Stabilization of Liner Implosions via a Dynamic Screw Pinch

Area of Science:

• Plasma physics
• High-energy density physics
• Magnetohydrodynamics

Background:

• Magnetically driven implosions face challenges from magnetohydrodynamic instabilities like the magneto-Rayleigh-Taylor instability (MRTI).
• The dynamic screw pinch (DSP) configuration, utilizing a helical magnetic field, has been theoretically proposed to mitigate MRTI growth in solid-metal liner implosions.

Purpose of the Study:

• To experimentally validate the effectiveness of the dynamic screw pinch (DSP) configuration in suppressing magneto-Rayleigh-Taylor instability (MRTI) during solid-metal liner implosions.
• To compare the MRTI growth in DSP-driven implosions with that of a standard z-pinch (SZP) configuration.

Main Methods:

• Experiments were conducted using the COBRA pulsed-power driver (1-MA, 100-200 ns).
• Solid-aluminum liners (3.2 mm initial radius, 650 nm thick) were imploded using three DSP configurations with varying axial magnetic fields (2 T, 14 T, 20 T) and one standard z-pinch (SZP) configuration (zero axial field).
• Instability growth was monitored through imaging during implosion.

Main Results:

• Helical MRTI modes were observed in DSP-driven implosions, while nonhelical modes dominated the SZP case.
• MRTI amplitudes were significantly reduced in the 14 T and 20 T DSP cases compared to the SZP.
• At half the initial radius, MRTI amplitudes were 1.1±0.3 mm (SZP), 0.7±0.2 mm (14 T DSP), and 0.3±0.1 mm (20 T DSP).

Conclusions:

• The dynamic screw pinch (DSP) configuration effectively reduces magneto-Rayleigh-Taylor instability (MRTI) growth in solid-metal liner implosions.
• Experimental results show good agreement with theoretical predictions for MRTI stabilization using DSP.
• DSP offers a promising method for enhancing the stability of magnetically driven implosions for applications like inertial confinement fusion.