Abstract: A mandrel for use in a diamond deposition process for generating free standing diamond films has a segmented surface forming a plurality of surfaces for deposition of diamond. The segmented surface is formed of a plurality of mesa segments on a common supporting base surfaces for the mesas. The mesa segments are preferably removably attached to the common base by any suitable means such as by bolts through the mandrel substrate which extend into the mesa segments. The mesa segments may vary in shape, size, and number, thus permitting different shaped diamond films to be made simultaneously from the same run if desired. The provided arrangement increases yield by reducing losses due to premature lifting of the diamond film during deposition, due to violent lifting after deposition upon cooling of the mandrel, and due to cracking.

Abstract: A mandrel for use in a diamond deposition process for generating free standing diamond films has a segmented surface forming a plurality of surfaces for deposition of diamond. The segmented surface is formed of a plurality of mesa segments on a common supporting base surfaces for the mesas. The mesa segments are preferably removably attached to the common base by any suitable means such as by bolts through the mandrel substrate which extend into the mesa segments. The mesa segments may vary in shape, size, and number, thus permitting different shaped diamond films to be made simultaneously from the same run if desired. The provided arrangement increases yield by reducing losses due to premature lifting of the diamond film during deposition, due to violent lifting after deposition upon cooling of the mandrel, and due to cracking.

Abstract: An end plug for an arc tube for a high pressure discharge lamp is made by pressing alumina powder in a tapered cylindrical die so that the diameter of the as-pressed plug is greatest at that part of the plug that has the lowest as-pressed density. The variation in diameter of the as-pressed plug compensates for the variation in density so that upon high temperature sintering, the plug shrinks to a substantially uniform diameter.

Abstract: Sealing means for arc discharge tubes employ chamfers formed in the arc tube which mate with frusto-conical portions on sealing disks. Self-centering is thus provided as well as the elimination of one wire stop positioner for holding the sealing disks.

Abstract: An improved process for producing a translucent polycrystalline alumina body comprising rapid-sintering a prefired compacted green body of alumina of predetermined shape is disclosed. The green body of alumina includes alumina doped with one or more sintering aids. Rapid sintering in accordance with the method of the present invention comprises the steps of raising the temperature of the prefired compacted green body of predetermined shape up to maximum sintering temperature at a heating rate greater than or equal to about 0.1.degree. C./second and less than the rate at which the green body experiences thermal shock; and heating the green body at the maximum sintering temperature for a period of time sufficient to produce a translucent polycrystalline alumina body. The rapid sintering is carried out under a flowing gas mixture of nitrogen and at least about 2.5 volume percent hydrogen.

Abstract: An improved process for producing a translucent polycrystalline alumina body comprising sintering a prefired compacted green body of alumina of predetermined shape is disclosed. The green body of alumina includes alumina doped with one or more sintering aids. The method of the present invention comprises sintering the prefired compacted green body of predetermined shape at a maximum sintering temperature in an atmosphere containing nitrogen and an amount of hydrogen greater than or equal to about 2.5 volume percent and less than 75 volume percent for a period of time sufficient to produce a translucent polycrystalline alumina body.