Plasma Confinement by Means of a Rotating Magnetic Field; OPSLUITING VAN PLASMA MET BEHULP VAN EEN DRAAIEND MAGNEETVELD
The field and density distributions in the boundary layer of an alternating pinch plasma were calculated for large and small values of nu / omega , where nu /sub c/ is the electron-ion collision frequency and omega is the frequency of the applied field. If nu /sub c/ >> omega , shear is produced in the magnetic lines of force in the skin. For a plasma column in equilibrium, the calculated field distribution satisfies, under certain conditions, the stability criterion of Suydam. From this result a number of requirements for alternating pinches can be derived. The validity' of the theory is discussed, and the equilibrium of an alternating pinch in toroidal geometry is calculated. Experiments were carried out in a torus covered with a metal shell. Around the torus two helical coils were wound, through which damped alternating currents at about 80 kc/ sec passed. Depending on the phase shift between these currents a z- pinch, a theta -pinch or an alternating pinch was produced. The mutual inductance of the two helical coils, in the presence of a discharge, should be low. In the experimental arrangement, the derived stability requirements were not met. Therefore, the formation of the column was primarily studied. As a result of the initial conditions, caused by the use of the helical coils, a wide column with a large trapped field was produced, which inhibits a comparison between theory and experiment. In a second arrangement the theoretical requirements can be fulfilled. Furthermore, a set of orthogonal coils'' is used. Now in the initial phase, before the field starts to rotate, a theta - pinch is produced. This first stage of the alternating pinch is extensively studied (in H/sub 2/ and He, with and without a predischarge). The temperature of the plasma is derived from the outward directed acceleration of the column in the inhomogeneous B/sub z/-field and from measurements of relative intensities of spectral lines in He. The mass of the plasma is obtained from the period of the radial oscillations of the column. In He all the gas is trapped in the pinch; in H/sub 2/ the measurements indicate an incomplete trapping. However microwave measurements show that even in H/sub 2/ the electron density outside the column is low (<10/sub 20//m/sup 3/). Measurements on the (unstable) z-pinch are described. If only one of the helical coils is energized a screw pinch is produced. During the first haif period (6 mu sec) this pinch, according to magnetic probe measurements and streakpictures, is in equilibrium and completely reproducible. The drift of a plasma in a curved magnetic field is analyzed. The calculation of the outward bound acceleration is valid for arbitrary values of BETA and for an arbitrary density distribution in the column. (auth)
- Research Organization:
- Stichting Voor Fundamenteel Onderzoek der Materie. Instituut Voor Plasma-Fysica, Jutphaas, Netherlands
- NSA Number:
- NSA-18-015336
- OSTI ID:
- 4073350
- Report Number(s):
- NP-13631
- Country of Publication:
- Country unknown/Code not available
- Language:
- English
Similar Records
STABILIZED PINCH CONFIGURATIONS
CONTROLLED NUCLEAR FUSION REACTOR