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We report measurements of electron-impact excitation cross sections for the strong K-shell n=2-1 transitions in S XV using the LLNL EBIT-I electron beam ion trap, two crystal spectrometers, and the EBIT Calorimeter Spectrometer. The cross sections are determined by direct normalization to the well known cross sections of radiative electron capture, measured simultaneously. Using contemporaneous polarization measurements with the two crystal spectrometers, whose dispersion planes are oriented parallel and perpendicular to the electron beam direction, the polarization of the direct excitation line emission is determined, and in turn the isotropic total cross sections are extracted. We further experimentally investigate various line-formation mechanisms, finding that radiative cascades and collisional inner-shell ionization dominate the degree of linear polarization and total line-emission cross sections of the forbidden line $z$., 16 Pages, 9 Figures, published in ApJ

Based on laboratory data from the Lawrence Livermore EBIT-I electron beam ion trap and calculations using the relativistic multi-reference Moller-Plesset (MRMP) perturbation theory approach, we identify L-shell transitions of M-shell iron ions in emission spectra of the nearby stars Capella and Procyon. These lines are weaker than the well known, prominent lines from Fe XVII. However, they need to be taken into account when modeling the spectra, especially of cool stars.

We present absolute throughput analysis of several crystals for the Orion High-REsolution X-ray (OHREX) imaging crystal spectrometer using ray tracing and experimental measurements. The OHREX spectrometer is a high-resolution x-ray spectrometer designed to measure spectral line shapes at the Orion laser facility. The spectrometer is fielded with up to two spherical crystals simultaneously covering two independent spectral ranges. Each crystal has a nominal radius of curvature of R = 67.2 cm and is fielded at a nominal Bragg angle of 51.3°. To cover different bands of interest, several different crystals are available, including Ge (111), KAP, and several cuts of quartz, whose resolving power λ/Δλ exceeds 10 000. The calibrated response of the available crystals has previously been reported from measurements at the EBIT-I electron beam ion trap at Lawrence Livermore National Laboratory. Here, we model the absolute throughput of each crystal using ray tracing and verify the results using experimental data for the quartz (101¯1) crystal.

Prompted by the detection of K-shell absorption or emission features in the spectra of plasma surrounding high mass X-ray binaries and black holes, recent measurements using the Livermore electron beam ion trap have focused on the energies of the n = 2 to n = 1 K-shell transitions in the L-shell ions of lithiumlike through fluorinelike silicon and sulfur. In parallel, we have made calculations of these transitions using the Flexible Atomic Code and the multi-reference Moller-Plesset (MRMP) atomic physics code. Using this code we have attempted to produce sets of theoretical atomic data with spectroscopic accuracy for all the L-shell ions of silicon and sulfur. We present results of our calculations for oxygenlike and fluorinelike silicon and compare them to the recent electron beam ion trap measurements as well as previous calculations.

We have used an electron beam ion trap to measure electron-density-diagnostic line-intensity ratios for extreme ultraviolet lines from F XII, XIII, and XIV at wavelengths of 185-205 255-276 Angstroms. These ratios can be used as density diagnostics for astrophysical spectra and are especially relevant to solar physics. We found that density diagnostics using the Fe XIII 196.53/202.04 and the Fe XIV 264.79/274.21 and 270.52A/274.21 line ratios are reliable using the atomic data calculated with the Flexible Atomic Code. On the other hand, we found a large discrepancy between the FAC theory and experiment for the commonly used Fe XII (186.85 + 186.88)/195.12 line ratio. These FAC theory calculations give similar results to the data tabulated in CHIANTI, which are commonly used to analyze solar observations. Our results suggest that the discrepancies seen between solar coronal density measurements using the Fe XII (186.85 + 186.88)/195.12 and Fe XIII 196.54/202.04 line ratios are likely due to issues with the atomic calculations for Fe XII.

