Setup and first operation of the Wendelstein 7-X ICRH matching system

For single generator operation, the matching system for the W7-X ICRH antenna consists of a line stretcher and a shunt stub, both with a mechanically variable length. The system uses a feed-forward scheme, whereby the complex voltage reflection coefficient, as well as the forward and reflected RF power, is measured during an RF pulse via two directional couplers located on the generator side of the matching unit. This complex reflection coefficient is combined with a numerical model of the matching unit and the known line stretcher and shunt stub positions to determine the impedance on the antenna side. The required matching solution is then found using a Bang-Bang algorithm, and the line stretcher and shunt stub are positioned for the next pulse. The matching system was successfully operated during the W7-X experimental campaign OP 2.1. This paper describes the calibration and testing of the necessary RF sensors, modeling and testing of the matching unit with artificial loads, and its operation during OP 2.1.