Two-temperature, two-dimensional modeling of cathode hot spot formation including sheath effects-application to high pressure xenon arc lamps

Summary form only given. One of the fundamental problems in high pressure gas discharges is the prediction of plasma/cathode interaction. The cathode hot spot temperature determines electron emission and plasma formation. The critical physical processes in the cathode/plasma system are electron emission, heat conduction and the formation of the cathodic boundary layers and the thermal plasma expansion zone. The nonlinear interaction of these phenomena is decisive for important technological parameters like electrode erosion and peak plasma temperature, e.g. in HID-lamps. The self consistent single temperature model is extended to allow for deviations of electron temperature T/sub e/ from heavy particles temperature T/sub h/. Modeling of the cathode-plasma region now includes the following physical processes self consistently: heat conduction within the cathode body (2-D); electron emission of the surface (T, TF, ...,); space charge layer formation (sheath); diffusion and ionizational non-equilibrium within a thin skin layer (presheath); current and heat transport in the cathodic plasma, without the LTE assumption (2-D). Assuming a stationary discharge in cylindrical symmetry, the model is applied to high pressure xenon short arc lamps with operating pressures of 1-4 MPa and currents of several ampere. The temperature split region is found to extend over 200 /spl mu/m in front of the cathode surface. Sheath effects critically influence the hot spot temperature of the cathode.