In an electron beam ion trap (EBIT), the ions are not confined to the electron beam, but rather oscillate in and out of the beam. As a result, the ions do not continuously experience the full density of the electron beam. To determine the effective electron density, ne,eff, experienced by the ions, the electron beam size, the nominal electron density ne, and the ion distribution around the beam, i.e., the so-called ion cloud, must be measured. We use imaging techniques in the extreme ultraviolet (EUV) and optical to determine these. The electron beam width is measured using 3d → 3p emission from Fe xii and xiii between 185 and 205 A. These transitions are fast and the EUV emission occurs only within the electron beam. The measured spatial emission profile and variable electron current yield a nominal electron density range of ne ∼ 1011–1013 cm−3. We determine the size of the ion cloud using optical emission from metastable levels of ions with radiative lifetimes longer than the ion orbital periods. The resulting emission maps out the spatial distribution of the ion cloud. We find a typical electron beam radius of ∼60 μm and an ion cloud radius of ∼300 μm. These yield a spatially averaged effective electron density, ne,eff, experienced by the ions in EBIT spanning ∼ 5 × 109–5 × 1011 cm−3.

The warm electron beam ion trap (WEBIT) at Lawrence Livermore National Laboratory is being developed as a pre-launch, ground calibration source for space-borne, high-throughput, high-resolution x-ray spectrometers, such as the x-ray imaging and spectroscopy mission Resolve quantum calorimeter. Historically, calibration sources for calorimeter spectrometers have relied on characteristic line emission from x-ray tubes, fluorescing metals, and radioactive sources. The WEBIT, by contrast, relies on emission from x-ray transitions in highly charged ions, for example, hydrogen-like and helium-like ions, whose energies are well known and whose line shapes are relatively simple. The WEBIT can create astrophysically relevant ions whose x-ray emission falls in the 0.3-12 keV science bandpass of Resolve and has a portable design advantageous for a calibration source. The WEBIT will be used to help calibrate Resolve’s instrumental line shape and gain scale as a function of various operational parameters during both detector subsystem level testing and instrumental level testing.

Uncertainties in atomic models will introduce noticeable additional systematics in calculating the flux of weak dielectronic recombination (DR) satellite lines, affecting the detection and flux measurements of other weak spectral lines. One important example is the Ar XVII He-beta DR, which is expected to be present in emission from the hot intracluster medium (ICM) of galaxy clusters and could impact measurements of the flux of the 3.5 keV line that has been suggested as a secondary emission from a dark matter interaction. We perform a set of experiments using the Lawrence Livermore National Laboratory's electron beam ion trap (EBIT-I) and the X-Ray Spectrometer quantum calorimeter (XRS/EBIT), to test the Ar XVII He-beta DR origin of the 3.5 keV line. We measured the X-ray emission following resonant DR onto helium-like and lithium-like Argon using EBIT-I's Maxwellian simulator mode at a simulated electron temperature of Te=1.74 keV. The measured flux of the Ar XVII He-beta DR lined is too weak to account for the flux in the 3.5 keV line assuming reasonable plasma parameters. We, therefore, rule out Ar XVII He-beta DR as a significant contributor to the 3.5 keV line. A comprehensive comparison between the atomic theory and the EBIT experiment results is also provided., Comment: Accepted for publication in ApJ. 11 pages, 5 figures

The Orion high-resolution X-ray (OHREX) imaging spherically bent crystal spectrometer, operated with both image plates and CCD cameras, provides time-averaged plasma diagnostics through high-resolution spectroscopy with good signal-to-noise at the Orion laser facility. In order to provide time-resolved spectra, the OHREX will be outfitted with a streak camera, and in this case, even higher signal to noise will be desired. Using the OHREX’s sister instrument, the EBIT High-resolution X-ray (EBHiX) spectrometer, at the LLNL electron beam ion trap EBIT-I, we therefore compare the efficiency of a high-quality Ge (111) crystal (2d = 6.532 A) with that of a higher integrated reflectivity, but lower-resolution highly annealed pyrolytic graphite (HAPG) crystal (2d = 6.708 A) in the energy range 2408–2452 eV. We find that the HAPG provides overall more signal across the entire image; however, because of the much better focusing properties of the Ge crystal, the latter provides more signal within the central 100 μm of the spatial profile in the cross-dispersion direction and is thus more suitable for the narrow entrance window of the Livermore-built streak camera.

