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

The possibility of radiative collapse in pinched linear discharges was fi rst studied independently by Pease [1] and Braginskii [2] in 1957 for pure hydrogen or deuterium plasmas. When radiation losses by bremsstrahlung exceed Ohmic heating at high currents, they predicted shrinking of the plasma column, which may even result in a collapse of the column to extremely high densities. They derived a critical current value that has to be exceeded. Originally calculated for homogeneous and infi nitely long plasmas, refi ned approaches considered later took into account, for example, density profi les, axial outfl ow of plasma [3], which occurs in all laboratory plasmas of fi nite length, anomalous resistivity, opacity, and coupling of the pinch formation into a realistic electrical circuit [4]. For the observation of the phenomenon, z-pinches were studied on the experimental side, also specifi cally the pinch plasmas formed from fi bers of frozen hydrogen or deuterium and driven by high-voltage pulse generators. No radiative collapse or at least contraction could be clearly identifi ed. This could be due to, for example, the formation of complex internal structures like magnetic fl ux loops and fi laments [5]. Only one group reports the attainment of the Pease-Braginskii current in an ultra-high-pressure discharge [6]. Linear pinch plasmas are also produced in discharges of the plasma focus type. Discharges with Experiments and simulations on the possibility of radiative contraction/collapse in the PF-1000 plasma focus Mohamad Akel, Jakub Cikhardt, Pavel Kubes, Hans-Joachim Kunze, Sing Lee, Marian Paduch, Sor Heoh Saw