Theoretical study on the laser-driven ion-beam trace probe in toroidal devices with large poloidal magnetic field

Recently, a new diagnostic method, Laser-driven Ion-beam Trace Probe (LITP), has been proposed to reconstruct 2D profiles of the poloidal magnetic field (B_p) and radial electric field (E_r) in the tokamak devices. A linear assumption and test particle model were used in those reconstructions. In some toroidal devices such as the spherical tokamak and the Reversal Field Pinch (RFP), B_p is not small enough to meet the linear assumption. In those cases, the error of reconstruction increases quickly when B_p is larger than 10% of the toroidal magnetic field (B_t), and the previous test particle model may cause large error in the tomography process. Here a nonlinear reconstruction method is proposed for those cases. Preliminary numerical results show that LITP could be applied not only in tokamak devices, but also in other toroidal devices, such as the spherical tokamak, RFP, etc.