Highly Charged Ion Research at the Livermore Electron Beam Ion Traps

Abstract

Spectroscopy performed with the three Livermore electron beam ion traps is reviewed, which is continuing and complementing the innumerable contributions to atomic physics provided over the years by heavy-ion accelerators. Numerous spectrometers were developed that cover the spectral bands from the visible to the hard x ray region. These enabled exhaustive line surveys useful for x-ray astrophysics and for systematic studies along iso-electronic sequences, such as the 4s-4p, 3s-3p, and 2s-2p transitions in ions of the Cu-I, Na-I, and Li-I sequences useful for studying QED and correlation effects as well as for precise determinations of atomic-nuclear interactions. They also enabled measurements of radiative transition probabilities of very long-lived (milli-and microseconds) and very short-live (femtosecond) levels. Because line excitation processes can be controlled by choice of the electron beam energy, the observed line intensities are used to infer cross sections for electron-impact excitation, dielectronic recombination, resonance excitation, and innershell ionization. These capabilities have recently been expanded to simulate x-ray emission from comets by charge exchange. Specific contributions to basic atomic physics, nuclear physics, and high-temperature diagnostics are illustrated.

Ion energy distribution in an electron beam ion trap inferred from simulations of the trapped ion cloud

“…It is conventional to consider the radius of the beam or cloud to be that radius that contains 80% of the particles, r 80,e or r 80,i . Then the area overlap is given by (r 80,e /r 80,i ) 2 . For the synthetic ion cloud, we find that the overlap factor is on average 0.08 ± 0.05 (see Table II).…”

“…Electron beam ion traps (EBITs) are versatile sources for benchmarking fundamental atomic physics parameters as well as spectral fitting packages used to help interpret data measured from a variety of complex plasmas [1,2]. These traps have a cylindrical geometry with an electron beam running along the axis of the trap.…”