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Measurement of the temperature of cold highly charged ions produced in an electron beam ion trap

Description: The temperature of highly charged titanium ions produced and trapped in an electron beam ion trap was determined by precisely measuring the broadening of the emission line profile caused by the thermal Doppler motion. The measured temperature ranges from about 700 eV for deeply trapped ions to about 70 eV for ions in a shallow trap. The latter value represents the lowest temperature at which the x-ray emission of collisonally excited heliumlike Ti{sup 20}+ ions has ever been recorded, and the measured transitions represent the narrowest x-ray lines observed from highly charged titanium ions.
Date: September 14, 1994
Creator: Beiersdorfer, P.; Decaux, V. & Widmann, K.
Partner: UNT Libraries Government Documents Department

Uncertainty Analysis Technique for OMEGA Dante Measurements

Description: The Dante is an 18 channel X-ray filtered diode array which records the spectrally and temporally resolved radiation flux from various targets (e.g. hohlraums, etc.) at X-ray energies between 50 eV to 10 keV. It is a main diagnostics installed on the OMEGA laser facility at the Laboratory for Laser Energetics, University of Rochester. The absolute flux is determined from the photometric calibration of the X-ray diodes, filters and mirrors and an unfold algorithm. Understanding the errors on this absolute measurement is critical for understanding hohlraum energetic physics. We present a new method for quantifying the uncertainties on the determined flux using a Monte-Carlo parameter variation technique. This technique combines the uncertainties in both the unfold algorithm and the error from the absolute calibration of each channel into a one sigma Gaussian error function. One thousand test voltage sets are created using these error functions and processed by the unfold algorithm to produce individual spectra and fluxes. Statistical methods are applied to the resultant set of fluxes to estimate error bars on the measurements.
Date: May 7, 2010
Creator: May, M J; Widmann, K; Sorce, C; Park, H & Schneider, M
Partner: UNT Libraries Government Documents Department

Lifetime of the 1s2s 3S1 metastable level in He-like S14+ measured with an electron beam ion trap

Description: A precision measurement of the lifetime of the lowest exited level of the He-like S{sup 14+} ion carried out at the Livermore EBIT-II electron beam ion trap yielded a value of (703 {+-} 4) ns. Our method extends the range of lifetime measurements accessible with electron beam ion traps into the nanosecond region and improves the accuracy of currently available data for this level by an order of magnitude.
Date: March 16, 2006
Creator: L?pez-Urrutia, J C; Beiersdorfer, P & Widmann, K
Partner: UNT Libraries Government Documents Department

Spectroscopy at the high-energy electron beam ion trap (Super EBIT)

Description: The following progress report presents some of the x-ray measurements performed during the last year on the Livermore SuperEBIT facility. The measurements include: direct observation of the spontaneous emission of the hyperfine transition in ground state hydrogenlike holmium, {sup 165}Ho{sup 66{plus}}; measurements of the n {equals} 2 {r_arrow} 2 transition energies in neonlike thorium, Th{sup 80{plus}}, through lithiumlike thorium, Th{sup 87{plus}}, testing the predictions of quantum electrodynamical contributions in high-Z ions up to the 0.4{percent} level; measurements of the isotope shift of the n= 2 {r_arrow} 2 transition energies between lithiumlike through carbonize uranium, {sup 233}U{sup 89{plus}...86{plus}} and {sup 238}U{sup 89{plus}...86{plus}}, inferring the variation of the mean- square nuclear charge radius; and high-resolution measurements of the K{alpha} radiation of heliumlike xenon, Xe{sup 52 {plus}}, using a transmission-type crystal spectrometer, resolving for the first time the ls2p{sup 3}P{sub 1} {r_arrow} 1S{sup 2} {sup 1}S{sub 0} and ls2s{sup 3}S{sub 1} {r_arrow} 1S{sup 2} {sup 1}S{sub 0} transitions individually. 41 refs., 9 figs., 1 tab.
Date: July 10, 1996
Creator: Widmann, K.; Beiersdorfer, P. & Crespo Lopez-Urrutia, J.R.
Partner: UNT Libraries Government Documents Department

