NONLINEAR-INTERACTIONS BETWEEN HIGH HEAT-FLUX PLASMA AND ELECTRON-EMISSIVE HOT MATERIAL SURFACE

Nonlinear dynamic behaviors are investigated for a system composed of high heat Aux plasma and electron-emissive hot material surface. Phase transitions due to bifurcation have been observed in the experiments and analyzed numerically by using a series of simple equations describ ing energy balance as well as sheath formation, including a new Child- Langmuir expression for an electron emission from the material surface into the plasma. It is found that the thermal insulation between thes e two constituent parts depends not only on plasma parameters but also strongly on electron-emission characteristics of the material surface in a nonlinear way. The electron emission leads to a strong reduction of sheath voltage and a large enhancement of heat flux density on the material surface. The plasma is cooled when it is in contact with a s trongly electron-emissive material surface. (C) 1996 American Institut e of Physics.