The Electron Beam Ion Trap (EBIT) at NIST is a small laboratory device that can produce ions with extremely high charge states (e.g., Q=70+). The study of such ions is relevant to the understanding of hot astrophysical plasmas (such as those produced by supernovas or matter falling into a black hole), fusion energy devices, light sources for extreme ultraviolet microlithography, x-ray lasers, and proposed biomedical devices. In addition, we can use the EBIT to explore fundamental physics issues related to changes in atomic structure from relativity, electron correlation, and quantum electrodynamics. Visible, extreme ultraviolet, and x-ray spectrometers; and a quantum microcalorimeter are used to analyze the light emitted when the ions are excited by an electron beam of variable energy. Because the ions are confined in an electromagnetic bottle, their spectra can be studied under very well-controlled conditions and wavelengths can be precisely determined without having to correct for large Doppler shifts and other systematic errors. In addition, cross sections for dielectronic recombination, radiative recombination, ionization, and excitation can be measured. Excited state lifetimes can be determined by rapidly switching off the electron beam and measuring the temporal decay of the ion fluorescence. We also use spectroscopic signals to study the physics of trapping highly charged non-neutral plasmas. A system for extracting and analyzing the ions is available to assist in the work. In the future, we plan to use lasers to push the accuracy of measurements in highly charged ions to an unprecedented level. (See the associated research opportunity under Joseph Tan.) For additional information, see http://www.nist.gov/pml/div684/grp01/ebit.cfm. We also develop accurate collisional-radiative (CR) models which are used for identification and analysis of the EBIT data. The atomic data needed for CR modeling are calculated with the state-of-the-art atomic structure and collisions codes, some of which are being actively developed at NIST. Our CR models are also used for spectroscopic analysis of hot plasmas in fusion devices (including charge-exchange recombination and motional Stark effect), solar plasma, and laser-produced plasmas.

 

key words

Atomic spectroscopy; Atomic structure; Electron beams; Ions and ionization processes; Nuclear fusion; Space plasmas; X-ray lasers; Quantum electrodynamics; Ion traps; Highly charged ions; Ion beams; collisional-radiative modeling;

Citizenship:  Open to U.S. citizens

Level:  Open to Postdoctoral applicants