We have designed and implemented a neutral metal vapor injector on the SuperEBIT high-energy electron beam ion trap at the Lawrence Livermore National Laboratory. A horizontally directed vapor of a europium metal is created using a thermal evaporation technique. The metal vapor is then spatially collimated prior to injection into the trap. The source's form and quantity constraints are significantly reduced making plasmas out of metal with vapor pressures ≤10(-7) Torr at ≥1000 °C more obtainable. A long pulsed or constant feed metal vapor injection method adds new flexibility by varying the timing of injection and rate of material being introduced into the trap.

We have used the EBIT-I electron beam ion trap at the Lawrence Livermore National Laboratory and a duplicate Orion High Resolution X-ray Spectrometer (OHREX) to measure the relative efficiency of a spherically bent quartz (101̄1) crystal (2d = 6.687 Å) and a spherically bent germanium (111) crystal (2d = 6.532 Å). L-shell X-ray photons from highly charged molybdenum ions generated in EBIT-I were simultaneously focussed and Bragg reflected by each crystal, both housed in a single spectrometer, onto a single CCD X-ray detector. The flux from each crystal was then directly compared. Our results show that the germanium crystal has a reflection efficiency significantly better than the quartz crystal, however, the energy resolution is significantly worse. Moreover, we find that the spatial focussing properties of the germanium crystal are worse than those of the quartz crystal. Details of the experiment are presented, and we discuss the advantages of using either crystal on a streak-camera equipped OHREX spectrometer.

X-ray spectroscopy is a useful tool for diagnosing plasma sources due to its non-invasive nature. One such source is the dense plasma focus (DPF). Recent interest has developed to demonstrate its potential application as a soft x-ray source. We present the first spectroscopic studies of krypton high energy density plasmas produced on a 3 kJ DPF device in Singapore. In order to diagnose spectral features, and to obtain a more comprehensive understanding of plasma parameters, a new non-local thermodynamic equilibrium L-shell kinetic model for krypton was developed. It has the capability of incorporating hot electrons, with different electron distribution functions, in order to examine the effects that they have on emission spectra. To further substantiate the validity of this model, it is also benchmarked with data gathered from experiments on the electron beam ion trap (EBIT) at Lawrence Livermore National Laboratory, where data were collected using the high resolution EBIT calorimeter spectrometer.

We report the calibration of the Orion High-Resolution X-ray (OHREX) imaging crystal spectrometer at the EBIT-I electron beam ion trap at Livermore. Two such instruments, dubbed OHREX-1 and OHREX-2, are fielded for plasma diagnostics at the Orion laser facility in the United Kingdom. The OHREX spectrometer can simultaneously house two spherically bent crystals with a radius of curvature of r = 67.2 cm. The focusing properties of the spectrometer allow both for larger distance to the source due to the increase in collected light and for observation of extended sources. OHREX is designed to cover a 2.5°–3° spectral range at Bragg angles around 51.3°. The typically high resolving powers at these large Bragg angles are ideally suited for line shape diagnostics. For instance, the nominal resolving power of the instrument (>10 000) is much higher than the effective resolving power associated with the Doppler broadening due to the temperature of the trapped ions in EBIT-I. The effective resolving power is only around 3000 at typical EBIT-I conditions, which nevertheless is sufficient to set up and test the instrument’s spectral characteristics. We have calibrated the spectral range for a number of crystals using well known reference lines in the first and second order and derived the ion temperatures from these lines. We have also made use of the 50 μm size of the EBIT-I source width to characterize the spatial focusing of the spectrometer.

We characterized the dissociation fraction of a thermal dissociation atomic hydrogen source by injecting the mixed atomic and molecular output of the source into an electron beam ion trap containing highly charged ions and recording the x-ray spectrum generated by charge exchange using a high-resolution x-ray calorimeter spectrometer. We exploit the fact that the charge exchange state-selective capture cross sections are very different for atomic and molecular hydrogen incident on the same ions, enabling a clear spectroscopic diagnostic of the neutral species.

