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The design, construction and testbed results for a novel compact gas gun injector for solid diagnostic pellets of different sizes and materials are reported. The injector was optimised for the diagnostic requirements of the ASDEX Upgrade tokamak, yielding the possibility of a widely varying deposition profile of ablated material inside the plasma. The use of spherical carbon pellets and different propellant gases (He,N(2),H(2)) resulted in an accessible velocity range from about 150 m/s to more than 600 m/s and pellet masses from 2 x 1.0 E18 to 1.0 E20 atoms. The injector provided both high efficiency and high reliability during the whole testbed operation period and also during the first injection experiments performed on ASDEX Upgrade. Pellet acceleration was mostly caused by gas drag. Additional acceleration increasing with the pellet diameter (contrary to the gas drag model) may be explained by the influence of the pellet on the gas dynamics in the barrel.

Additional information

Authors: LANG P T ET AL., Max-Planck-Institut für Plasmaphysik, Garching bei München (DE);EGOROV S M ET AL., State Technical University of St. Petersburg (RU)
Bibliographic Reference: Article: Review of Scientific Instruments, Vol. 65 (1994) No. 7, pp. 2316-2321
Record Number: 199411441 / Last updated on: 1994-12-06
Original language: en
Available languages: en