NOVELTY - Apparatus (300) for high pressure material processing comprises a cylindrical capsule region; an annular heating member (305) enclosing the cylindrical capsule region; and at least two assembled rings disposed around a perimeter of the annular heating member, where the assembled rings comprises at least a high strength enclosure ring (301) overlying an annular ceramic member (303) having a thickness, where the annular member is made of a material having a compressive strength of at least about 0.5 GPa and a thermal conductivity of less than about 4 watts per meter-Kelvin.    USE - As apparatus for high pressure material processing; and for growing crystals to be used in the manufacture of light emitting diodes (claimed); and for processing supercritical fluids. The crystals include crystals of gallium nitride, aluminum nitride, indium nitride, indium gallium nitride, aluminum gallium nitride, aluminum indium gallium nitride, and others used for manufacture of bulk or patterned substrates that are used in a variety of applications including optoelectronic devices, lasers, light emitting diodes, solar cells, photoelectrochemical water splitting and hydrogen generation, photodetectors, integrated circuits, transistors and other devices.    ADVANTAGE - The apparatus is capable of effectively accessing pressures and temperatures of 0.2-2 GPa and 400-1200 degrees C respectively. The apparatus provides a high pressure apparatus for crystal growth; is scalable up to very large volumes and is cost effective. The apparatus can operate with components that are relatively simple and cost effective to manufacture, such as ceramic and steel tubes. The apparatus also takes advantage of the cracks provided in the ceramic member, which insulates the heater. The apparatus can be manufactured using conventional materials and/or methods of the prior art. The apparatus enables cost-effective crystal growth and materials processing under extreme pressure and temperature conditions in batch volumes larger than 0.3 l, larger than 1 l, larger than 3 l, larger than 10 l, larger than 30 l, larger than 100 l, and larger than 300 l.    DETAILED DESCRIPTION - Apparatus (300) for high pressure material processing comprises a cylindrical capsule region; an annular heating member (305) enclosing the cylindrical capsule region; and at least two assembled rings disposed around a perimeter of the annular heating member, where the assembled rings comprises at least a high strength enclosure ring (301) overlying an annular ceramic member (303) having a thickness, where the annular member is made of a material having a compressive strength of at least about 0.5 GPa and a thermal conductivity of less than about 4 watts per meter-Kelvin. The apparatus further comprises a capsule (307) disposed within the cylindrical capsule region; and a cylindrical sleeve member disposed overlying the at least one annular ceramic member. The apparatus further comprises a first end flange (317) and a second end flange. When the apparatus contains at least one continuous annular metal or cermet member having a thickness disposed continuously around perimeter of the member, the apparatus comprises a high strength enclosure material disposed overlying the annular metal or cermet member to form a high strength enclosure. An INDEPENDENT CLAIM is included for apparatus for growing crystals to be used in the manufacture of light emitting diodes comprising: a cylindrical capsule; a gallium nitride seed crystal and a supercritical fluid disposed within the cylindrical capsule; an annular heater surrounding at least a portion of the cylindrical capsule; at least two ceramic rings disposed around the annular heater; and a metal enclosure surrounding the at least two ceramic rings, where the annular heater is used to heat the supercritical fluid disposed within the cylindrical capsule to form a gallium nitride boule which after being removed from the cylindrical capsule is divided into wafers and light emitting diodes are formed on the wafers.    DESCRIPTION OF DRAWING(S) - The figure shows simplified side view diagram of a high pressure apparatus.    Apparatus (300)    High strength enclosure ring (301)    Ceramic ring (303)    Heater (305)    Capsule (307)    Pressure transmission medium (309)    End plugs (311)    End plug jackets (313)    Fasteners (315)    End flanges (317)