Simulated correction to poloidal charge-exchange recombination spectroscopy measurement in a tokamak

Taking into account the effects of atomic processes and the observation angle, a simple code modelling the correction to the poloidal charge-exchange recombination spectroscopy (CXRS) measurement in a tokamak is developed, which is an effective tool to correct the deviation in CXRS measurements. The simulated results show that the measured poloidal velocity shift is overestimated in the ion diamagnetic drift direction and the apparent ion temperature is underestimated because of the effects of the energy-dependent emission rate, finite lifetime of excited ions and the observation direction. This deviation will be more obvious with an increase in temperature, magnetic field, or observation angle. In the core region, the pseudo-shift coming from the observation angle effect is much more significant than that from others. The contributions from gradients of density and temperature are negligible compared to that from emission rate, lifetime and observation angle effects. Using the corrected velocity, a radial electric field (Er) well is formed near the internal transport barrier (ITB) location for a typical plasma on the Japan Atomic Energy Research Institute Tokamak-60 Upgrade (JT-60U). It seems that the poloidal rotation enhances Er shear, which is speculated to be related to the ITB formation.