ECRH-assisted breakdown in the TCA tokamak
ECRH-assisted breakdown studies are currently being performed on the TCA tokamak to determine the effectiveness of ECRH preionisation in reducing the required toroidal breakdown loop voltage and increasing reproducibility and controllability of the start-up phase. These results will affect operation of the TCV device, in which the continuous vacuum vessel impedes purely inductive start-up. The ECRH system includes a 39 GHz gyrotron which outputs TE(02) with an efficiency of more than 35%. The mode structure is measured by a wave-number spectrometer before the power is mode filtered and finally launched in HE(11) after crossing the waveguide omega(ce) resonance. The power is reflected by a rotatable, focussing mirror located inside the vacuum vessel and results in X-mode HFS launch. Results show a reduction in the loop voltage required for breakdown (approx. 0.3 V/m achieved) and an increased start-up reliability. Plasma parameter dependence on ECRH power, prefill pressure, and resonance position are also being investigated. Details of the gyrotron system and ECRH-assisted start-up results are presented.
Bibliographic Reference: Paper presented: 32nd Annual Meeting of the American Physical Society, Division of Plasma Physics, Cincinnati (US) Nov. 12-16, 1990
Availability: Available from (1) as Paper EN 35636 ORA
Record Number: 199110797 / Last updated on: 1994-12-02
Original language: en
Available languages: en