Full-orbit and drift calculations of fusion product losses due to explosive fishbones on JET

Full-orbit and drift calculations of fusion product losses due to explosive fishbones on JET

Full-orbit and drift calculations of fusion product losses due to explosive fishbones on JET 150 150 Mathew
UKAEA-CCFE-PR(18)28

Full-orbit and drift calculations of fusion product losses due to explosive fishbones on JET

Fishbones are ubiquitous in high-performance JET plasmas and are typically considered to be unimportant for scenario design. However, during recent high-performance hybrid experiments, sporadic and explosive fishbones have been observed which correlate with a reduction in performance and main chamber hotspots. Clear evidence has been obtained of fusion products being non-resonantly ejected from the plasma by the fishbones. In this work, we present detailed calculations of the motion of fusion products in the presence of fishbones using all available information on the nature of the fishbones observed. Using careful reconstruction of the equilibrium, measurements of the perturbation, and drift and full orbit following calculations, we will show that the fusion product losses can be well modelled by a linear MHD internal kink mode structure. In the drift and full orbit calculations ignoring the proximity of the wall to the plasma, the energy content of those losses is insufficient to explain the observed hotspots, however a combination of magnetic moment scattering and wall proximity may be sufficient.

Collection:
Journals
Journal:
Nuclear Fusion
Publisher:
IOP
Published date:
14/11/2018