L-Shell Spectroscopy of Au as a Temperature Diagnostic Tool

Description: In order to develop plasma diagnostic for reduced-size hot hohlraums under laser irradiation, they have studied the L-shell emission from highly charged gold ions in the SuperEBIT electron beam ion trap. The resolving power necessary to identify emission features from individual charge states in a picket fence pattern has been estimated, and the observed radiation features have been compared with atomic structure calculations. They find that the strong 3d{sub 5/2} {yields} 2p{sub 3/2} emission features are particularly useful in determining the charge state distribution and average ion charge <Z>, which are strongly sensitive to the electron temperature.
Date: March 27, 2008
Creator: Trabert, E; Hansen, S B; Beiersdorfer, P; Brown, G V; Widmann, K & Chung, H K
Partner: UNT Libraries Government Documents Department

Time-Resolved Single-State Measurements of the Electronic Structure of Isochoric Heated Copper

Description: Time-resolved x-ray photoelectron spectroscopy is used to probe the non-steady-state evolution of the valence band electronic structure of laser heated ultra-thin (50 nm) Cu. Single-shot x-ray laser induced time-of-flight photoelectron spectroscopy with picosecond time resolution is used in conjunction with optical measurements of the disassembly dynamics that have shown the existence of a metastable liquid phase in fs-laser heated Cu foils persisting 4-5 ps. This metastable phase is studied using a 527 nm wavelength 400 fs laser pulse containing 0.1-2.5 mJ laser energy focused in a large 500 x 700 {micro}m{sup 2} spot to create heated conditions of 0.07-1.8 x 10{sup 12} W cm{sup -2} intensity. Valence band photoemission spectra showing the changing occupancy of the Cu 3d level with heating are presented. These are the first picosecond x-ray laser time-resolved photoemission spectra of laser-heated ultra-thin Cu foil showing changes in electronic structure. The ultrafast nature of this technique lends itself to true single-state measurements of shocked and heated materials.
Date: October 22, 2004
Creator: Nelson, A J; Dunn, J; Widmann, K; Ao, T; Ping, Y; Hunter, J et al.
Partner: UNT Libraries Government Documents Department

Optical Properties in Non-equilibrium Phase Transitions

Description: An open question about the dynamical behavior of materials is how phase transition occurs in highly non-equilibrium systems. One important class of study is the excitation of a solid by an ultrafast, intense laser. The preferential heating of electrons by the laser field gives rise to initial states dominated by hot electrons in a cold lattice. Using a femtosecond laser pump-probe approach, we have followed the temporal evolution of the optical properties of such a system. The results show interesting correlation to non-thermal melting and lattice disordering processes. They also reveal a liquid-plasma transition when the lattice energy density reaches a critical value.
Date: January 5, 2006
Creator: Ao, T; Ping, Y; Widmann, K; Price, D F; Lee, E; Tam, H et al.
Partner: UNT Libraries Government Documents Department

Advancements in time-resolved x-ray laser induced time-of-flight photoelectron spectroscopy

Description: Time-resolved soft x-ray photoelectron spectroscopy is used to probe the non-steady-state evolution of the valence band electronic structure of laser heated ultra-thin (50 nm) metal foils and bulk semiconductors. Single-shot soft x-ray laser induced time-of-flight photoelectron spectroscopy with picosecond time resolution was used in combination with optical measurements of the disassembly dynamics that have shown the existence of a metastable liquid phase in fs-laser heated metal foils persisting 4-5 ps. This metastable phase is studied using a 527 nm wavelength 400 fs laser pulse containing 0.3-2.5 mJ laser energy focused in a large 500 x 700 {micro}m{sup 2} spot to create heated conditions of 0.2-1.8 x 10{sup 12} W cm{sup -2} intensity. The unique LLNL COMET compact tabletop soft x-ray laser source provided the necessary high photon flux, highly monoenergetic, picosecond pulse duration, and coherence for observing the evolution of changes in the valence band electronic structure of laser heated metals and semiconductors with picosecond time resolution. This work demonstrates the continuing development of a powerful new technique for probing reaction dynamics and changes of local order on surfaces on their fundamental timescales including phenomena such as non-thermal melting, chemical bond formation, intermediate reaction steps, and the existence of transient reaction products.
Date: July 28, 2005
Creator: Nelson, A J; Dunn, J; Widmann, K; Ao, T; Ping, Y; Hunter, J et al.
Partner: UNT Libraries Government Documents Department

Investigation of the 2p3/2-3d5/2 line emission of Au53+ -- Au69+ for diagnosing high energy density plasmas

Description: 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 Au{sup 53+} through neonlike Au{sup 69+}. Using atomic data from the Flexible Atomic Code, we have identified strong 3d{sub 5/2} {yields} 2p{sub 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{sub 5/2} {yields} 2p{sub 3/2} emission features to plasma conditions, and investigate the effects of plasma density on calculated L-shell Au emission spectra.
Date: January 29, 2008
Creator: Brown, G V; Hansen, S B; Trabert, E; Beiersdorfer, P; Widmann, K; Chen, H et al.
Partner: UNT Libraries Government Documents Department

