Charge-State Distribution and Doppler Effect in an Expanding Photoionized Plasma

Abstract

The charge state distributions of Fe, Na, and F are determined in a photoionized laboratory plasma using high resolution x-ray spectroscopy. Independent measurements of the density and radiation flux indicate unprecedented values for the ionization parameter xi=20-25 erg cm s(-1) under near steady-state conditions. Line opacities are well fitted by a curve-of-growth analysis which includes the effects of velocity gradients in a one-dimensional expanding plasma. First comparisons of the measured charge state distributions with x-ray photoionization models show reasonable agreement.

Experimental astrophysics with high power lasers andZpinches

“…GALAXY is a collisional-radiative code that calculates the steady-state ionization balance within the plasma, given density, temperature, and incident radiation field as input ͑Rose, 1998; Foord et al, 2004Foord et al, , 2006Rose et al, 2004͒. Collisional and radiative excitation and ionization as well as autoionization and all reverse processes are included.…”

“…NIMP is a non-LTE, average-atom model ͑Djaoui and Rose, 1992;Rose et al, 2004͒. It follows the time evolution of principal quantum shell occupancies, averaged over the distribution of ionic states.…”

“…The measured electron density is n e ϳ 2 ϫ 10 19 cm −3 . Also, calculations show that electrons and ions equilibrate rapidly, so the ion temperature T i can be taken to equal T e ͑Foord et al, 2004. The code CLOUDY, when allowed to calculate the electron temperature and run with a model consistent with the measured saturation of the Fe resonance lines, finds T e = 150 eV.…”

“…Shown for comparison is a peak-normalized T r = 165 eV black-body spectrum. Adapted from Foord et al, 2004. ͑b͒ X-ray spectrum in a scaled experiment done on the Z-pinch facility.…”

Photoionizational Plasmas. I. Theory

“…Recently, high-Z photoionized plasmas were produced in several laboratory experiments (Foord et al 2004;Fujioka et al 2009;Wang et al 2008Wang et al , 2009). Their analysis sheds new light on the spectra from such plasmas (Fujioka et al 2009;Drake 2009) and stimulated the demand for a systematic study of photoionized plasmas not only as a tool for astrophysics but also as a research topic per se.…”