On the outstanding problem of energy confinement in a controlled nuclear fusion system

The single most important scientific question in fusion research is confinement in a fusion plasma. A recently-developed theoretical model [1] is reviewed for the confinement time of ion kinetic energy in a material where fusion reactions occur. In the theoretical model where ion stopping was considered as a key mechanism for ion kinetic energy loss, an estimate was obtained for the confinement time of ion kinetic energy in a D-T plasma - and found to be orders of magnitude lower than required in the Lawson criterion. As ions transfer their kinetic energies to electrons via ion stopping, electron cyclotron radiation is identified as a key mechanism for electron kinetic energy loss in a magnetically confined plasma. These theoretical results are compared with measurements from TFTR, JET and Wendelstein 7-X.

1. C. Chen, J.R. Becker, and J.J. Farrell, "Confinement time of ion kinetic energy in a controlled nuclear fusion system," Proc. of 47th European Physical Socieity Conf. on Plasma Physics, P1.4006 (2021).