Speaker
Description
A thermal ion driven bursting instability with rapid frequency chirping, assessed to be an Alfvénic ion temperature gradient mode [1], has been observed in plasmas having reactor-relevant temperature in the DIII-D tokamak [2] (see the Fig. 1). The modes are excited over a wide spatial range from macroscopic device size to micro-turbulence size and the perturbation energy propagates across multiple spatial scales. The radial mode structure is able to expand from local to global in ∼ 0.1 ms, and it causes magnetic reconnection in the plasma edge, which can lead to a minor disruption event. The ηi (=∂ln$T_i$/∂ln$n_i$) exceeds the theory-predicted threshold for the destabilization of Alfvénic continuum due to compressibility of core ions. The most unstable modes belong to the strongly coupled kinetic ballooning mode and β-induced Alfvénic eigenmodes branch [3]. The key features of the observation are successfully reproduced by linear analysis solving the electromagnetic gyrokinetic equations (CGYRO code) [4]. Since the mode is typically observed in high ion temperature >10 keV and high-β plasma regime, the manifestation of the mode in future reactors should be studied with development of mitigation strategies, if needed.
https://i.ibb.co/9tH68Wt/001.jpg
*Supported by the US DOE under DE-FC02-04ER54698
[1] F. Zonca, L. Chen and R.A. Santoro, Plasma Phys. Controlled Fusion 38 2011 (1996).
[2] X.D. Du, R.J Hong, W.W. Heidbrink, X. Jian et al., Phys. Rev. Lett. 127, 025001 (2021).
[3] I. Chavdarovski and F. Zonca, Phys. Plasmas 21, 052506 (2014).
[4] J. Candy, E. Belli and R. Bravenec, J. Comput. Phys. 324, 73 (2016).
| Speaker's Affiliation | General Atomics |
|---|---|
| Member State or IGO | United States of America |
