Characteristics of the plasma injected into D.E.C.A. 2

Deuterium plasma is injected from an electrode-less plasma gun along the lines of force of a static magnetic field. This field is constant over length of 1 m; it increases thereafter in a 10 to 1 ratio over a 4 meter length up to the chamber where the measurements are carried out. Density measurements are performed using Faraday cups and an 8.6 mm microwave interferometer. For instance in a 1600 G magnetic field a 0.5 x 1013 deutons/cm3 density arises for a plasma with velocity 3 x 107 cm/s. The transverse energy is first determined from the diamagnetic signal amplitude of magnetic loops. The main results are obtained from the study of plasma transmitted through a magnetic barrier by means of measurements made with a Faraday cup, magnetic loops and thermocouples. The results given by these different methods are in good agreement and allow to define for the whole of the plasma flow a mean < θ > value for the ions pitch angle. In a 1600 G, < θ > equal 32 degrees; i.e. mean transverse energy of 360 eV for a plasma with a 030 eV longitudinal energy (a velocity equal to 3 x 107 cm/s). The high value of the transverse energy might be attributed to a pre-compression in the field gradient. Preliminary measurements seem to indicate the possibility of trapping the plasma between two magnetic barriers. (authors)