Precision X-ray spectroscopy at the NIST electron-beam ion trap: Resolution of major systematic error

Some of the most critical tests of the QED Lamb shifts are currently being pursued in the X-ray regime by investigating the core levels of medium Z at oms such as vanadium. Toe current approach to the measurement of the Lamb s hift in such a system is outlined. We present major progress in understandi ng and reducing the systematic errors within our system. The error budget h as been reduced to a level where critical tests of QED can be performed. Re cent observations of Lyman a in hydrogenic vanadium at the NIST Electron-Be am Ion Trap are presented.