Open AccessOn the Evolution From Micrometer-Scale Inhomogeneity to Global Overheated Structure During the Intense Joule Heating of a z-Pinch Rod
Author(s) -
T. J. Awe,
E. P. Yu,
K. C. Yates,
W. G. Yelton,
B. S. Bauer,
T. M. Hutchinson,
S. Fuelling,
B. B. Mckenzie
Publication year - 2017
Publication title -
ieee transactions on plasma science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.46
H-Index - 106
eISSN - 1939-9375
pISSN - 0093-3813
DOI - 10.1109/tps.2017.2655450
Subject(s) - engineered materials, dielectrics and plasmas , fields, waves and electromagnetics
Ultrafast optical microscopy of metal z-pinch rods pulsed with megaampere current is contributing new data and critical insight into what provides the fundamental seed for the magneto-Rayleigh-Taylor (MRT) instability. A two-frame near infrared/visible intensified-charge-coupled device gated imager with 2-ns temporal resolution and 3-μm spatial resolution captured emissions from the nonuniformly Joule heated surfaces of ultrasmooth aluminum (Al) rods. Nonuniform surface emissions are consistently first observed from discrete, 10-μm scale, subelectronvolt spots. Aluminum 6061 alloy, with micrometer-scale nonmetallic resistive inclusions, forms several times more spots than 99.999% pure Al 5N; 5-10 ns later, azimuthally stretched elliptical spots and distinct strata (40-100 μm wide by 10 μm tall) are observed on Al 6061, but not on Al 5N. Such overheat strata, which are aligned parallel to the magnetic field, are highly effective seeds for MRT instability growth. These data give credence to the hypothesis that early nonuniform Joule heating, such as the electrothermal instability, may provide the dominant seed for MRT.