Uncharted Frontiers in the Spectroscopy of Highly Charged Ions

Description: The development of novel techniques is critical for maintaining a state-of-the-art core competency in atomic physics and readiness for evolving programmatic needs. We have carried out a three-year effort to develop novel spectroscopic instrumentation that added new dimensions to our capabilities for measuring energy levels, radiative transition probabilities, and electron-ion excitation processes. The new capabilities created were in areas that heretofore had been inaccessible to scientific scrutiny and included high-resolution spectroscopy of hard x rays, femtosecond lifetime measurements, measurements of transition probabilities of long-lived metastable levels, polarization spectroscopy, ultra-precise determinations of energy levels, and the establishment of absolute wavelength standards in x-ray spectroscopy. Instrumentation developed during the period included a transmission-type crystal spectrometer, a flat-field EUV spectrometer, and the development and deployment of absolutely calibrated monolithic crystals. The new capabilities enabled very sensitive tests of atomic wave functions, of calculations of magnetic sublevel populations, and of fundamental theories in uncharted regimes, and provided the basis for developing new diagnostic techniques of high-density plasmas.
Date: January 8, 2000
Creator: Beiersdorfer, P.; Brown, G.; Crespo, J.; Kim, S.-H.; Neill, P.; Utter, S. et al.
Partner: UNT Libraries Government Documents Department

Application of Spatially Resolved High Resolution Crystal Spectrometry to ICF Plasmas

Description: High resolution (λ/Δ#3;λ ~ 10 000) 1D imaging x-ray spectroscopy using a spherically bent crystal and a 2D hybrid pixel array detector is used world wide for Doppler measurements of ion-temperature and plasma flow-velocity profiles in magnetic confinement fusion plasmas. Meter sized plasmas are diagnosed with cm spatial resolution and 10 ms time resolution. This concept can also be used as a diagnostic of small sources, such as inertial confinement fusion plasmas and targets on x-ray light source beam lines, with spatial resolution of micrometers, as demonstrated by laboratory experiments using a 250-μm 55 Fe source, and by ray-tracing calculations. Throughput calculations agree with measurements, and predict detector counts in the range 10-8 -10-6 times source x-rays, depending on crystal reflectivity and spectrometer geometry. Results of the lab demonstrations, application of the technique to the National Ignition Facility (NIF), and predictions of performance on NIF will be presented.
Date: September 15, 2012
Creator: Hill, Kenneth W.; Bitter, M.; Delgado-Aprico, L.; Pablant, N. A.; Beirersdorfer, P.; Schneider, M. et al.
Partner: UNT Libraries Government Documents Department

Observations of Plasmons in Warm Dense Matter

Description: We present the first collective x-ray scattering measurements of plasmons in solid-density plasmas. The forward scattering spectra of a laser-produced narrow-band x-ray line from isochorically heated beryllium show that the plasmon frequency is a sensitive measure of the electron density. Dynamic structure calculations that include collisions and detailed balance match the measured plasmon spectrum indicating that this technique will enable new applications to determine the equation of state and compressibility of dense matter.
Date: September 5, 2006
Creator: Glenzer, S H; Landen, O L; Neumayer, P; Lee, R W; Widmann, K; Pollaine, S W et al.
Partner: UNT Libraries Government Documents Department

Energetics of Multiple-Ion Species Hohlraum Plasmas

Description: A study of the laser-plasma interaction processes in multiple-ion species plasmas has been performed in plasmas that are created to emulate the plasma conditions in indirect drive inertial confinement fusion targets. Gas-filled hohlraums with densities of xe22/cc are heated to Te=3keV and backscattered laser light is measured by a suite of absolutely calibrated backscatter diagnostics. Ion Landau damping is increased by adding hydrogen to the CO2/CF4 gas fill. We find that the backscatter from stimulated Brillouin scattering is reduced is monotonically reduced with increasing damping, demonstrating that Landau damping is the controlling damping mechanism in ICF relevant high-electron temperature plasmas. The reduction in backscatter is accompanied by a comparable increase in both transmission of a probe beam and an increased hohlraum radiation temperature, showing that multiple-ion species plasmas improve the overall hohlraum energetics/performance. Comparison of the experimental data to linear gain calculations as well as detailed full-scale 3D laser-plasma interaction simulations show quantitative agreement. Our findings confirm the importance of Landau damping in controlling backscatter from high-electron temperature hohlraum plasmas and have lead to the inclusion of multi-ion species plasmas in the hohlraum point design for upcoming ignition campaigns at the National Ignition Facility.
Date: November 5, 2007
Creator: Neumayer, P; Berger, R; Callahan, D; Divol, L; Froula, D; London, R et al.
Partner: UNT Libraries Government Documents Department

