Fast-ion velocity-space tomography using slowing-down regularization in EAST plasmas with co- and counter-current neutral beam injection
B. Madsen, J. Huang, M. Salewski, H. Järleblad, Per Christian Hansen, L. Stagner, Jingzhi Su, J. F. Chang, Jia Fu, Junwen Wang, Lizhen Liang, Guoqiang Zhong, Yingying Li, Baokuo LYU, Haiqing Liu, Qing Zang, Zhengping Luo, M. Nocente, D. Moseev, Tieshuan Fan, Y. M. Zhang, Danke Yang, Jiaqi Sun, Longyong Liao
Abstract
Abstract We demonstrate 2D reconstructions of the fast-ion velocity distribution from two-view fast-ion D-alpha (FIDA) measurements at the EAST tokamak. By expressing the distribution in a basis relying on the fast-ion slowing-down process in fusion plasmas, the smoothness and velocity-space resolution of reconstructions are improved. We reconstruct distributions of fast ions born from simultaneous co- and counter-current neutral beam injection and detect the expected distinct change in fast-ion birth pitch when comparing discharges utilizing different neutral beam injectors. For purely co-current injection, we find a good agreement between TRANSP-predicted and reconstructed fast-ion densities, pressures and current densities for energies above 20 keV. We furthermore illustrate the improvement of the reconstructed high-energy range (> 40 keV) of the distribution by combining FIDA with neutron emission spectroscopy measurements with the compact single-plate EJ301 scintillator.