THE DIFFUSION OF A HIGHLY IONIZED PLASMA ACROSS A MAGNETIC FIELD

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Abstract
The decay of electron density and temperature has been measured in a low-pressure helium afterglow by means of double floating probes of very small collection area. The plasma was contained in a glass toroidal chamber; initial gas pressures were in the vicinity of 0.030 Torr. Magnetic confining fields from 0.004 to 0.0860 Wb/m2 were used and the degree of ionization was such that coulomb collisions were dominant. Strict criteria were adopted to ensure reliable operation of the double probes. A theory of diffusion is presented which includes interactions between all species of particles. Drift effects due to the inhomogeneous magnetic field are important at the higher field strengths and are taken into account. Reasonably good agreement is found between the theoretical and observed time constants for electron-density decay over a wide range of experimental conditions.