X-ray spectroscopy of high-z ions

X-ray spectroscopy is a tool of choice for studying the properties of high-Z ions and provides valuable data to test atomic models, excitation cross section and atomic structure calculations. Measurements are presented of highly charged heliumlike and neonlike ions from tokamak observations and the electron beam ion trap at Livermore which illustrate unresolved questions of atomic physics and state-of-the-art approaches to address the issues