How exactly do individual particles actually move in fusion plasmas? - Part 2

This simulation takes a look inside the ASDEX Upgrade tokamak and shows the path of two "fast" hydrogen ions (in this case deuterium nuclei). They are shot into the vacuum vessel at the beginning of the animation by neutral particle injection to heat up the plasma. We see the motion of the gyrocenter of the particles. The helical gyration motion is averaged out here. The two particles illustrate the difference between "trapped" and "passing" ions.
The first part of the video shows a "passing" ion, the second a "trapped" one. What is the difference? Towards the center of the large radius (hole of the donut) the magnetic field strength in the tokamak increases. The gyration motion of the particles causes a maximum magnetic field strength (determined by the injection conditions) which the particle cannot exceed. If this maximum magnetic field strength is higher than the strengths occurring in the plasma, we have a passing particle, which approximately follows the magnetic field lines. Otherwise, it is called a trapped or "banana particle" - due to the shape of the motion in the projection to the cross-section of the torus. The existence of the trapped particle significantly changes the behavior of the whole plasma.
The particle was simulated by IPP PhD student David Kulla using the BEAMS3D code being developed at IPP by Samuel Lazerson. The animation was created in Blender.