Experimental investigations on a toroidal screw pinch
High-β Deuterium plasmas in a temperature range of 0.1–1 keV were produced in the fast toroidal screw pinch experiment ISAR IV (Bmax≈33 kG,Iz max≈100–150 kA, coil diameter 12 cm, aspect ratio 5). The experimentally determined growth rates of the appearing instabilities—especially them=1 mode—are compared with two simple models and a more exact numerical calculation. This comparison and direct measurements of the magnetic field distribution show that the constant pitch model of Bobeldijk1 is a suitable first approximation for the normal screw pinch. Using a delay of thez and θ-bank as a first simple method of field programming this constant pitch profil could be varied in different directions. The results are discussed in more detail and confirm the theoretical picture of stability behaviour of the high-β screw pinch.