Placement of a Fast Ion Loss Detector Array in Wendelstein 7-X

Good confinement of α particles (He4-ions) is an essential requirement for a Stellarator fusion reactor. In contrast to Tokamak reactors with largely axisymmetric configuration, such confinement is not easy to achieve in Stellarators. To alleviate this issue, Wendelstein 7-X (W7-X) was optimized in this regard. As the experimental confirmation of the success of this optimization is pending, a novel in-wall tile fast ion loss detector is currently being developed to aid in this assessment [1]. the detector has a compact form factor, giving large flexibility in its mounting position. Furthermore, it allows installation of an array of detectors, which is beneficial as hot spots of fast ion losses change their position and magnitude depending on the configuration, as can be seen in figure 1. No estimate of global losses can therefore be made from a single measurement position, and a detector array is needed.