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The M-intrashell spectra from Co-like Yb43+ through Na-like Yb59+ ions produced in an electron beam ion trap (EBIT) at the National Institute of Standards and Technology have been studied in the extreme ultraviolet (EUV) range. A few N-intrashell transitions for Co-like Yb43+ and Fe-like Yb44+ are also reported. The EUV radiation was observed with a flat-field grazing incidence spectrometer in the wavelength region of about 7.5 nm to 26.2 nm. The electron beam energies were varied between 3.6 keV and 18 keV to produce the ionization stages of interest. The line identifications were based on the large-scale simulations of the EBIT plasma emission using the non-Maxwellian collisional-radiative code NOMAD. A total of 76 previously unobserved spectral lines corresponding to electric-dipole and magnetic-dipole transitions in the above mentioned ions were identified and discussed. In particular, our accurate wavelength of 24.3855 ± 0.0005 nm for a magnetic-dipole (M1) transition in the ground configuration of Co-like ion presents a solid benchmark for comparisons with the most advanced theories of atomic structure. [ABSTRACT FROM AUTHOR]

Accurate extreme ultraviolet spectra of open N-shell neodymium (Nd) ions were recorded at the electron beam ion trap facility of the National Institute of Standards and Technology. The measurements were performed for nominal electron beam energies in the range of 0.90 keV to 2.31 keV. The measured spectra were then compared with the spectra simulated by a collisional-radiative model utilizing atomic data produced with a fully relativistic atomic structure code. Consequently, 59 lines from Br-like to Ni-like Nd ions were unambiguously identified, most of which were newly assigned in this study. The wavelengths of 9 known lines from Ni-, Cu- and Zn-like Nd ions were in excellent agreement with previous measurements. [ABSTRACT FROM AUTHOR]

Non-thermal electron distributions, such as beams of electrons, are found in many laboratory and astrophysical plasma sources and can produce anisotropic and polarized emission. Theories used to model the emission require sublevel specific analysis, which can be difficult to verify experimentally. Using two polarization-sensitive Johann-type crystal spectrometers at the National Institute of Standards and Technology (NIST) electron beam ion trap facility, we measured the linear polarization of well-known dielectronic recombination satellite transitions from Li-like Ar ions and two blended features from Be-like ions. The spectrometers observed the plasma at 90° relative to the electron beam propagation direction, and the crystal dispersion planes were oriented perpendicular relative to each other to allow for differing polarization sensitivities. Measurements were taken near the resonance energies of each line and compared with theoretical predictions based on relativistic magnetic sublevel atomic kinetics using the density-matrix theory. Most of the predictions are in excellent agreement with measured values. [ABSTRACT FROM AUTHOR]

High-resolution x-ray spectra were recorded at the National Institute of Standards and Technology electron beam ion trap (EBIT) using two Johann-type crystal spectrometers, with their dispersion planes oriented parallel and perpendicular to the beam direction. The linear polarizations of the 1s2 − 1s2l transitions in He-like argon ions were determined from the measured spectra at electron beam energies of 3.87 and 7.91 keV. The theoretical analysis was performed using detailed collisional-radiative modeling of the non-Maxwellian EBIT plasma with the NOMAD code modified to account for magnetic sublevel atomic kinetics. Effects influencing the polarizations of the observed 1s2 − 1s2l lines were investigated, including radiative cascades, the 1s21S0 − 1s2s1S0 two-photon transition, and the charge exchange recombination of H-like argon ions. With these included, the measured polarizations of the resonance (1s21S0 − 1s2p1P1), intercombination (1s21S0 − 1s2p3P1), and forbidden lines (1s21S0 − 1s2s3S1, 1s21S0 − 1s2p3P2) were found to be in good agreement with the calculations. [ABSTRACT FROM AUTHOR]

We report on the design, commissioning, and initial measurements of a Transition-Edge Sensor (TES) x-ray spectrometer for the Electron Beam Ion Trap (EBIT) at the National Institute of Standards and Technology (NIST). Over the past few decades, the NIST EBIT has produced numerous studies of highly charged ions in diverse fields such as atomic physics, plasma spectroscopy, and laboratory astrophysics. The newly commissioned NIST EBIT TES Spectrometer (NETS) improves the measurement capabilities of the EBIT through a combination of high x-ray collection efficiency and resolving power. NETS utilizes 192 individual TES x-ray microcalorimeters (166/192 yield) to improve upon the collection area by a factor of ∼30 over the 4-pixel neutron transmutation doped germanium-based microcalorimeter spectrometer previously used at the NIST EBIT. The NETS microcalorimeters are optimized for the x-ray energies from roughly 500 eV to 8000 eV and achieve an energy resolution of 3.7 eV–5.0 eV over this range, a more modest (<2×) improvement over the previous microcalorimeters. Beyond this energy range, NETS can operate with various trade-offs, the most significant of which are reduced efficiency at lower energies and being limited to a subset of the pixels at higher energies. As an initial demonstration of the capabilities of NETS, we measured transitions in He-like and H-like O, Ne, and Ar as well as Ni-like W. We detail the energy calibration and data analysis techniques used to transform detector counts into x-ray spectra, a process that will be the basis for analyzing future data. [ABSTRACT FROM AUTHOR]

