Mapping of the HIDRA Magnetic Flux Surfaces Through Experimental Measurements and Computational Codes

Determining the shape of the plasma inside the Hybrid Illinois Device for Research and Applications (HIDRA) is essential to conduct desired Plasma Material Interactions (PMI) experiments. This will be especially critical in the testing of two liquid lithium plasma facing components, the LiMIT and FLiLi limiters. For this, a zinc oxide painted fluorescent rod was used to sweep across a poloidal cross-section and detect the electrons emitted from an electron gun moving radially inside the vacuum vessel. With long exposure shots, the electron traces were captured and used to build up the experimental magnetic flux surfaces (FSs) for the toroidal position of θ = 216. These have been measured for several iota values of 1/3, 1/4 and 1/5. Measurements to investigate the effect of adding a vertical coil current on the radial position of the FS center as well as the central and outer iota values were also conducted. Then, using computer codes such as FIELDLINES and TORMESH, experimental and computational FSs were matched, giving information about the actual shape of the plasma, the value of the error field inside HIDRA, and the offset of the plasma center with respect to the magnetic axis.