April 4-6

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approvednew_mesoscopic_modes_associated_with_impurity_populations.pdf2022-03-04 10:06:57Bruno Coppi


Author: Bruno Coppi
Requested Type: Consider for Invited
Submitted: 2022-03-03 08:51:27

Co-authors: B. Basu

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Cambridge, MA   02139
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Abstract Text:
Plasma collective modes associated with impurity populations in magnetically confined plasmas had been identified in Ref. [1] followed by relevant analyses. These modes had frequencies well below the cyclotron frequencies of the ion populations and could be classified as microinstabilities. The newly identified modes have frequencies close to the impurity cyclotron frequency, are electrostatic in the limit $k_⊥^2 d_i^2≫1$ and involve significant magnetic field fluctuations [2], for $k_⊥^2 d_i^2≤1$. Here $k_⊥ $ is the transverse (to the magnetic field) mode number and $d_i=c⁄ω_pi$ refers to the main ion population. A growth rate is found as a combined effect of the maximum impurity density gradient and of a particle (impurity) diffusion coefficient. The possible interaction with the lower frequency modes introduced in Ref. [1] is re-examined in this context. Relevant experiments [3] concerning transport of impurity and main ion populations are considered in relation to the presented theory.
Sponsored in part by C.N.R. of Italy and the Kavli Foundation (through MIT).

1. B. Coppi, H. Furth, M. Rosenbluth and R. Sagdeev, Phys. Rev. Lett. 17, 377 (1966).
2. B. Coppi, S. Cowley, R. Kulsrud, P. Detragiache and F. Pegoraro, Phys. Fluids 29, 4060 (1986).
3. C. Mazzotta, et al. Paper IAEA-CN-899 MFE, Fusion Energy Conference (I.A.E.A., Vienna, 2021).