New extruder-based deuterium feed system for centrifuge pellet injection

The pellet injection systems for the next-generation fusion devices (such as the International Thermonuclear Experimental Reactor) and future fusion reactors will have to provide deuterium-tritium fueling for much loner pulse lengths (up to approximate to 1000 s) than present applications (typically limited to less than several seconds). Thus, a prototype pellet feed system for centrifuge pellet injection has been developed and used in long-pulse (> 100 s) tests at the Oak Ridge National Laboratory (ORNL). The new apparatus has two key components: (1) a cryogenic deuterium extruder and (2) an electromagnetic pellet punch mechanism. For maximum testing flexibility, the prototype is equipped with several other active components that allow remote adjustments, including precise positioning of the punch and the capability to index through eight different pellet lengths. The new feed system was designed to mate with an existing centrifuge accelerator facility at ORNL, and experiments in the facility were carried out to document the performance and reliability of the new feed system. With 2.3-mm-diam deuterium pellets and a catenary-shaped accelerator (approximate to 1.2 m diam), the prototype feed system was found to be capable of placing up to approximate to 90% of the punched pellets in the proper time/space window for pickup and acceleration by the high-speed rotating (approximate to 50 Hz) arbor. For these operating parameters, the pellet nominal speed was approximate to 430 m/s, and maximum pellet feed rates of 10 pellets/s and greater were tested. 18 this article the equipment is briefly described, and the experimental test results are summarized. Also, issues affecting overall pellet delivery efficiency are discussed. (C) 1997 American Institute of Physics.