Achieving Strong Magnetization with the Convergence of Subcritical Density Plasma Flows*

Magnetized warm dense matter samples are unexplored experimentally due to the large magnetic field strengths required to magnetize the samples [1]. While most high-energy-density (HED) flux compression schemes have reached large fields of kilo-Tesla strengths, they require a converging high-density plasma to achieve flux compression [2-4]. The convergence is detrimental to both the formation of the sample, which requires a clear line of sight with the heating beam, and its diagnosis, which also requires a clear line of sight to probe the sample using X-rays. However, convergence can also be achieved using a low-density high-temperature plasma, where the plasma thermal pressure is larger than the magnetic pressure. By reducing the converging plasma density and increasing its temperature, large magnetic fields can be obtained while keeping a clear line of sight to generate HED sample and diagnose it using X-rays. This halfraum setup [5] is promising to magnetize HED plasma experimentally. Our 3-D simulations in PERSEUS [6]  indicate that achieving such strong fields with the convergence of subcritical plasma flows is possible in a cylindrical geometry. Possible 3-D instabilities in the setup are investigated by comparing these results to the results in 2-D [5]. The results presented form a baseline for pioneering experiments to study magnetized HED samples.

[1] J. Meyer-ter Vehn and R. Ramis, Physics of Plasmas 26, 113301 (2019).

[2] O. V. Gotchev, et al., Phys. Rev. Lett. 103, 215004 (2009).

[3] J. P. Knauer, et al., Physics of Plasmas 17, 056318 (2010), https://doi.org/10.1063/1.3416557.

[4] D. Barnak, et al., Physics of Plasmas 24, 056310 (2017).

[5] I. N. Erez, et al., (2024), arXiv:2311.00879 [physics.plasm-ph].

[6] C. E. Seyler and M. R. Martin, Physics of Plasmas 18, 012703 (2011), https://doi.org/10.1063/1.3543799.