Patent ID: 8791635

Claim:
A short arc discharge lamp, comprising: a light emitting tube; and a cathode electrode and an anode electrode disposed opposite to each other in the light emitting tube, the cathode electrode comprising a body part made of tungsten and a tip part made of thoriated tungsten, the body part and the tip part being solid-phase bonded to each other, wherein, on a section of the cathode electrode taken along a line perpendicular to a junction interface between the body part and the tip part, in an arbitrary portion of 500 μm or more in length along the junction interface, when a length of the arbitrary portion along the junction interface is set to L 0 , and a sum of lengths of tungsten crystal grains, along the junction interface, that are present through the junction interface is set to L, (L/L 0 )≧0.16 is satisfied.