Temperature Determination Using K(alpha) Spectra from M-shell Ti Ions

Description: The Compact Multipulse Terawatt (COMET) laser facility at LLNL was used to irradiate Al-coated 2 - 50 {micro}m Ti foils with {approx} 4 x 10{sup 18} W cm{sup -2}, 500 fs, 3-6 J laser pulses. Laser-plasma interactions on the front side of the target generate hot electrons with sufficient energy to excite inner-shell electrons in Ti, creating K{sub {alpha}} emission which has been measured using a focusing spectrometer with spatial resolution (FSSR-1D) aimed at the back surface of the targets. The spatial extent of the emission varies with target thickness, and the high spectral resolution ({lambda}/{Delta}{lambda} {approx} 3800) is sufficient to measure blue shifts in K{sub {alpha}} arising from ionization of near-solid Ti into the 3p subshell. A self-consistent-field model is used to spectroscopically diagnose thermal electron temperatures up to 40 eV in the strongly coupled Ti plasmas.
Date: March 24, 2005
Creator: Hansen, S B; Faenov, A Y; Pikuz, T A; Fournier, K B; Shepherd, R; Chen, H et al.
Partner: UNT Libraries Government Documents Department

Short Pulse Laser Absorption and Energy Partition at Relativistic Laser Intensities

Description: We have performed experiments at the COMET and Calisto short pulse laser facilities to make the first comprehensive measurements of the laser absorption and energy partition in solid targets heated with an ultrashort laser pulse focused to relativistic laser intensities (>10 10{sup 17} W/cm{sup 2}). The measurements show an exceedingly high absorption for P polarized laser-target interactions above 10{sup 19} W/cm{sup 2}. Additionally, the hot electron population is observed to markedly increase at the same intensity range. An investigation of the relaxation process was initiated u using time sing time-resolved K{sub {alpha}} spectroscopy. Measurements of the time time-resolved K{sub {alpha}} radiation suggest a 10-20 ps relativistic electron relaxation time. However modeling difficulties of these data are apparent and a more detailed investigation on this subject matter is warranted.
Date: February 27, 2007
Creator: Shepherd, R; Chen, H; Ping, Y; Dyer, G; Wilks, S; Chung, H et al.
Partner: UNT Libraries Government Documents Department

Measurement of the relaxation time of hot electrons in laser-solid interaction at relativistic laser intensities

Description: The authors have measured the relaxation time of hot electrons in short pulse laser-solid interactions using a picosecond time-resolved x-ray spectrometer and a time-integrated electron spectrometer. Employing laser intensities of 10{sup 17}, 10{sup 18}, and 10{sup 19} W/cm{sup 2}, they find increased laser coupling to hot electrons as the laser intensity becomes relativistic and thermalization of hot electrons at timescales on the order of 10 ps at all laser intensities. They propose a simple model based on collisional coupling and plasma expansion to describe the rapid relaxation of hot electrons. The agreement between the resulting K{sub {alpha}} time-history from this model with the experiments is best at highest laser intensity and less satisfactory at the two lower laser intensities.
Date: August 22, 2006
Creator: Chen, H; Shepherd, R; Chung, H K; Dyer, G; Faenov, A; Fournier, K B et al.
Partner: UNT Libraries Government Documents Department

Laboratory astrophysics and atomic physics using the NASA/GSFC microcalorimeter spectrometers at the LLNL Electron Beam Ion Trap and Radiation Properties Facility

Description: The 32 pixel laboratory microcalorimeter spectrometer built by the NASA/Goddard Space Flight Center is now an integral part of the spectroscopy suite used routinely by the electron beam ion trap and radiative properties group at the Lawrence Livermore National Laboratory. The second generation laboratory instrument, dubbed the XRS/EBIT, is nearly identical to the XRS instrument on the Suzaku X-ray Observatory, formerly Astro-E2. The detector array is from the same processed wafer and uses the same HgTe absorbers. it is being used to measure the photon emission from a variety of radiation sources. These include x-ray emission from laboratory simulated celestial sources, x-ray emission from highly charged ions of Au, and x-ray emission following charge exchange and radiative electron capture. The wide range of applications demonstrates the versatility of a high-resolution, high-efficiency low temperature detector that is able to collect data continually with minimal operator servicing.
Date: August 18, 2005
Creator: Brown, G; Beiersdorfer, P; Boyce, K; Chen, H; Gu, M F; Kahn, S et al.
Partner: UNT Libraries Government Documents Department

