1. The thin-wire probe boundary-layer profile measurements were performed independently of the flush probe measurements in order to ensure that the thin-wire probe data were not influenced by charged-particle migration to local currentcollecting flush probes. Except for distances very close to the plate surface, the profile measurements at the X = 4-5 in. and 9.5 in. stations were obtained using a rake containing three probes, spaced 1 inch apart. !n the larger Debye length region near the wall (y < 0,05 in.), however, only a single probe was swept from -5to +2V, relative to ground in the nitrogen plasmas, and from -4 to +4Vin argo in a
2. Fig. 6
3. The results of the above e:xperiments and analyses are shown in Figures 10 - 23. The results are as follows: a. Flat Platen, T Profiles. These are shown in Figures 10 - 12. The ne-profiles in the flat plate boundary layer clearly show viscous interaction effects at the 4,5 in. station both in nitrogen and in argon CxN24 to 13, XAr 13 to 44). These subsequently relax to flat plate boundary layer profiles at the 9,5 in. station. The T - profiles show significant departure from thermal equilibrium and remain relatively constant in the boundary layer. For nitrogen, T 2300-2800"K and for argon, T 1000-15oo•K. For argon, T decreases to 800°K,
4. c. Probe Size and Geometry Effects. Figures 18-21 show the probe area effect on the ion current density J. The latter increases as the probe size decreases in agreement with the observations of Tseng and Talbot,32·and Lederman and Avidor.13The former did their study in collisionless sheaths and plotted their results relative to a free-fall sheath thickness A rr co 314•For collisional thick