Speaker
Description
The rigorous evaluation of magnetically trapped particle dynamics in 3D perturbed magnetic fields in toroidal magnetized plasmas remains a fundamental theoretical challenge. Standard bounce-averaging methods are often too rough or produce artificial singularities near the turning points due to the distortion of magnetic surfaces. This mathematical difficulty becomes a crucial physical issue for energetic particles with large trapped-orbit widths and rapid precession frequencies.
To systematically resolve this issue, we propose an Isomagnetic Guiding-Center (IGC) transformation based on noncanonical Lie transformation theory [1,2]. This methodology systematically rectifies a distorted magnetic field into an isomagnetic surface prior to the standard bounce-center transformation [3,4]. Instead of artificially truncating the perturbation, we rigorously encode the perturbed field and displacement into the generator and the gauge function, respectively. By pulling back the dynamics from the isomagnetic space, our formalism systematically isolates the secular radial drift from the bounce-angle-dependent oscillating part without breaking the underlying Hamiltonian structure. Furthermore, the identification of the general bounce-drift resonance and the description of the resultant superbanana orbit are also presented.
References
[1] Robert G. Littlejohn, J. Math. Phys. 23, 742 (1982)
[2] Allen J. Brizard and Taik Soo Hahm, Rev. Mod. Phys. 79, 421 (2007)
[3] Robert G. Littlejohn, Phys. Scr. 1982, 119 (1982)
[4] John R. Cary and Allen J. Brizard, Rev. Mod. Phys. 81, 693 (2009)