Analysis of RSAE Radial Phase Variation in DIII-D Discharges

The radial phase variation of the eigenfunction of reversed shear Alfven eigenmodes (RSAE) depends upon the plasma shape. The eigenfunctions of RSAEs often exhibit radial variations in phase,¹ an effect that can be caused by fast-ion gradients,¹ symmetry breaking,² and radial energy flows.³ The phase change at the outer peak of the eigenfunction is measured by an electron cyclotron emission radiometer diagnostic and entered into a database.  The measured phase change correlates more strongly with “gapin” than with any other parameter, with a clear difference between diverted and limited discharges. (“Gapin” is the spacing between the inner wall and the last closed flux surface.) Representative DIII-D cases are analyzed by NOVA-K, MEGA, and FAR3d and compared with the data.

 

¹B.J. Tobias et al., Phys. Rev. Lett. 106 (2011) 075003.

²Z.X. Lu et al., Pl. Phys. Cont. Fusion 61 (2019) 044005.

³G.J. Kramer et al., Nucl. Fusion 59 (2019) 094001.