Macroscopic Transport Properties of a Fully Ionized Alkali-Metal Plasma

The one dimensional, macroscopic transport equations are solved for the special case of a fully ionized potassium plasma generated in the Q-device, and the solution is used to predict the volt-ampere characteristic. Agreement between predicted and measured volt-ampere characteristics is very good at low currents but not as good at high currents. The disparity is believed to be due to the presence of large potential and thermal gradients in front of the hot plates at high currents, which are predicted by the theory when the thermoelectric coefficients are taken into account. The average experimentally determined electrical conductivity is 1.2 times the Spitzer-Härm value with an rms error of about 10%. The average experimentally determined thermal conductivity is 0.98 times their value with an rms error of about 10%. A criterion is established for determining when the sheaths in front of the plates do not affect the volt-ampere characteristic, and for determining when the plasma is truly collision-dominated. The axial variations of temperature and potential are also determined. A sudden change in the volt-ampere characteristic that coincides with the onset of instabilities in the plasma is not explained by the theory or by a simple interpretation of the sheath properties. The value of lnΛ was assumed to have a constant value of 7.