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P: Fachverband Plasmaphysik
P 17: Magnetic Confinement V/HEPP VI
P 17.5: Vortrag
Mittwoch, 28. Februar 2024, 17:55–18:10, ELP 6: HS 3
Development of an ECRH plasma start-up scenario for X3 heating at 1.8 T at Wendelstein 7-X — •Niklas Simon Polei, Torsten Stange, Frank Noke, Frank Hollmann, Heinrich Peter Laqua, and W7-X Team — Max-Planck-Institut für Plasmaphysik, 17491 Greifswald
One of the main goals of the Wendelstein 7-X stellarator is to show good confinement of fast particles in high beta scenarios. Beta is the ratio of kinetic pressure and magnetic pressure β = 2 n T/B2/2µ 0. The available power of the electron cyclotron resonance heating (ECRH) system is not sufficient to reach the necessary beta of 4-5% at 2.5 T, but higher beta values are expected at lower magnetic field. To still use the existing gyrotrons at 140 GHz, X3 heating has to be used at a field of 1.8 T, but a plasma start-up is not possible because Te>0.5keV is needed for sufficient absorption. Therefore, the combination of ion cyclotron resonance heating and neutral beam injection has been considered as the start-up scenario so far. The usual ECRH X2 start-up is also possible, if one gyrotron is operated near its other operating point at 104 GHz.
However, operation at 101 GHz is necessary and was succesfully demonstrated for 100 ms with a power of 300 kW. Additionally, a multi-pass scenario with six passes through the plasma axis was developed to maximise the power density during the first 10−20 ms of plasma initiation. For this purpose, two new tiles were designed and the beam positions of the different passes were verified in the plasma vessel in preperation for the next operation phase 2.2.
Keywords: ECRH; Wendelstein 7-X; Gyrotrons; Plasma start-up