Fast-ion orbit analysis in Thailand Tokamak-1

Thailand Tokamak-1 (TT-1) will be a small research tokamak being operated by the Thailand Institute of Nuclear Technology (TINT) in Nakhonnayok province, Thailand. The device partly uses the infrastructure of the former HT-6M alongside new hardware. Auxiliary heating sources, such as ion cyclotron range of frequency (ICRH) and/ or neutral beam injection (NBI), maybe also included in subsequent operations. This study aims to investigate the characteristics and behavior of fast ions produced by NBI heating in various operation scenarios. This work employs the collisionless Lorentz-orbit (LORBIT) code for simulating the motion of ions in the TT-1. When a hydrogen ion (H+) with an energy of 20 keV travels in the plasma with the plasma current of 100 kA, the toroidal magnetic field of 1.0 T, the average Larmor radius is found to approximately be 0.48 cm for a passing transit particle and 2.17 cm for a trapped particle. The Larmor radius reduces as the plasma current is increased or a stronger magnetic field is used. Furthermore, when the ion has pitch angles in the range of 85 degrees-100 degrees, the ion orbit clearly demonstrates a banana shape with a width and height of 7.0 and 18.8 cm, respectively. The size of the banana orbit shows an inverse correlation with the plasma current. In the last part of this work, we investigate the motion of ions that had initial positions along the paths of a co-current and counter-current NBI. It is shown that the number of lost ions can be reduced if the initial radial positions of the ions are in the range of 0.64-0.68 m.