HIGH REPETITION INBOARD LAUNCH OF HYDROGEN PELLETS

The centrifuge hydrogen pellet injection system at ASDEX Upgrade was e xtended far inboard launching. Successful and efficient inboard pellet refueling was realized up to pellet velocities of about 400 m/s. In o rder to achieve maximum available pellet particle rates of the system still at the low centrifuge revolution needed in this velocity range, the injector has been modified. Thus, operational conditions have been developed yielding the potential to inject pellets at rather low spee d but high repetition rate. Since pellets injected from the inboard ar e obviously not hampered by the low velocity but show better performan ce than fast pellets injected from the outside, this scheme seems to a llow for an efficient and flexible particle refueling of hot plasmas. The system is now capable of launching pellet series at rates up to 60 Hz at a speed of 240 m/s. With the biggest available pellet size, thi s enables a pellet particle flux of 2.6x10(22)/s. (C) 1998 American In stitute of Physics. [S0034-6748(98)02507-6].