RESUMO
Mo wire X pinches typically emit several x-ray bursts from a bright spot near the crossing of the X -pinch wires. Streak camera images of L -shell line emission from Mo wire X pinches have been analyzed using a non-local thermodynamic equilibrium (NLTE) collisional-radiative atomic kinetics model, providing temperature and density profiles with approximately 50 ps time resolution over the approximately 350 ps x-ray bursts. In conjunction with nonspectroscopic measurements, the analysis is used to propose a picture of the dynamic evolution of the X -pinch plasma. The L -shell spectra from the first x-ray burst indicate an electron density near 10(22) cm(-3) and an electron temperature near 1 keV; subsequent x-ray bursts have L -shell spectra that indicate electron temperatures slightly above 1 keV and electron densities near 10(20) and 10(21) cm(-3). The size of the L -shell line-emitting region is estimated to be near 10 microm for the first x-ray burst and much larger for the later bursts. It is proposed that inner-shell excitation of low ionization stages of Mo in a microm -scale plasma region contributes to the observed radiation from the first micropinch, which typically emits a short burst of >3 keV radiation and has L -shell spectra characterized by broad spectral lines overlaying an intense continuum.
RESUMO
Using an X-pinch configuration, we have determined that micropinches produced by exploding-wire z pinches can have densities approaching solid density and temperatures of 0.5-1.8 keV, depending upon the wire material used. These plasma parameters, determined from x-ray spectra recorded using an x-ray streak camera, vary drastically on time scales ranging from <10 to 100 ps. Computer simulations require radiation loss to reproduce the observed plasma implosion, suggesting that a radiative-collapse hypothesis for micropinch plasma formation may be correct.
