Novel high-energy sources for QED tests

A major problem in most X-ray QED measurements is the presence of satellite contamination and Doppler shifts and broadening from fast beam sources. Recently, new sources known as Electron Beam Ion Traps (pictured) have been shown to avoid much of these problems, and still allow desired charge states to be produced and measured.

The EBIT or Electron Beam Ion Trap, has been successfully run at three institutions around the world. This has paved the way for more careful and critical tests of QED, together with a wide range of other experiments still under construction. A beauty of this source is that the charge state is selectable by the potential applied, due to the balance of ionisation and recombination processes. Yet this device can fit inside a normal sized laboratory - or even an office - with only a slightly-more-than-normal-sized budget.

Our involvement in this research is in several directions: we have close connections with both the Oxford and N.I.S.T. / N.R.L. EBIT sources and are involved in several specific investigations at these facilities.

This topic is closely linked to the

precision tests of QED.