We have developed a high-resolution x-ray spectrometer for measuring the shapes of spectral lines produced from laser-irradiated targets on the Orion laser facility. The instrument utilizes a spherically bent crystal geometry to spatially focus and spectrally analyze photons from foil or microdot targets. The high photon collection efficiency resulting from its imaging properties allows the instrument to be mounted outside the Orion chamber, where it is far less sensitive to particles, hard x-rays, or electromagnetic pulses than instruments housed close to the target chamber center in ten-inch manipulators. Moreover, Bragg angles above 50° are possible, which provide greatly improved spectral resolution compared to radially viewing, near grazing-incidence crystal spectrometers. These properties make the new instrument an ideal lineshape diagnostic for determining plasma temperature and density. We describe its calibration on the Livermore electron beam ion trap facility and present spectral data of the K-shell emission from highly charged sulfur produced by long-pulse as well as short-pulse beams on the Orion laser in the United Kingdom.

We present spectroscopic measurements of the M-shell emission of highly charged europium performed at the Livermore SuperEBIT electron beam ion trap facility using the EBIT Calorimeter Spectrometer (ECS). There is significant blending among the emission lines from the different charge states but despite the complexity of the observed spectra we have successfully identified the ten brightest n = 4 ? 3 transitions from sodium-like Eu52+ utilizing the Flexible Atomic Code (FAC). We find that the difference between the calculated and measured transition energies for these ten Eu52+ lines does not exceed 3 eV. In fact, for four of the identified lines we find agreement within the measured uncertainties. Additional comparison with semi-empirical transition-energy predictions for sodium-like ions from laser-generated plasmas is included and shows that overall the semi-empirical predicted values for the transition energies are slightly higher than the measured values, while the FAC values that didnt agree with the measured transition energies are almost 1 eV lower than the measured values.

A high-resolution grazing-incidence grating spectrometer has been implemented on the Livermore electron beam ion traps for performing very high-resolution measurements in the soft x-ray and extreme ultraviolet region spanning from below 10 Å to above 300 Å. The instrument operates without an entrance slit and focuses the light emitted by highly charged ions located in the roughly 50 μm wide electron beam onto a cryogenically cooled back-illuminated charge-coupled device detector. The measured line widths are below 0.025 Å above 100 Å, and the resolving power appears to be limited by the source size and Doppler broadening of the trapped ions. Comparisons with spectra obtained with existing grating spectrometers show an order of magnitude improvement in spectral resolution.

For over a decade, the x-ray astrophysics community has enjoyed a fruitful epoch of discovery largely as a result of the successful launch and operation of the high resolution, high sensitivity spectrometers on board the Chandra, XMM-Newton and Suzaku x-ray observatories. With the launch of the x-ray calorimeter spectrometer on the Astro-H x-ray observatory in 2014, the diagnostic power of high resolution spectroscopy will be extended to some of the hottest, largest and most exotic objects in our Universe. The diagnostic utility of these spectrometers is directly coupled to, and often limited by, our understanding of the x-ray production mechanisms associated with the highly charged ions present in the astrophysical source. To provide reliable benchmarks of theoretical calculations and to address specific problems facing the x-ray astrophysics community, electron beam ion traps have been used in laboratory astrophysics experiments to study the x-ray signatures of highly charged ions. A brief overview of the EBIT-I electron beam ion trap operated at Lawrence Livermore National Laboratory and the Max-Planck-Institut für Kernphysik's FLASH-EBIT operated at third and fourth generation advanced light sources, including a discussion of some of the results are presented.

Strong, relatively short, absorption dips have been observed in the x-ray light curves measured from the high mass x-ray binary system Cygnus X-1. With increasing strength of the dips, which are believed to be caused by 'clumps' of cold material present in the stellar wind of Cyg X-1's companion star, K-shell absorption lines in L-shell ions of Si and S develop. To determine the bulk motion of the clumps via the Doppler shifts of these lines with high accuracy, we measured their reference energies using the Lawrence Livermore National Laboratory electron beam ion trap EBIT-I and EBIT Calorimeter Spectrometer. Our findings—shifts consistent with zero velocity of the absorber throughout all ionization states at orbital phase zero—provide evidence for an onion-like ion structure of the clumps.