Metal vapor discharge lamp having cermet lead-in with improved luminous efficiency and flux rise time

A metal vapor discharge lamp having an arc tube comprising:

• a discharge portion composed of translucent ceramic in which a discharge metal is filled and a pair of electrodes is disposed;
• small tubular portions composed of ceramic coupled to both ends of said discharge portion, the surfaces including the respective end faces of the small tubular portions defining a discharge space in cooperation with the inner surface of said discharge portion;
• feeder bodies composed of a conductive cermet inserted into said small tubular portions, the end portion of the feeder bodies being connected to respective said electrodes;
• and
• a sealing material of a glass frit for sealing the gap between said feeder body and said small tubular portion at the end portion opposite to said discharge space, wherein
• the ends of the conductive cermets and the end face of the glass frit on the discharge space side are recessed from the discharge space,
• the ends of the conductive cermets on the side opposite to said discharge space extend at least to the ends of said small tubular portions, and
• the temperature of the end face of said sealing material on the discharge space side during the lamp operation is not more than 800° C.