Development of toroidal soft X-ray imaging system and application for investigating three-dimensional plasma on J-TEXT

A toroidal soft X-ray imaging (T-SXRI) system has been developed to investigate the three-dimensional (3D) plasma physics on J-TEXT. This T-SXRI system consists of three sets of SXR arrays. Two sets are newly developed and located on the vacuum chamber wall at toroidal position ϕ of 126.4° and 272.6°, respectively, while one set is established previously at ϕ = 65.5°. Each set of SXR arrays consists of 3 arrays viewing the plasma poloidally, and hence can be used separately to obtain the SXR imaging via the tomographic method. The sawtooth precursor oscillations are measured by T-SXRI. The corresponding images of SXR perturbations are successfully reconstructed at three toroidal positions, hence forms a 3D measurement of the sawtooth precursor. The observed 3D structure is consistent with the helical structure of the m/n = 1/1 mode. The experimental observation confirms that the T-SXRI system is capable of observing the 3D structure of the plasma.