Experiments on the magnetic compression of a plasma are being carried out in many laboratories, largely because of the possible ultimate application as a fusion reactor. The theory of the rapid compression of a pinched gas discharge has been discussed by several authors. The collapse time of a simple pinched discharge is determined essentially by the inertia of the ionised gas, as shown by Leontovich and Oso vets.
We have used a quartz tube 10.8 cm long, 2.8 cm in internal diameter and 1 mm in wall thickness and produced the pinch effect by current in an axial direction in pre-ionized plasma. Before the gas was ionized, a magnetic field in the axial direction was produced by external coils. The following magnitudes are typical: duration of pulse, 25 mμsec; potential difference between the electrodes, 20 kV; current through the tube, 30 kA; gas pressure before ionization 50 mtorr. Measurements were made of the potential difference between the electrodes, the current through the tube and the magnetic field within the tube in both the θ and z directions. It was found that the current skin thickness (3—4 mm) was much larger than any existing theory predicts. A theory based on the assumption that the drift velocity of the electrons is limited by “streaming” instabilities is developed. This theory explains most although not all of the experimental results.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.