|Title||NBI-driven Alfvenic modes at ASDEX Upgrade|
|Publication Type||Journal Article|
|Year of Publication||2012|
|Authors||P. Lauber, I.G.J. Classen, D. Curran, V. Igochine, B. Geiger, S. da Graca, M. García-Muñoz, M. Maraschek, P. McCarthy|
|Type of Article||Article; Proceedings Paper|
|Keywords||EXPLANATION, MHD SPECTROSCOPY, N=0 CHIRPING MODE, STABILITY, TOKAMAKS|
A large variety of electromagnetic modes excited by NBI-generated energetic ions are observed in the early phase of many discharges at ASDEX Upgrade. In addition to the well-known reversed shear Alfven eigenmodes (RSAE) and the toroidal Alfven eigenmodes (TAE), a set of modes around 70 kHz is observed as recently described in . The modes were identified to be beta-induced Alfven eigenmodes (BAE) connected with the appearance of the q = 2 and the q = 1.5 surface during the current ramp-up phase. In the view of ITER, these BAEs may occur in scenarios with q approximate to 2 (scenario 4) and therefore add significantly to the transport of energetic ions due to RSAEs and TAEs. Experimentally, the combination of ECE, soft-x-ray and magnetic measurements allows for a very reliable mode position and mode structure determination. The measurements are compared with linear gyrokinetic calculations employing the LIGKA code that uses a fully kinetic model to describe fast-particle-driven modes in general tokamak geometry.
|Alternate Title||Nucl. Fusion|
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