D C Pace et al 2011 Plasma Phys. Control. Fusion 53 062001 doi:10.1088/0741-3335/53/6/062001
D C Pace1, R K Fisher2, M García-Muñoz3, W W Heidbrink1 and M A Van Zeeland2
Show affiliationsCoherent losses of neutral beam ions are observed at frequencies corresponding to toroidal and reversed-shear Alfvén eigenmodes (RSAEs) in DIII-D. Reversed-shear profiles are created by injecting beam power during the plasma current ramp. Beam ion losses stemming from Alfvén eigenmode activity contribute to flattening of the energetic ion density profile in such discharges. This is the first observation of convective beam ion losses due to RSAEs. The energies and pitch angles of lost ions are measured and found to exist within a well-defined region of phase space. Loss flux signals decrease in time as current penetrates and Alfvén eigenmode activity becomes more core localized. Preliminary Monte Carlo simulations of energetic ion interactions with measured mode structures show the dominant loss mechanism is a transition from a counter-passing orbit to a trapped orbit that is lost to the wall.
52.35.Bj Magnetohydrodynamic waves (e.g., Alfven waves)
52.40.Hf Plasma-material interactions; boundary layer effects
Issue 6 (June 2011)
Received 16 December 2010, in final form 29 March 2011
Published 21 April 2011
D C Pace et al 2011 Plasma Phys. Control. Fusion 53 062001
S J Zweben et al 2007 Plasma Phys. Control. Fusion 49 S1
B Labit et al 2007 Plasma Phys. Control. Fusion 49 B281
A H Khater and S M Moawad 2003 Plasma Phys. Control. Fusion 45 265
B C Stratton et al 2002 Plasma Phys. Control. Fusion 44 1127
I H Hutchinson 2002 Plasma Phys. Control. Fusion 44 1953
G Fuchs and V Pickalov 1998 Plasma Phys. Control. Fusion 40 91
R A Brooker 1955 Br. J. Appl. Phys. 6 307
P D Jarman and K J Taylor 1964 Br. J. Appl. Phys. 15 321
N Ryde and B Andersson 1955 Proc. Phys. Soc. B 68 1117