[en] We present accurate wavelength measurements of nickel L-shell X-ray lines resulting from Δn (ge) 1 transitions between 9 and 15 (angstrom). We have used the electron beam ion trap, SuperEBIT, at the Lawrence Livermore National Laboratory and a flat field grating spectrometer to record the spectra. The most significant emission lines of Ni XIX-XXVI in our spectral coverage are identified, and their relative intensities are determined. The resulting data set provides valuable input to the analyses of high-resolution X-ray spectra of stellar coronae sources, including the Sun.

[en] We report the measurement of the Kβ₂/Kβ₁ ratio of He-like krypton using the SuperEBIT electron beam ion trap at the Lawrence Livermore National Laboratory. The energy of these lines are about 15 keV, which is twice as high as the energy of such lines measured before. A comparison with theoretical predictions shows poor agreement, concerning the trend uncovered earlier where the measured result is considerably larger than predicted.

[en] Measurements of the L-shell emission of highly charged gold ions were made under controlled laboratory conditions using the SuperEBIT electron beam ion trap, allowing detailed spectral observations of lines from ironlike Au⁵³⁺ through neonlike Au⁶⁹⁺. Using atomic data from the Flexible Atomic Code, we have identified strong 3d_5/2 → 2p_3/2 emission features that can be used to diagnose the charge state distribution in high energy density plasmas, such as those found in the laser entrance hole of hot hohlraum radiation sources. We provide collisional-radiative calculations of the average ion charge < Z> as a function of temperature and density, which can be used to relate charge state distributions inferred from 3d_5/2 → 2p_3/2 emission features to plasma conditions, and investigate the effects of plasma density on calculated L-shell Au emission spectra

[en] Using the SuperEBIT electron beam ion trap, we have measured the 2s_1/2-2p_1/2 transitions in U⁸⁸⁺ and U⁸⁹⁺. The measured value of 280.645±0.015 eV for Li-like U⁸⁹⁺ improves the available precision by nearly an order of magnitude and establishes a new benchmark for testing the total QED contribution to the transition energy within a fractional accuracy of 3.6x10^-4. We infer a value for the 2s two-loop Lamb shift in U⁸⁹⁺ of -0.23 eV, from which we estimate a value of -1.27 eV for the 1s two-loop Lamb shift in U⁹¹⁺

[en] We present the absolute calibration of the continuum x-ray spectrometer (ConSpec), designed to measure the hot-spot electron temperature of inertial confinement fusion (ICF) implosions at the National Ignition Facility (NIF). The spectrometer measures emission from photon energies of 20 to 30 keV where opacity effects in ICF implosions at the NIF are negligible and provides spatial resolution to separate the hot-spot emission from other x-ray sources, such as the gold emission from the hohlraum wall. Using a combination of x-ray ray tracing and calibration data taken using a well characterized x-ray source, we measure the dispersion, spatial resolution, and absolute sensitivity of the instrument. Finally, we present an example spectrum measured at the NIF and demonstrate the ability to measure the hot-spot electron temperature with uncertainty under 10%.

[en] We have used the EBIT Calorimeter Spectrometer (ECS), a microcalorimeter instrument built by the calorimeter group at the NASA/Goddard Space Flight Center, to make a variety of measurements since its installation at Lawrence Livermore National Laboratory's EBIT facility. These include measurements of charge exchange between neutral gas and K- and L-shell ions, measurements of the X-ray transmission efficiency of optical blocking filters, high resolution measurements of transition energies for high-Z, highly charged ions, and measurements of M and L-shell emission from highly charged tungsten following on earlier measurements of L-shell gold. Our results will see application in the interpretation of the spectra from the Jovian atmosphere and of the diffuse soft X-ray background, in tests of QED, and in diagnosing inertial and magnetic confinement fusion plasmas. These measurements augment previous laboratory astrophysics, atomic physics, and calibration measurements made using earlier versions of NASA's microcalorimeter spectrometer

[en] The Livermore electron beam ion trap facility has recently been moved to a new location within LLNL, and new instrumentation was added, including a 32-pixel microcalorimeter. The move was accompanied by a shift of focus toward in situ measurements of highly charged ions, which continue with increased vigor. Overviews of the facility, which includes EBIT-I and SuperEBIT, and the research projects are given, including results from optical spectroscopy, QED, and X-ray line excitation measurements

[en] Recent measurements of the K-shell and L-shell x-ray spectra of highly charged helium-like and neonlike ions are presented that were performed on the Livermore electron beam ion traps and the Princeton tokamaks. These measurements provide new insights into collisional and indirect line formation processes, identifications of forbidden lines, and a new plasma line diagnostic of magnetic field strength

[en] We present measurements of the energy loss of relativistic highly charged uranium ions interacting with a target beam of near-liquid density hydrogen droplets at the experimental storage ring (ESR) at GSI. Our results reveal that a liquid droplet target beam virtually behaves like a homogeneous gas jet target with respect to both energy loss and ion beam cooling. We also provide first results on ion beam cooling efficiency at high hydrogen area target densities, which are consistent with numerical estimations based on a simple model of the cooling force.

[en] The population of magnetic sublevels in hydrogen-like uranium ions has been investigated in relativistic ion-atom collisions by observing the subsequent X-ray emission. Using the gas target at the experimental storage ring facility we observed the angular emission of Lyman-a radiation from hydrogen-like uranium ions. The alignment parameter for three different interaction energies was measured and found to agree well with theory. In addition, the use of different gas targets allowed for the electron-impact excitation process to be observed. (author)