Speaker
Dr
Ken McClements
(CCFE)
Description
Fast particle-driven waves in the ion cyclotron frequency range (ion cyclotron emission or ICE) have provided a valuable diagnostic of confined and escaping fast ions in many tokamaks. This is a passive, non-invasive diagnostic that would be compatible with the high radiation environment of DT plasmas in ITER, and could provide important information on fusion alpha-particles and beam ions in that device. In JET ICE from confined fusion products scaled linearly with fusion reaction rate over six orders of magnitude [1] and provided evidence that alpha-particle confinement was close to classical [2]. In TFTR ICE was observed from super-Alfvenic alpha-particles in the plasma edge [3]. The intensity of beam-driven ICE in DIII-D is more strongly correlated with drops in neutron rate during fishbone excitation than signals from more direct beam ion loss diagnostics [4]. In ASDEX Upgrade ICE is produced by both super-Alfvenic DD fusion products and sub-Alfvenic D beam ions [5]. The magnetoacoustic cyclotron instability (MCI), driven by the resonant interaction of population-inverted energetic ions with fast Alfven waves, provides a credible explanation for ICE. One-dimensional PIC and hybrid simulations have been used to explore the nonlinear stage of the MCI [6,7], thereby providing a more exact comparison with measured ICE spectra and opening the prospect of exploiting ICE more fully as a fast ion diagnostic. For realistic values of fast ion concentration, the nonlinearly-saturated ICE spectrum closely resembles the measured spectrum. The PIC/hybrid approach should soon make it possible to simulate the nonlinear physics of ICE in full toroidal geometry. Emission has been observed at a wide range of poloidal locations, and so there is flexibility in the requirements of an ICE detector. Such a detector could be implemented in ITER by installing a toroidal loop or adding a detection capability to the ICRH antennae.
This work was part-funded by the RCUK Energy Programme and by the European Union's Horizon 2020 programme.
[1] G.A. Cottrell et al., NF 33 (1993) 1365
[2] K.G. McClements et al. PRL 82 (1999) 2099
[3] S.J. Zweben et al., NF 40 (2000) 91
[4] W.W. Heidbrink et al., PP&CF 53 (2011) 085028
[5] R. D’Inca et al., Proc. 38th EPS Conf. Plasma Phys., P1.053 (2011)
[6] L. Carbajal et al., PoP 21 (2014) 012106
[7] J.W.S. Cook et al., PP&CF 55 (2013) 065003.
| Country or International Organisation | UK |
|---|---|
| Paper Number | TH/P3-28 |
Primary author
Dr
Ken McClements
(CCFE)
Co-authors
Prof.
Bill Heidbrink
(University of California)
Dr
Bob Harvey
(CompX)
Dr
James Cook
(University of Warwick)
Mr
Leopoldo Carbajal
(University of Warwick)
Prof.
Richard Dendy
(CCFE)
Dr
Rodolphe D'Inca
(Max-Planck-Institut für Plasmaphysik)
Prof.
Sandra Chapman
(University of Warwick)
Dr
Simon Pinches
(ITER Organization)
