Investigation of plasma instabilities in the stagnatedZpinch

Abstract

High-resolution laser probing diagnostics at a wavelength of 266 nm allow observation of the internal structure and instabilities in dense stagnated Z pinches, typically hidden by trailing material. The internal structure of the 1-MA Z pinch includes strong kink and sausage instabilities, loops, flares, and disruptions. Mid- and small-scale density perturbations develop in the precursor and main pinch. The three-dimensional shape and dynamics of the wire-array Z pinch are predetermined by the initial configuration of the wire array. Cylindrical, linear, and star wire-array Z pinches present different sets of instabilities seeded to the pinch at the implosion stage. Prolonged implosion of trailing mass can enhance x-ray production in wire arrays. Fast plasma motion with a velocity >100 km/s was observed in the Z pinch at stagnation with two-frame shadowgraphy. Development of instabilities in wire arrays is in agreement with three-dimensional magnetohydrodynamic simulations.

Study of micro-pinches in wire-array Z pinches

“…Electron temperatures of micropinches of 0.3-3 keV were measured in different wire-array Z pinches. 4,[18][19][20] Continuum spectra of hot spots in the keV range may be a signature of a high plasma density. 16,17 Recently, axially resolved spectroscopy and K-shell power measurements were applied to stagnated Al, Cu, and Ti Z pinches on the Z machine.…”

“…The three-dimensional (3D) structure of the pinch depends on the initial configuration of the wire array. 19,20 Therefore, the dynamics and parameters of the plasma in wire-array bright spots may vary over a wide range. MHD simulation of hot spots in the wire array requires calculations with single micron accuracy, picosecond resolution, and appropriate radiation models.…”

“…[7][8][9][10][11][12] The electron temperature in bright spots (micro-pinches, hot spots, plasma points) varies from 0.3 to 3 keV in different experiments and pinch configurations. 3,4,13,14,[18][19][20][21] Micro-pinches in Z-pinch plasmas are the source of enhanced x-ray radiation. They contribute to the energy balance, x-ray production, and neutron yield in Z pinches.…”

Visualization of the magnetic field and current path in Z-pinch and X-pinch plasmas

“…The break is, presumably, produced by the collapse and explosion of the micropinch on the Z-pinch [13]. Micropinches are typical for implosions of cylindrical loads at the Zebra facility [8]. The expanded trailing plasma implodes later and produces additional kinetic energy which results in enhanced pinch radiation [9].…”

“…Ultraviolet (UV) laser diagnostics at the wavelength of 266 nm provide a flexible method to study dense Zpinch plasmas. The UV diagnostics show a strong advantage over diagnostics employed at the standard wavelength of 532 nm due to smaller absorption and less refraction at density gradients, allowing the probing laser to penetrate deeper into the dense plasma [7,8]. This also allows the Faraday rotation diagnostic to measure magnetic fields and study the current distribution in the trailing plasma of the stagnated Z pinch [9].…”