Analytic Modelling of Magneto-Rayleigh Taylor Instability Growth for Dynamic Screw Pinches

Pulsed-power-driven, Z-pinch implosions are used to study HEDP, radiation physics, and fusion energy. However, their performance is limited by Magneto-Rayleigh–Taylor instabilities (MRTI), which disrupt plasma confinement. Besides the more common method of applying a static Bz field, an effective alternative for mitigating MRTI is to drive the implosion with a helical B field that has a pitch angle that changes throughout the implosion. This can be achieved by using a dynamic screw pinch (DSP) configuration instead of a standard Z pinch (SZP). While the SZP employs a straight return-current structure, generating only a Bθ field, the DSP uses a helical return-current path, generating both a Bz and Bθ field. Experimental results have shown DSP structure is effective in suppressing MRTI growth [1]. In this work, we present an analytical model for MRTI growth for DSP. We use an analytical expression for the linear growth rate of MRTI that accounts for both Bz and Bθ fields characteristic of DSP configuration [2,3]. We further develop a numerical model to calculate the cumulative growth of the instabilities in the imploding liner in response to a prescribed current drive. This framework enables us to evaluate the instability’s evolution throughout the implosion.



[1] P. C. Campbell et al., PoP 28, 082707 (2021)

[2] M. R. Weis et al., PoP 22, 032706 (2015)

[3] D. A. Yager-Elorriaga et al., PoP 25, 056307 (2018)