A short arc lamp comprises front and back subassemblies including mating weld rings, whereby the lamp can be assembled and sealed through welding of the weld rings. Each subassembly includes a number of self-aligning components to facilitate assembly and improve alignment accuracy. The metal body of the lamp can have a cooling projection portion, which can be received by a heat sink to remove heat from near the anode. A heat sink also can be formed as part of the metal body. The lamp reflector can be a drop-in reflector, or can be formed as part of the metal body through a process such as metal injection molding. A single strut can be used to position the cathode, which can be part of the sleeve or received by a portion of the sleeve. A trigger electrode can be used to simplify the power supply for the lamp.