High power helium beams for TEXTOR and He-pumping capability of the NBI vacuum and cryosystem
The neutral beam injectors of TEXTOR usually operated in H(2) or D(2) are capable of producing 2.3 MW 4He-beams at 50 kV, 45 A and several seconds duration with a repetition rate of 7 min and one day operation without regeneration of the cryopumps. Measured beam characterising data are 1.1 deg vertical divergence, a neutralisation efficiency of 77% and a beamline transmission of 55%, derived from waterflow calorimetry of the beamline structures. The installed 8 Chevron cryopumps work without modifications at a temperature of 4.2 K with approximately 36% of the pumping speed of H(2). Careful preconditioning of the cryosurfaces with argon is essential. Optimum Ar/He ratios are between 15:1 and 40:1. The He beamline pressure stays below 8 x 1.0 E-5 mbar, giving a low reionisation of 1-2%. TEXTOR results show stable plasma conditions with unimportant argon contamination during 4He-injection into a D(2)-plasma.
Bibliographic Reference: Article: Fusion Technology 1990, Vol. 2 (1991) pp. 1191-1195
Record Number: 199111190 / Last updated on: 1994-12-02
Original language: en
Available languages: en