Metal vapor discharged lamp with specific angle between electrodes and tapered envelope wall

A metal vapor discharge lamp comprising:

• a discharge tube comprising a container made of ceramic, said container having
• a first cylindrical portion;
• second cylindrical portions with an outer diameter that is smaller than an inner diameter of said first cylindrical portion;
• third cylindrical portions with an outer diameter that is substantially the same as an inner diameter of said second cylindrical portion, tapered portions having an inner surface;
• and containing a discharge metal compound sealed into said container;
• and
• a pair of electrodes having first ends and second ends arranged in said container;
• wherein said first cylindrical portion, said tapered portions and said second cylindrical portions are formed in one piece;
• each of said third cylindrical portions is attached to one of said second cylindrical portions;
• the first ends of said pair of electrodes oppose each other inside the container;
• the second ends of said pair of electrodes are attached and sealed into the third cylindrical portions using a sealing member;
• an inner wall of said third cylindrical portions and said electrodes define a gap;
• and
• the inner surface of said tapered portions and a central axis of said electrodes define an angle of 40°-80°.