High-speed repetitive pellet injector for plasma fueling of magnetic confinement fusion devices

The projected fueling requirements of future magnetic confinement devices for controlled thermonuclear research [e.g., the International Thermonuclear Experimental Reactor (ITER)] indicate that a flexible plasma fueling capability is required. This includes a mix of traditional gas puffing and low- and high-velocity deuterium-tritium pellets. Conventional pellet injectors (based on light gas guns or centrifugal accelerators) can reliably provide frozen hydrogen pellets (1- to 6-mm-diam sizes tested) up to /spl sim/1.3-km/s velocity at the appropriate pellet fueling rates (1 to 10 Hz or greater). For long-pulse operation in a higher velocity regime (>2 km/s), an experiment in collaboration between Oak Ridge National Laboratory (ORNL) and ENEA Frascati is under way. This activity will be carried out in the framework of a collaborative agreement between the U.S. Department of Energy and European Atomic Energy Community-ENEA Association. In this experiment, an existing ORNL hydrogen extruder (equipped with a pellet chambering mechanism/gun barrel assembly) and a Frascati two-stage light gas gun driver have been combined on a test facility at ORNL. Initial testing has been carried out with single deuterium pellets accelerated up to 2.1 km/s with the two-stage driver; in addition, some preliminary repetitive testing (to commission the diagnostics) was performed at reduced speeds, including sequences at 0.5 to 1 Hz and 10 to 30 pellets. The primary objective of this study is to demonstrate repetitive operation (up to /spl sim/1 Hz) with speeds in the 2- to 3-km/s range. In addition, the strength of extruded hydrogen ice as opposed to that produced in situ by direct condensation in pipe guns can be investigated. The equipment and initial experimental results are described.

[1]  C. Foster.  Solid deuterium centrifuge pellet injector , 1983 .

[2]  Silvio Migliori,et al.  A new two-stage pellet injector for FTU , 1989, IEEE Thirteenth Symposium on Fusion Engineering.

[3]  S. K. Combs,et al.  Operation of a repeating pneumatic hydrogen pellet injector on the Tokamak Fusion Test Reactor , 1986 .

[5]  S. L. Milora,et al.  Rview of pellet fueling , 1981 .

[6]  Wayne A Houlberg,et al.  Density profile control in a fusion reactor using pellet injection , 1994 .

[7]  M. J. Gouge,et al.  High-speed repetitive pellet injector prototype for magnetic confinement fusion devices , 1993 .

[8]  R. W. Kincaid,et al.  QUICKGUN: An algorithm for estimating the performance of two-stage light gas guns , 1990 .

[10]  M. J. Gouge,et al.  Design considerations for single-stage and two-stage pneumatic pellet injectors , 1989 .

[11]  P. W. Fisher,et al.  Tritium pellet injector for TFTR , 1992 .

[12]  E. Giovannozzi,et al.  MHD and confinement during pellet injection on FTU , 1993 .

[13]  Thomas C Jernigan,et al.  Performance of a pneumatic hydrogen‐pellet injection system on the Joint European Torus , 1989 .

[14]  S. K. Combs,et al.  Pellet injection technology , 1993 .

[15]  M. Gouge,et al.  A combined microwave cavity and photographic diagnostic for high‐speed projectiles , 1990 .

[16]  S. K. Combs,et al.  A three-barrel repeating pneumatic pellet injector for plasma fueling of the Joint European Torus , 1988 .

[17]  A. Geraud,et al.  TORE SUPRA HIGH SPEED PELLET INJECTOR , 1993 .

[18]  S. L. Milora,et al.  Review of hydrogen pellet injection technology for plasma fueling applications , 1989 .

[19]  R. Carlevaro,et al.  Experiments with the CNPM gas gun for minimizing piston wear and propellant gas flow , 1993, 15th IEEE/NPSS Symposium. Fusion Engineering.

[20]  G. Riva,et al.  Modeling of Pellet Acceleration by Two-Stage Guns , 1989 .

[21]  M. J. Gouge,et al.  Design of a tritium pellet injector for TFTR , 1991, [Proceedings] The 14th IEEE/NPSS Symposium Fusion Engineering.

[22]  S. K. Combs,et al.  Repeating pneumatic hydrogen pellet injector for plasma fueling , 1985 .