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in creator/contributor: "Gu, M.F."

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Measurement and Modeling of Inner-Shell Satellites of Na-like Fe XVI between 14.5 �A and 18 �A

We have used the University of California Lawrence Livermore National Laboratory's EBIT-I electron beam ion trap to perform measurements of the wavelengths and relative intensities of the X-ray lines from inner-shell satellite transitions in sodium-like Fe XVI. The measurements were carried out with high-resolution crystal and grating spectrometers and covered the 14.5-18 {angstrom} wavelength band. Contrary to predicted line strengths and positions found in the literature, our results show tha… more

Date: September 10, 2007

Creator: Graf, A; Beiersdorfer, P; Brown, G V & Gu, M F

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Laboratory Calibration of Density-Dependent Lines in the EUV and Soft X-Ray Regions

We analyzed spectral data of Fe XXII and Ar XIV from laboratory sources in which the electron density varies by several orders of magnitude to help benchmark density-sensitive emission lines useful for astrophysics and to test the atomic models underlying the diagnostic line ratios. We found excellent agreement for Fe XXII, but poorer agreement for Ar XIV. A number of astrophysically important emission lines are sensitive to electron density in the EUV and soft X-ray regions. Lines from Fe XXII… more

Date: December 9, 2010

Creator: Lepson, J K; Beiersdorfer, P; Gu, M F & Desai, P

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Hybrid atomic models for spectroscopic plasma diagnostics

We propose a hybrid approach to treating atomic structure and rates in collisional-radiative models, combining the completeness of highly averaged models with the accuracy of detailed models. The hybrid scheme supplements a small subset of coronally accessible fine structure levels with a complete set of configuration- and superconfiguration-averaged levels and produces spectra based on transitions among a mix of fine-structure and relativistic configuration-averaged levels. Convenient expressi… more

Date: November 17, 2006

Creator: Hansen, S B; Bauche, J; Bauche-Arnoult, C & Gu, M F

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Polarization measurement of Iron L-shell lines on EBIT-I

We report measurements of the line polarization of Ne-like and F-like of iron n=3 to n=2 transitions in the x-ray region. We used the ''two-crystal technique'' developed in previous polarization measurements in our laboratory. Preliminary results from our measurements are presented together with the theoretical calculations using the Flexible Atomic Code (FAC). Our calculations show that contributions from cascades play an important role in the polarization calculations of most of the transitio… more

Date: March 3, 2004

Creator: Chen, H.; Beiersdorfer, P.; Robbins, D.; Smith, A. J. & Gu, M. F.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Laboratory Measurements of 3 --> 2 X-ray Line Ratios of F-like Fe XVIII and Ni XX

The intensity ratios of 3 {yields} 2 emission lines of Fe XVIII and Ni XX were measured on the Livermore electron beam ion trap (EBIT-I) with a flat-field grating spectrometer. The results were compared with distorted-wave (DW) calculations obtained with the Flexible Atomic Code and recent close-coupling calculations using the R-matrix code. The measured 3s {yields} 2p/3d {yields} 2p ratios are about 20-40% higher than the theoretical values. When more extended configuration interaction is incl… more

Date: March 8, 2007

Creator: Gu, M F; Chen, H; Brown, G V; Beiersdorfer, P & Kahn, S M

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Atomic Models for Motional Stark Effects Diagnostics

We present detailed atomic physics models for motional Stark effects (MSE) diagnostic on magnetic fusion devices. Excitation and ionization cross sections of the hydrogen or deuterium beam traveling in a magnetic field in collisions with electrons, ions, and neutral gas are calculated in the first Born approximation. The density matrices and polarization states of individual Stark-Zeeman components of the Balmer {alpha} line are obtained for both beam into plasma and beam into gas models. A det… more

Date: July 26, 2007

Creator: Gu, M F; Holcomb, C; Jayakuma, J; Allen, S; Pablant, N A & Burrell, K

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Laboratory Measurements of the Line Emission from Mid-Z L-Shell Ions in the EUV

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.

Date: May 2, 2006

Creator: Lepson, J K; Beiersdorfer, P; Chen, H; Gu, M F & Kahn, S M

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Laboratory measurements of high-n iron L-shell x-ray lines

We present a comprehensive wavelength survey of Fe L-shell X-ray lines between 7 and 11 {angstrom} measured using flat crystal spectrometers and the EBIT-I and EBIT-II electron beam ion traps at the Lawrence Livermore National Laboratory. This survey includes all significant emission lines produced by over 200 n {yields} 2 transitions in Fe XIX-XXIV, with n = 4-10. The identification and assignment of transitions are made with the help of detailed theoretical modeling using the Flexible Atomic … more

Date: September 5, 2006

Creator: Chen, H; Gu, M F; Behar, E; Brown, G V; Kahn, S M & Beiersdorfer, P

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Comparison of observed and theoretical Fe L emission from CIE plasmas

