Ceramic arc tube with internal ridge

A discharge lamp comprising an outer envelope, a lamp base, and a lamp stem, the outer envelope being sealed to the lamp stem and containing a ceramic arc tube, the lamp base having leadwires attached thereto and being connectable to an external source of electrical power, the leadwires passing through and being sealed to the lamp stem in order to supply electrical power to the arc tube from the external source;

• and
• the ceramic arc tube having an axially symmetric body enclosing a discharge chamber, the body having a lower end well and opposed electrode-receiving members extending outwardly from the body along the symmetry axis, each electrode-receiving member having an electrode assembly passing therethrough and being sealed to the electrode-receiving member with a frit material, a proximal end of the electrode assemblies extending into the discharge chamber, a distal end of the electrode assemblies being connectable to the electrical power supplied by the leadwires, the discharge chamber containing a metal halide fill and a buffer gas, the lower end well having a curved wall and a circumferential ridge protruding from the curved wall into the discharge chamber.

A metal halide discharge lamp comprising a sealed outer envelope containing a ceramic arc tube, the ceramic arc tube having a body enclosing a discharge chamber, the body having a lower end well and opposed electrode-receiving members extending outwardly from the body, each electrode-receiving member having an electrode assembly passing therethrough and being sealed to the electrode-receiving member, the electrode assemblies being connectable to an external source of electrical power, the discharge chamber containing a metal halide fill, the lower end well having a curved wall and a circumferential ridge protruding from the curved wall into the discharge chamber.

The lamp of claim 19 wherein the metal halide salts are substantially constrained in the lower end well during lamp operation.