# Kink instability

One of the earliest photos of the kink instability in action - the 3 by 25 cm pyrex tube at Aldermaston.

A kink instability (also kink oscillation or kink mode), is a current-driven plasma instability characterized by transverse displacements of a plasma column's cross-section from its center of mass without any change in the characteristics of the plasma. It typically develops in a thin plasma column carrying a strong axial current which exceeds the Kruskal–Shafranov limit[1][2][3] and is sometimes known as the Kruskal–Shafranov (kink) instability.[4][5]

The kink instability was first widely explored in fusion power machines with Z-pinch configurations in the 1950s.[6] It is one of the common magnetohydrodynamic instability modes which can develop in a pinch plasma and is sometimes referred to as the ${\displaystyle m=1}$ mode.[6] (The other is the ${\displaystyle m=0}$ mode known as the sausage instability.)

If a "kink" begins to develop in a column the magnetic forces on the inside of the kink become larger than those on the outside, which leads to growth of the perturbation.[6][7] As it develops at fixed areas in the plasma, kinks belong to the class of "absolute plasma instabilities", as opposed to convective processes.

## References

1. ^ Ryutov, D. D.; Furno, I.; Intrator, T. P.; Abbate, S.; Madziwa-Nussinov, T. (2006). "Phenomenological theory of the kink instability in a slender plasma column". Physics of Plasmas. 13 (3): 032105. doi:10.1063/1.2180667. ISSN 1070-664X.
2. ^ DeHaas, Timothy; Gekelman, Walter; Van Compernolle, Bart (2015). "Experimental study of a linear/non-linear flux rope". Physics of Plasmas. 22 (8): 082118. doi:10.1063/1.4928888. ISSN 1070-664X.
3. ^ Oz, E.; Myers, C. E.; Yamada, M.; Ji, H.; Kulsrud, R. M.; Xie, J. (2011). "Experimental verification of the Kruskal-Shafranov stability limit in line-tied partial-toroidal plasmas". Physics of Plasmas. 18 (10): 102107. doi:10.1063/1.3647567. ISSN 1070-664X.
4. ^ Cap, Ferdinand F. (2013-09-11). Handbook on Plasma Instabilities. Academic Press. ISBN 9781483271057.
5. ^ Hasegawa, A. (2012-12-06). Plasma Instabilities and Nonlinear Effects. Springer Science & Business Media. ISBN 9783642659805.
6. ^ a b c Zohuri, Bahman (2017-02-23). Magnetic Confinement Fusion Driven Thermonuclear Energy. Springer. pp. 46–48. ISBN 9783319511771.
7. ^ Plasma Dictionary Archived 2006-09-29 at the Wayback Machine