at the deuterium or neon filling and with deuterium injected from a gas-puff nozzle placed on the axis of the anode face. Ball-like structures of diameters of 1–12 mm were identifi ed in interferometric and XUV pinhole camera frames. We made the statistical description of their parameters. A lifetime of the ball- -like structures was in the range from 30 to 210 ns, and in some cases even more. These structures appeared mostly at the surface of the imploding plasma shell and they did not change their position in relation to the anode end. During the evolution of these structures, interferometric fringes were observed near the surfaces of the structures only, and their internal parts were initially chaotic (without noticeable) fringes. Subsequently the number of interferometric fringes increased (the internal ‘chaotic’ area was fi lled with fringes too) and later on it decreased. The radii of the ball-like structures were mostly increasing during their existence. The maximum electron density reached the value of 1024 to 1025 m–3. The ball-like structures decayed by absorption inside the expanded pinch column and/or gradually expired in rare plasma outside of the dense plasma column.