High-resolution x-ray spectra were recorded at the National Institute of Standards and Technology electron beam ion trap (EBIT) using two Johann-type crystal spectrometers, with their dispersion planes oriented parallel and perpendicular to the beam direction. The linear polarizations of the 1s2 − 1s2l transitions in He-like argon ions were determined from the measured spectra at electron beam energies of 3.87 and 7.91 keV. The theoretical analysis was performed using detailed collisional-radiative modeling of the non-Maxwellian EBIT plasma with the NOMAD code modified to account for magnetic sublevel atomic kinetics. Effects influencing the polarizations of the observed 1s2 − 1s2l lines were investigated, including radiative cascades, the 1s21S0 − 1s2s1S0 two-photon transition, and the charge exchange recombination of H-like argon ions. With these included, the measured polarizations of the resonance (1s21S0 − 1s2p1P1), intercombination (1s21S0 − 1s2p3P1), and forbidden lines (1s21S0 − 1s2s3S1, 1s21S0 − 1s2p3P2) were found to be in good agreement with the calculations. [ABSTRACT FROM AUTHOR]

Highly charged tungsten transitions can be used as a diagnostic tool for investigating performance of the fusion device. Systematic spectroscopic investigations of the radiative decay channels of the tungsten charge states allow for extending the fundamental understanding of highly charged ions and can serve as a diagnostic tool to improve applied plasma research. Electron beam ion traps (EBIT) offer the ability to generate emission from highly charged tungsten ions because of their charge state and excitation selectivity due to their quasi-monoenergetic electron beam. In this work, we report the current experimental capabilities of the EBIT at the National Institute of Standards and Technology (NIST). High-resolution measurements of EUV and x-ray transitions from tungsten charge states are shown, demonstrating our ability to produce and identify the spectral features of highly charged tungsten plasma. While the experimental results were limited by the lack of an absolute calibration of the spectrometer, we present approximate transition energies of two strong transitions from the Ti-like W 52+ and Sc-like W 53+ charge states. Our estimates agree quite well with the results of FAC simulations, where these strongest transitions were identified to originate from 3d-4f transitions. This decay channel has been shown to be the strongest transition for surrounding charge states. [ABSTRACT FROM AUTHOR]

We report a new test of quantum electrodynamics (QED) for the w (ls2p1Pl --· ls2IS0) x-ray resonance line transition energy in heliumlike titanium. This measurement is one of few sensitive to two-electron QED contributions. Systematic errors such as Doppler shifts are minimized in our experiment by trapping and stripping Ti atoms in an electron beam ion trap and by applying absolute wavelength standards to calibrate the dispersion function of a curved-crystal spectrometer. We also report a more general systematic discrepancy between QED theory and experiment for the w transition energy in heliumlike ions for Z > 20. When all of the data available in the literature for Z = 16-92 are taken into account, the divergence is seen to grow as approximately Z3 with a statistical significance on the coefficient that rises to the level of 5 standard deviations. Our result for titanium alone, 4749.85(7) eV for the w line, deviates from the most recent ab initio prediction by 3 times our experimental uncertainty and by more than 10 times the currently estimated uncertainty in the theoretical prediction. [ABSTRACT FROM AUTHOR]

Abstract: We report here our methods and results of measurements of very low-signal X-ray spectra produced by highly charged ions in an electron beam ion trap (EBIT). A megapixel Si charge-coupled device (CCD) camera was used in a direct-detection, single-photon-counting mode to image spectra with a cylindrically bent Ge(220) crystal spectrometer. The resulting wavelength-dispersed spectra were then processed using several intrinsic features of CCD images and image-analysis techniques. We demonstrate the ability to clearly detect very faint spectral features that are on the order of the noise due to cosmic-ray background signatures in our images. These techniques remove extraneous signal due to muon tracks and other sources, and are coupled with the spectrometer wavelength dispersion and atomic-structure calculations of hydrogen-like Ti to identify the energy of a faint line that was not in evidence before applying the methods outlined here. [Copyright &y& Elsevier]