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The new pellet injection system for refuelling the ASDEX Upgrade tokamak with cubic H(2) or D(2) pellets has alternative side lengths of 1.5, 1.75 and 2.0 mm and optional Ne doping. The system delivers series of about one hundred pellets at a maximum repetition rate of more than 40 Hz. The pellets are accelerated by means of a centrifuge with an optimised straight acceleration arm. This configuration minimises the compulsive force acting on the pellet during the acceleration process. Since this also minimises stresses inside the pellet, high velocities (a maximum of 1211 m/s being achieved) are possible without destroying the hydrogen cubes. A special pellet feed-in technique based on a static stop cylinder interrupting the acceleration path successfully reduced the horizontal scattering angle to values of less than +/- 4 . Thus, a high efficiency, with more than 90 % of the pellets arriving within the acceptance angle, was achieved without using a guide tube. The whole system was found to work very reliably and reproducibly during the entire test operation period, covering about 100,000 pellet shots. The new centrifuge, now integrated into the ASDEX Upgrade setup, has proved to be a reliable unit even for long operation periods, offering the possibility of quasicontinuous particle refuelling throughout a plasma discharge in ASDEX Upgrade.

Additional information

Authors: ANDELFINGER C ET AL., Max-Planck-Institut für Plasmaphysik, Garching bei München (DE)
Bibliographic Reference: Article: Review of Scientific Instruments, Vol. 64 (1993) No. 4, pp. 983-989
Record Number: 199311143 / Last updated on: 1994-11-29
Original language: en
Available languages: en
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