We analyze data from the Lawrence Livermore National Lab (LLNL) Electron Beam Ion Trap (EBIT) that simulates a CIE plasma by sweeping the electron beam to approximate a Maxwellian velocity distribution. These results are compared to spectra of confirmed astronomical CIE plasmas (e.g. outer regions of x-ray clusters) observed by XMM/RGS. We utilize the Photon Clean Method (PCM) to quantify these spectra (EBIT and XMM/RGS) in the form of ratios of Fe L lines in the emission complex near 1 keV. Th… more

Date: November 8, 2007

Creator: Carpenter, M; Beiersdorfer, P; Brown, G V; Chen, H C; Gu, M F & Jernigan, J G

Item Type: Report

Partner: UNT Libraries Government Documents Department

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Flat-Field Grating Spectrometer for High-Resolution Soft X-Ray and EUV Measurements on an Electron Beam Ion Trap

A R = 44.3 m grazing-incidence grating spectrometer has been implemented on the Livermore electron beam ion traps for high-resolution measurements in the soft x-ray and extreme ultraviolet region spanning from below 10 Angstrom up to 50 Angstrom. The instrument uses a grating with variable line spacing (about 2400 l/mm) for a flat field of view. Spectra are recorded with a back-illuminated charge-coupled device detector. The new instrument greatly improves upon the resolution achieved with exis… more

Date: March 27, 2004

Creator: Beiersdorfer, P.; Magee, E.; Trabert, E.; Chen, H.; Lepson, J. K.; Gu, M. F. et al.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Experimental and theoretical evaluation of density sensitive N VII, Ar XIV and Fe XXII line ratios

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 = 10{sup 10} to 10{sup 12} cm{sup -3} and ne = 10{sup 13} to 10{sup 15} cm{sup -3}, respectively. In our experiment, the electron beam density of about 10{sup 11} cm{sup -3} was varied by about a factor of 5. Our data show a dens… more

Date: January 9, 2004

Creator: Chen, H; Beiersdorfer, P; Heeter, L A; Liedahl, D A; Naranjo-Rivera, K L; Trabert, E et al.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Laboratory measurements of resonant contributions to Fe XXIV line emission

A number of X-ray astronomy satellites are scheduled for launch in the next few years. The Advanced X-ray Astrophysics Facility (AXAF) is scheduled for launch in 1998, and the X-Ray Multi-mirror Mission (XMM) and Astro-E in 1999. These satellites will carry spectrometers with resolving powers in the Fe L-shell emission region over an order of magnitude greater than the spectrometers aboard A CA. Interpreting AXAF, XMM, Astro-E spectra will require atomic data at an accuracy significantly greate… more

Date: October 27, 1997

Creator: Gu, M.F.; Beiersdorfer, P.; Brown, G.V.; Kahn, S.M.; Liedahl, D.A.; Reed, K.J. et al.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Atomic data for the ITER Core Imaging X-ray Spectrometer

The parameters of the ITER core plasmas will be measured using the Core Imaging X-ray Spectrometer (CIXS), a high-resolution crystal spectrometer focusing on the L-shell spectra of highly ionized tungsten atoms. In order to correctly infer the plasma properties accurate atomic data are required. Here, some aspects of the underlying physics are discussed using experimental data and theoretical predictions from modeling.

Date: June 15, 2012

Creator: Clementson, J.; Beiersdorfer, P.; Biedermann, C.; Bitter, M.; Delgado-Aparicio, L. F.; Graf, A. et al.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Identification of L-Shell Transitions in M-shell Iron Ions in the Spectra of Capella and Procyon

No Description Available.

Date: August 16, 2012

Creator: Lepson, J K; Beiersdorfer, P; Brown, G V; Trabert, E; Bode, M P; Desai, P et al.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Laboratory Measurements of 3 -> 2 X-ray Emission Lines of Ne-like Ni

The intensity ratios between 3 {yields} 2 emission lines in Ni XIX were measured on the Livermore electron beam ion trap (EBIT-I) with a flat-field grating spectrometer and the NASA/GSFC X-ray microcalorimeter. The results are consistent with earlier measurements of Fe XVII and other Ne-like ions at Livermore, and confirm the problems in the atomic modeling of the direct collisional excitation for Ne-like systems.

