3D modeling for HID lamp cathodes

Summary form only given, as follows. The lifetime and the wall blackening of the high intensity discharge (HID) and high pressure sodium (HPS) lamps are strongly related to the electrode temperature, type of arc burning and to the discharge ignition. At the same electric voltage drop and current discharge, two type of cathode operating mode exist. Recently, super-spot and spectroscopic blue-core modes of the cathode arc attachment were experimentally observed. The diffuse mode functioning of the cathode is favored by a high discharge current value, by a weak cooling of the electrode and by low-pressure. In the contrary case, the hot-spot mode is favored. In this presentation we describe a 3D model able to obtain the temperature distribution in the bulk of an HID and HPS lamp electrode when this is operate either diffuse or hot-spot modes.