Development of a Time-resolved Soft X-ray Spectrometer for Laser Produced Plasma Experiments

Description: A 2400 line/mm variable spaced grating spectrometer (VSG) has been used to measure soft x-ray emission (8-22 {angstrom}) from laser-produced plasma experiments at Lawrence Livermore National Laboratory's Compact Multipulse Terrawatt (COMET) Laser Facility. The spectrometer was coupled to a Kentech x-ray streak camera to study the temporal evolution of soft x-rays emitted from the back of mylar and copper foils irradiated at 10{sup 15} W/cm{sup 2}. The instrument demonstrated a resolving power of {approx} 120 at 19 {angstrom} with a time resolution of 31 ps. The time-resolved copper emission spectrum was consistent with a photodiode monitoring the laser temporal pulse shape and indicated that the soft x-ray emission follows the laser heating of the target. The time and spectral resolution of this diagnostic make it useful for studies of high temperature plasmas.
Date: May 12, 2010
Creator: Cone, K. V.; Dunn, J.; Schneider, M. B.; Baldis, H. A.; Brown, G. V.; Emig, J. et al.
Partner: UNT Libraries Government Documents Department

Rapid, Absolute Calibration of X-ray Filters Employed By Laser-Produced Plasma Diagnostics

Description: The electron beam ion trap (EBIT) facility at the Lawrence Livermore National Laboratory is being used to absolutely calibrate the transmission efficiency of X-ray filters employed by diodes and spectrometers used to diagnose laser-produced plasmas. EBIT emits strong, discrete monoenergetic lines at appropriately chosen X-ray energies. X-rays are detected using the high-resolution EBIT calorimeter spectrometer (ECS), developed for LLNL at the NASA/Goddard Space Flight Center. X-ray filter transmission efficiency is determined by dividing the X-ray counts detected when the filter is in the line of sight by those detected when out of the line of sight. Verification of filter thickness can be completed in only a few hours, and absolute efficiencies can be calibrated in a single day over a broad range from about 0.1 to 15 keV. The EBIT calibration lab has been used to field diagnostics (e.g., the OZSPEC instrument) with fully calibrated X-ray filters at the OMEGA laser. Extensions to use the capability for calibrating filter transmission for the DANTE instrument on the National Ignition Facility are discussed.
Date: May 11, 2008
Creator: Brown, G. V.; Beiersdorfer, P.; Emig, J.; Frankel, M.; Gu, M. F.; Heeter, R. F. et al.
Partner: UNT Libraries Government Documents Department

Laboratory astrophysics: Measurements of n = n{prime} to n = 2 line emission in Fe{sup 16+} to Fe{sup 23+}

Description: One of the dominant forms of astronomical line emission in the 6 {angstrom} to 18 {angstrom} spectral region is line emission produced by n = n{prime} to n = 2 transitions in Fe{sup 16+} to Fe{sup 23+} (i.e., Fe L-shell n-2 line emission). Using the Lawrence Livermore National Laboratory electron beam ion trap (EBIT) facility, the authors have carried out a number of measurements designed to address astrophysical issues concerning Fe L-shell line emission. Desired ions are produced and trapped using the nearly monoenergetic electron beam of EBIT. Trapped ions are collisionally excited and the resulting X-ray line emission detected using Bragg crystal spectrometers. They have recently completed a line survey of Fe L-shell 3-2 line emission. The line survey will allow a more reliable accounting of line blending in astronomical spectra. They have now begun a series of broadband, high resolution line ratio measurements. These measurements are designed to benchmark atomic calculations used in astronomical plasma emission codes and also for comparison with X-ray spectral observations of astronomical objects. Initial measurements have been carried out in Fe{sup 23+}. Preliminary results agree with distorted wave calculations to within 20% and better.
Date: March 5, 1996
Creator: Savin, D.W.; Beiersdorfer, P.; Lopez-Urrutia, J.C.; Decaux, V.; Liedahl, D.A.; Reed, K.J. et al.
Partner: UNT Libraries Government Documents Department