Effects of ambipolar potential in a two-component gasdynamic confinement system

Ambipolar effects stemming from the presence of a peak in the density of fast electrons can influence the velocity at which cold plasma flows out of a gasdynamic confinement system containing a two-component plasma is studied. There are two very different limits of this outflow. In the first, the density of fast particles at the peak, n(/sub T/, is lower than the density (n/sub D/0) of the bulk plasma in the uniform region. In the second case, the opposite relation holds. In the first case, the loss rate is found from the solution of the problem of the gas flow from a Laval nozzle. Depending on the value of N(/sub T/, the sonic point is either at the location of the maximum mirror ratio or at the peak in the fast-particle density. If N(/sub T/ varies smoothly, the position of the point at which the velocity of sound is crossed changes abruptly, and there are also abrupt changes in all the spatial characteristics of the flow. In the second case, the loss rate is determined by a method similar to that used for tandem mirrors with a short mean free path. A distinctive feature of this problem is that, because of the low ion temperature of the bulk plasma, a pronounced ambipolar-plugging effect is possible even if N(/sub T/ is only slightly greater than n/sub D/0