Speaker
Jacob Eriksson
Description
See the full Abstract at http://ocs.ciemat.es/EPS2018ABS/pdf/I1.104.pdf
Measuring fast ions in fusion plasmas
with neutron diagnostics
J. Eriksson1, F. Binda1, M. Cecconello1, S. Conroy1, G. Ericsson1, C. Hellesen1, V.G.
Kiptily2, M. Mantsinen3, M. Nocente4, A. Sahlberg1, M. Salewski5, S. Sharapov2 and JET
Contributors †
1
Dept. of physics and astronomy, Uppsala University, Sweden
2
CCFE, Culham Science Centre, Abingdon, Oxfordshire, UK
3
BCS and ICREA, Barcelona, Spain
4
Dipartimento di Fisica and Istituto di Fisica del Plasma, Milano, Italy
5
Department of Physics, Technical University of Denmark, Kgs. Lyngby, Denmark
A high-performance fusion plasma inevitably contains a population of supra-thermal ions,
with energies in the range from ∼100 keV to a few MeV, that are produced either in the fusion
reactions or by the plasma heating systems. Such “fast ions” can drive plasma instabilities,
and their confinement in the plasma is important to maintain the high temperature required
for fusion. Fusion plasmas consisting of deuterium (D) or a deuterium-tritium mixture (DT)
are sources of intense neutron emission due to the D+D and D+T fusion reactions (at the JET
tokamak neutron rates of 5.5⋅1016 s-1 and 5.7⋅1018 s-1 have been achieved in D and DT
plasmas, respectively), and fast ions often leave characteristic signatures in the neutron
emission. In this presentation, we will show how neutron measurements can be used to study
fast ions and give examples of results obtained at JET and other present day tokamaks.
It is often possible to determine the fast D energy distribution from neutron spectroscopy
measurements. With this technique it is possible to study energy dependent interactions
between the fast ions and MHD activity, as well as the fast ion dynamics in plasmas heated
with neutral beam injection (NBI) and ion cyclotron radio-frequency heating (ICRH).
An even more detailed picture of the fast ion distribution can be obtained by combining
several different diagnostics. We show how the fast ion distribution can be resolved in both
energy and pitch angle by combining neutron and gamma-ray measurements obtained along
several different sightlines using velocity-space tomography.
Finally, we give an outlook about neutron-based fast ion measurements at the next
generation fusion experiment, ITER.
†
See the author list of “X. Litaudon et al 2017 Nucl. Fusion 57 102001”
