FlareLab: Short time-scale diagnostics for rapidly moving magnetic flux tubes

Experiment The FlareLab experiment is a pulsed-power discharge designed to study the behaviour of plasma-filled arch-shaped flux tubes. Thereby, the experiment tries to mimic the dynamical behaviour of Solar prominences. Presently, the experiment is based on a theoretical model by Titov and Démoulin [1] and in its first version on a scheme proposed and operated by P. Bellan et. al. [2]. The experimental set-up is shown in figure 1a. By means of a fast gas valve a small amount of gas is puffed into the chamber directly in front of the electrode system. The two gas clouds merge and produce an ignition condition according to Paschen’s law. After a typical time delay of 1 ms to 6 ms the gas is ignited through a 1 kJ capacitor bank. The plasma ignition follows along an initially loop-shaped magnetic guiding field which forces the discharge into a semicircular shape. This magnetic field is produced by a pulse forming network connected to a line conductor underneath the electrode plane. After ignition the plasma pinches along the magnetic axis. For a more detailed description of the experiment see [3] and [4]. To illustrate the evolution of the discharge, images taken in subsequent shots by means of an intensified CCD camera are shown in figure 1b. During the first microsecond the arch collimates and then starts to expand into the vacuum chamber on a μs time-scale. Several μs after ignition the arch detaches from the electrode system and continues its expansion into the chamber. In figure 1b it can be seen that the apex height of the arch rises at a constant rate even after the detachment.