REDISTRIBUTION OF FAST IONS IN JET AND ITER BY SAWTOOTH OSCILLATIONS

 

Yu. V. Yakovenko^1,2, V. V. Lutsenko¹, V. Kiptily³, L. Giacomelli⁴, T. Craciunescu⁵,
V. Ya. Goloborod’ko¹, B. S. Lepiavko¹, A. I. Tishchenko^1,2, H. Weisen⁶, S. Sharapov³,
Ya. I. Kolesnichenko¹, JET Collaborators⁷

 

¹ Institute for nuclear research of NAS of Ukraine, Kyiv, Ukraine

² National University of Kyiv Mohyla Academy, Kyiv, Ukraine

³ Culham Centre for Fusion Energy, Abingdon, United Kingdom

⁴ Istituto di Fisica del Plasma “P. Caldirola”, CNR, Milano, Italy

⁵ EURATOM-MedC Association, National Institute for Laser, Plasma and Radiation Physics, Bucharest, Romania

⁶ Swiss Plasma Center, École Polytechnique Fédérale de Lausanne, Lausanne, Switzerland

⁷ See the author list of “X. Litaudon et al 2017 Nucl. Fusion 57 102001″

 

Results of simulations of the sawtooth-induced redistribution of fast ions with the code OFSEF [1] are presented. The dependence of the redistribution on the particle parameters (energy and pitch angle) is studied. The behavior of passing and deeply trapped particles agrees with results of earlier works [1, 2]. The redistribution of the trapped and marginally passing particles is found to exhibit barrier-like behaviour at the separatrix between the trapped and passing particles: the particles with high energies cannot pass the radial coordinate corresponding to the separatrix. The OFSEF simulation results provide a basis for a new rapid code. The algorithm and structure of this code are discussed. The code is verified by comparing its results with OFSEF results.

Predictive simulations of the sawtooth effect on fusion alpha particles in the ITER reactor are carried out; they show that when the shape of the q-profile is non-parabolic (which is expected, for example, in the hybrid mode), the post-crash radial profile of the alpha particle distribution function can change significantly.

Experimental observations of the sawtooth effect on the neutron emission in several recent discharges of the JET tokamak are presented and discussed. In most JET discharges, neutron mainly result from fusion reactions of NBI (neutral beam injection) produced fast ions, which are mostly passing. In discharges with 3^rd-harmonic ICRH (ion cyclotron resonance heating), a significant part of the neutron flux results from ICRH-accelerated ions, which are trapped MeV ions [3]. Simulations of the sawtooth-induced redistribution in different discharges (which is now in progress) can be used for the verification of the theory [2].

This work has been carried out within the framework of the EUROfusion Consortium and has received funding from the Euratom research and training programme 2014—2018 under grant agreement No 633053 and from the National Academy of Sciences of Ukraine under the Project “Phenomena associated with energetic ions in tokamaks and stellarators” and the Project No PL15/19. The views and opinions expressed herein do not necessarily reflect those of the European Commission.

 

1.    Ya. I. Kolesnichenko, V. V. Lutsenko, Yu. V. Yakovenko and G. Kamelander. Phys. Plasmas 4, 2544 (1997).

2.    Ya. I. Kolesnichenko and Yu. V. Yakovenko. Nucl. Fusion 36, 159 (1996).

3.    J. Eriksson et al. Nucl. Fusion 55, 123026 (2015).