The Wendelstein 7-X phase contrast imaging diagnostic

Abstract

A phase contrast imaging (PCI) diagnostic has been developed for the Wendelstein 7-X (W7-X) stellarator. The PCI diagnostic provides line-integrated measurement of turbulent electron density fluctuations, which is essential for understanding and achieving high performance scenarios that can lead to improved confinement at fusion-relevant temperatures and densities. The PCI system is also sensitive to coherent fluctuations, which arise from Alfvén eigenmodes or other MHD activity. This paper provides an overview of the hardware and the optical system and presents an example of PCI measurement from the W7-X OP1.2b experimental campaign.