Interferometric measurements of the plasma density at the Z-pinch periphery in the angara-5-1 facility

Abstract

Knowledge of spatial mass distribution is important for understanding the physics of implosion of megaampere-current wire arrays. The paper presents results from studying the electron density distribution at the periphery of a tungsten wire array near the instant of maximum compression by using laser interferometry at λ=0.69 µm. It is found that, at the instant of maximum compression (∼100 ns after the beginning of the discharge), the estimated maximum local electron density inside the wire array reaches ∼10¹⁸ cm⁻³ at a distance of 0.3–3 mm from the initial wire positions. Assuming the average tungsten ion charge to be 10, the local linear mass density in this region turns out to be 3 µg/cm, which amounts to about 10% of the total linear mass density of the liner. A fraction of the generator current flows through this plasma. The duration of the soft X-ray pulse is 5–8 ns, which indicates the achievement of a fairly high compression ratio.