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Abstract Electron beam ion traps (EBITs) are compact devices optimized for producing ions in high charge states for spectroscopic studies or as extracted beams. Key characteristics, such as current density and electron-ion overlap, govern ionization and excitation rates. Using visible and X-ray imaging of emissions from highly charged ions, the spatial distributions of the electron beam and ion cloud in the Smithsonian Astrophysical Observatory (SAO) EBIT were measured, enabling the determination of the effective electron density. The nominal electron beam full width at half maximum (FWHM) was determined to be 92.0 ± 9.7 μm, while the ion cloud FWHM was 410.5 ± 16.5 μm, indicating an effective electron density roughly an order of magnitude lower than determined geometrically. The effects of magnetic fields on the electron beam size were also investigated, demonstrating sensitivity to the focusing magnet and bucking coil currents. These findings emphasize the need for simultaneous measurement of the effective electron density to improve the accuracy of density-sensitive studies in EBIT systems. 

Abstract In this report we describe the design and operation of the electron beam ion trap (EBIT) at the Smithsonian Astrophysical Observatory (SAO). We also provide an overview of recent upgrades that have led to improved system stability and greater user control, increasing the scope of possible experiments. Observations of X-ray emission from background elements were made after the system upgrades. The evolution of the spectrum, produced at beam energies ranging from 1285 eV to 3095 eV, allowed us to identify emission from multiple charge states and from key processes, such as dielectronic recombination, in Ba and Si ions. Emission from these background elements was easily removed by periodically dumping the trap every 2 s or less. 

AbstractMetastable levels of highly charged ions that can only decay via highly forbidden transitions can have a significant effect on the properties of high temperature plasmas. For example, the highly forbidden 3d$$^{10}$$ $_{}^{10}$$$_{J=0}$$ $_{J=0}^{}$- 3d$$^9$$ $_{}^9$4 s$$(\frac{5}{2},\frac{1}{2})_{J=3}$$ ${(\frac{5}{2},\frac{1}{2})}_{J=3}$magnetic octupole (M3) transition in nickel-like ions can result in a large metastable population of its upper level which can then be ionized by electrons of energies below the ground state ionization potential. We present a method to study metastable electronic states in highly charged ions that decay by x-ray emission in electron beam ion traps (EBIT). The time evolution of the emission intensity can be used to study the parameters of ionization balance dynamics and the lifetime of metastable states. The temporal and energy resolution of a new transition-edge sensor microcalorimeter array enables these studies at the National Institute of Standards and Technology EBIT. Graphical abstractNOMAD calculated time evolution of the ratio of the Ni-like and Co-like lines in Nd at varying electron densities compared with measured ratios