Date: March 18, 2004

Creator: Gu, M F; Beiersdorfer, P; Brown, G V; Chen, H; Boyce, K R; Kelley, R L et al.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Excitation Cross Section Measurement for n=3 to n=2 Line Emission in Fe{sup 20+} to Fe{sup 23+}

Electron impact excitation cross sections have been measured for iron L-shell 3 {yields} 2 lines of FeXXI to FeXXIV at the EBIT-II electron beam ion trap using a crystal spectrometer and a 6 x 6-element array microcalorimeter. The cross sections were determined by direct normalization to the well established cross section of radiative electron capture and a summary of calculated energy dependent radiative recombination cross sections for electron capture into the ground state fine structure lev… more

Date: August 25, 2004

Creator: Chen, H; Beiersdorfer, P; Scofield, J; Brown, G; Boyce, K; Kelley, R L et al.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Electron Impact Excitation Cross Section Measurement for n=3 to n=2 Line Emission in Fe17+ to Fe23+

We have measured the electron impact excitation cross sections for the strong iron L-shell 3 {yields} 2 lines of Fe XVIII to Fe XXIV at the EBIT-I electron beam ion trap using a crystal spectrometer and NASA-Goddard Space Flight Centers 6 x 6 pixel array microcalorimeter. The cross sections were determined by direct normalization to the well established cross section of radiative electron capture through a sophisticated model analysis which results in the excitation cross section for the strong… more

Date: April 20, 2006

Creator: Chen, H; Beiersdorfer, P; Brown, G V; Scofield, J; Gu, M F; Kahn, S M et al.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

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

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… more

Date: January 29, 2008

Creator: Brown, G V; Hansen, S B; Trabert, E; Beiersdorfer, P; Widmann, K; Chen, H et al.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Excitation Cross Section Measurement for n=3 to n=2 Line Emission in Fe17+ to Fe23+

The authors report the measurement of electron impact excitation cross sections for the strong iron L-shell 3 {yields} 2 lines of Fe XVIII through Fe XXIV at the EBIT-I electron beam ion trap using a crystal spectrometer and a 6 x 6 pixel array microcalorimeter. The cross sections were determined by direct normalization to the well established cross section of radiative electron capture through a sophisticated model analysis which results in the excitation cross section for 48 lines at multiple… more

Date: February 8, 2006

Creator: Chen, H; Gu, M F; Beiersdorfer, P; Boyce, K R; Brown, G V; Kahn, S M et al.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Laboratory Data for X-Ray Astronomy

Laboratory facilities have made great strides in producing large sets of reliable data for X-ray astronomy, which include ionization and recombination cross sections needed for charge balance calculations as well as the atomic data needed for interpreting X-ray line formation. We discuss data from the new generation sources and pay special attention to the LLNL electron beam ion trap experiment, which is unique in it's ability to provide direct laboratory access to spectral data under precisely… more

Date: March 2, 2000

Creator: Beiersdorfer, P.; Brown, G.V.; Chen, H.; Gu, M.F.; Kahn, S.M.; Lepson, J.K. et al.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

New Benchmarks from Tokamak Experiments for Theoretical Calculations of the Dielectronic Satellite Spectra of Helium-like Ions

Dielectronic satellite spectra of helium-like argon, recorded with a high-resolution X-ray crystal spectrometer at the National Spherical Torus Experiment, were found to be inconsistent with existing predictions resulting in unacceptable values for the power balance and suggesting the unlikely existence of non-Maxwellian electron energy distributions. These problems were resolved with calculations from a new atomic code. It is now possible to perform reliable electron temperature measurements a… more

Date: August 29, 2003

Creator: Bitter, M.; Gu, M.F.; Vainshtein, L.A.; Beiersdorfer, P.; Bertschinger, G.; Marchuk, O. et al.

Item Type: Report

Partner: UNT Libraries Government Documents Department

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Laboratory measurements of the x-ray line emission from neon-like Fe XVII

The authors have conducted a systematic study of the dominant x-ray line emission from Fe XVII. These studies include relative line intensities in the optically thin limit, intensities in the presence of radiation from satellite lines from lower charge states of iron, and the absolute excitation cross sections of some of the strongest lines. These measurements were conducted at the Lawrence Livermore National Laboratory electron beam ion trap facility using crystal spectrometers and a NASA-Godd… more

Date: April 28, 2006

Creator: Brown, G V; Beiersdorfer, P; Chen, H; Scofield, J; Boyce, K R; Kelley, R L et al.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

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

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 s… more

Date: August 18, 2005

Creator: Brown, G.; Beiersdorfer, P.; Boyce, K.; Chen, H.; Gu, M. F.; Kahn, S. et al.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Passive Spectroscopy Bolometers, Grating- And X-Ray Imaging Crystal Spectrometers

This tutorial gives a brief introduction into passive spectroscopy and describes the working principles of bolometers, a high-resolution grating spectrometer, and a novel X-ray imaging crystal spectrometer, which is of particular interest for profile measurements of the ion temperature and plasma rotation velocity on ITER and future burning plasma experiments.

Date: November 7, 2007

Creator: Bitter, M.; Hill, K. W.; Scott, S.; Paul, S.; Ince-Cushmann, A.; Reinke, M. et al.

Item Type: Article

Partner: UNT Libraries Government Documents Department