Development of a high intensity EBIT for basic and applied science/011

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The electron-beam ion trap (EBIT) is a device for producing and studying cold, very highly charged ions of any element, up to a fully ionized U{sup 92+}. These highly charged ions occur in hot plasmas and therefore play important roles in nuclear weapons, controlled fusion, and astrophysical phenomena. The remarkable interaction of these ions with surfaces may lead to technological applications. The highly charged ions can either be studied inside the EBIT itself with measurements of their x-ray emission spectra, or the ions can be extracted from the EBIT in order to study their interaction with solid material. Both types of measurements are being pursued vigorously with the two existing low-intensity EBITs at LLNL and with similar EBITs that have been built at six other laboratories around the world since the EBIT was first developed at LLNL 10 years ago. However, all existing EBITs have approximately the same intensity as the original LLNL EBIT; that is, they all produce about the same number of very-highly-charged ions (roughly 2 x 10{sup 6} per second) and the same number of x-ray photons (roughly 10{sup 7} per second). The goal of the High-Intensity-EBIT project is to increase the x-ray emission per centimeter of length along the electron beam by a factor of 100 and to increase the ion output by a factor of 1000. This dramatic increase in intensity will enable the next generation of basic and applied experimental research in the structure of highly charged ions. For example, the precision of EBIT x-ray measurements of atomic energy levels- which is now limited by count rate-can be improved by an order of magnitude, and new applications in surface science, nanotechnology, and microscopy will be possible with the expected intense ion beams. When the high ion output is combined with the demonstrated low emittance of EBIT ions, we will have a high-brightness source of highly charged ions that can be focused to submicrometer spots. One example of a measurement that will benefit from increased x-ray intensity is our study of the binding energy of high-Z heliumlike ions. The small ``two-electron`` contribution to this binding energy is a fundamental aspect of atomic structure. It arises from the small forces that the two electrons exert on each other in the presence of the much larger force from the atomic nucleus. Our existing EBIT measurements are sensitive to the so-called ``second order`` contribution to the two-electron binding energy, but with the High-Intensity EBIT we can probe an even more subtle effect: the screening by one electron of the quantum electrodynamic (QED) energy contribution from the other electron.