Polarization is important for analyzing line emission in the infrared, visi
ble, and ultraviolet [see A. N. Zaidel and E. Ya. Shreider, Vacuum Spectros
copy and Its Application [in Russian], Nauka, Moscow, 1976] and also for x
rays. Experimental results are presented for x rays from heliumlike argon i
n a plasma focus discharge, and ways in which polarized x rays might be cre
ated by directional electrons or electric/magnetic fields are discussed. (C
) 1999 American Institute of Physics. [S0021-3640(99)00712-4].