The next experimental campaign at the next generation stellarator Wendelstein 7-X in Greifswald, Germany is commencing testing for the first time island divertor concept in combination with highly optimized plasma core performance. One key task of such a divertor is to exhaust neutral particles and impurities and control plasma density as well as impurity density. UW Madison PhD student Thierry Kremeyer has developed a unique neutral gas measurement device which has been implemented into W7-X.
This new, miniaturized in-situ Penning probe head enables investigating the neutral gas composition directly in the neutral compression region (baffling) of the island divertor at W7-X. This system is now implemented at three positions in one half-module (i.e. at one toroidal location). A state of the art light detection system from the oak Ridge national laboratory ORNL is used for fast time resolution and simultaneous measurement of H? and three He-I lines. This unique set of spectroscopy is aiming on delivering first time spectroscopic information about the plasma state inside of the gauge, while measuring at the same tome the total neutral pressure reliably. Further refinements of the system are pending depending on the outcome of the first deployment now. A comprehensive experimental proposal has been accepted and is being implemented into the run plan to investigate the helium exhaust features of the island divertor with various magnetic configurations. This project is funded by the Department of Energy under grant DE-SC0014210.
— News: 09-27-2017