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[en] As part of a project to complete a comprehensive catalogue of astrophysically relevant emission lines in support of new-generation X-ray observatories using the Lawrence Livermore electron beam ion traps EBIT-I and EBIT-II, we studied emission lines of argon and sulfur in the soft X-ray and extreme ultraviolet region. Here we present observations of Ar IX through Ar XVI and S VII through S XIV between 20 and 75 (angstrom) to illustrate our work
[en] As part of a larger project to complete a comprehensive catalogue of astrophysically relevant emission lines in support of new-generation X-ray observatories using the Lawrence Livermore electron beam ion traps EBIT-I and EBIT-II, the authors present observations of sulfur lines in the soft X-ray and extreme ultraviolet regions. The database includes wavelength measurements with standard errors, relative intensities, and line assignments for 127 transitions of S VII through S XIV between 20 and 75 (angstrom). The experimental data are complemented with a full set of calculations using the Hebrew University Lawrence Livermore Atomic Code (HULLAC). A comparison of the laboratory data with Chandra measurements of Procyon allows them to identify S VII-S XI lines
[en] We discovered a class of lines that are sensitive to the strength of the ambient magnetic field, and present a measurement of such a line in Ar IX near 49 (angstrom). Calculations show that the magnitude of field strengths that can be measured ranges from a few hundred gauss to several tens of kilogauss depending on the particular ion emitting the line
[en] We are continuing EBIT measurements of line lists in the EUV region for use as astrophysical diagnostics and have recently measured the same transitions in much denser plasma of the NSTX tokamak. This allows us to calibrate density-sensitive line ratios at their upper limits. We compare our observations at low and high density with calculations from the Flexible Atomic Code
[en] Laboratory measurements of the n = 3 to n = 3 emission from M-shell iron ions are presented and compared to synthetic spectra from the CHIANTI spectral model. The measurements cover the range 170-290 Å and are made at an electron density of about 1011 cm–3. Emission from Fe VIII through Fe XVI has been identified. Excellent agreement with CHIANTI predictions is found for most lines. Twenty weaker features are noted in the laboratory data that are either absent in CHIANTI or have recently been added and correspond to lines that have not been verified by experimental measurements. A few of these lines may have already been observed (but not yet identified) in the Sun. The features are attributed to emission from various charge states of iron, notably Fe IX and Fe XIII, and two features have been identified as transitions in Fe VIII, i.e., the 3p63d 2D5/2-3p 53d22P3/2 and the 3p 63d 2D3/2-3p 53d22P1/2 transitions at 225.25 ± 0.12 and 226.35 ± 0.10 Å, respectively. Seven lines in Fe XI, Fe XII, and Fe XIII between 200 and 205 Å are noted for which the wavelengths in the CHIANTI database disagree with those in the current database of the National Institute of Standards and Technology. Our measurements of five of these lines appear to agree with the assignments used in CHIANTI.
[en] The line ratios of the 2p-3d transitions in the B-like spectra Ar XIV and Fe XXII have been measured using the electron beam ion traps at Livermore. Radiative-collisional model calculations show these line ratios to be sensitive to the electron density in the ranges ne = 1010 to 1012 cm-3 and ne = 1013 to 1015 cm-3, respectively. In our experiment, the electron beam density of about 1011 cm-3 was varied by about a factor of 5. Our data show a density effect for the line doublet in Ar XIV, and good agreement with theory is found. The relative intensity of the Fe XXII doublet shows good agreement with our predicted low density limit. The N VI K-shell spectrum was used to infer the actual electron density in the overlap region of ion cloud and electron beam, and systematic measurements and calculations of this spectrum are presented as well. The Ar XIV and Fe XXII spectra promise to be reliable density diagnostics for stellar coronae, complementing the K-shell diagnostics of helium-like ions
[en] We measured wavelengths and intensities of L-shell emission lines of aluminum in the extreme ultraviolet wavelength band. We identify 75 features of Al IV through Al XI between 40 and 170 A. The strongest features are due to 3 → 2 transitions; features from 4 → 2, 5 → 2, and 6 → 2 transitions are also included. Calculations made with the Flexible Atomic Code using the configuration-interaction method and many-body perturbation theory are presented and compared to the experimental results.
[en] We describe upgrades to a compact grazing-incidence spectrometer utilized on the National Spherical Torus Experiment for monitoring light and heavy impurities. A fast-readout charge couple device camera has been implemented that allows the recording of spectra with up to 25 ms time integration. This capability is used to study the time evolution of the K-shell emission of hydrogenlike and heliumlike boron, carbon, nitrogen, and oxygen between 10 and 65 A. Different camera positioning pieces have been employed to extend the possible spectral range to as high as 140. Several lines that cannot be ascribed to the usual elements found in the plasma have been observed in this spectral range, although often only in a few isolated discharges.
[en] A compact grazing-incidence spectrometer has been implemented on the National Spherical Torus Experiment for spectral measurements in the 6-65 A ring spectral region. The spectrometer employed a 2400l/mm grating designed for flat-field focusing and a cryogenically cooled charge-coupled device camera for readout. The instrument was tested by recording the K-shell lines of boron, carbon, nitrogen, and oxygen, as well the L-shell lines from argon, iron, and nickel that fall into this spectral band. The observed linewidth was about 0.1 A ring , which corresponds to a resolving power of 400 for the C V lines. A temporal resolution as fast as 50 ms was obtained
[en] We present a spectrum of the Sun taken by the Cosmic Hot Interstellar Plasma Spectrometer (CHIPS) covering 150 to 275 A. This spectrum is dominated in the 200 A region by emission lines from intermediate charge states of iron (Fe VIII - FeXVI). We also made laboratory measurements of iron emission at temperatures relevant to solar emission on the EBIT-II electron beam ion trap and the Large Helical Device stellarator. We used our laboratory measurements to identify lines and check the CHIANTI database and then used CHIANTI to validate line identifications in the CHIPS spectrum.