Polarization spectroscopy of x-ray transitions from beam-excited highly charged ions

Polarization spectroscopy of x-ray lines represents a diagnostic tool to ascertain the presence of electron beams in high-temperature plasmas. Making use of the Livermore electron beam ion trap, which optimizes the linear x-ray line polarization by exciting highly charged ions with a monoenergetic electron beam, we have begun to develop polarization diagnostics and test theoretical models. Our measurement relies on the sensitivity of crystal spectrometers to the linear polarization of x-ray Lines which depends on the value of the Bragg angle. We employed two spectrometers with differing analyzing crystals and simultaneously recorded the K-shell emission from heliumlike Fe24+ and Lithiumlike Fe23+ ions at two different Bragg angles. A clear difference in the relative intensities of the dominant transitions is observed, which is attributed to the amount of linear polarization of the individual lines. (C) 1997 American Institute of Physics.