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ABSTRACT: High quality absorption spectroscopy measurements were recently achieved at the Sandia National Laboratories Z facility in the soft x-ray range. Detailed spectral resolution knowledge is a key requirement for their interpretation. We present a methodology for measuring the wavelength dependent crystal spectral resolution, with a particular focus on the 7-17 Å range. We apply this procedure to the case of 1st order resolution of a potassium acid phthalate (KAP) convex crystal spectrometer. One calibration issue is that inferring the crystal resolution requires that the x-ray source emission feature widths and spectral profiles are known. To this aim, we resolve Manson x-ray source Si, Al, and Mg Kα line profiles using a KAP crystal spectrometer in 2nd order to achieve relatively high resolution. This information is exploited to measure 1st order KAP resolving powers λ∕Δλ∼1100-1300 in the 7-10 Å wavelength range.
The Review of scientific instruments 10/2012; 83(10):10E133. · 1.52 Impact Factor
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M R Gomez,
G A Rochau, J E Bailey,
G S Dunham,
M D Kernaghan,
P Gard,
G K Robertson,
A C Owen,
J W Argo,
D S Nielsen,
P W Lake
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ABSTRACT: The pinned optically aligned diagnostic dock (PODD) is a multi-configuration diagnostic platform designed to measure x-ray emission on the Z facility. The PODD houses two plasma emission acquisition (PEA) systems, which are aligned with a set of precision machined pins. The PEA systems are modular, allowing a single diagnostic housing to support several different diagnostics. The PEA configurations fielded to date include both time-resolved and time-integrated, 1D spatially resolving, elliptical crystal spectrometers, and time-integrated, 1D spatially resolving, convex crystal spectrometers. Additional proposed configurations include time-resolved, monochromatic mirrored pinhole imagers and arrays of filtered x-ray diodes, diamond photo-conducting diode detectors, and bolometers. The versatility of the PODD system will allow the diagnostic configuration of the Z facility to be changed without significantly adding to the turn-around time of the machine. Additionally, the PODD has been designed to allow instrument setup to be completed entirely off-line, leaving only a refined alignment process to be performed just prior to a shot, which is a significant improvement over the instrument the PODD replaces. Example data collected with the PODD are presented.
The Review of scientific instruments 10/2012; 83(10):10D714. · 1.52 Impact Factor
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ABSTRACT: Experiments have been performed at Sandia National Laboratories Z-facility to validate iron opacity models relevant to the solar convection/radiation zone boundary. Sample conditions were measured by mixing Mg with the Fe and using Mg K-shell line transmission spectra, assuming that the plasma was uniform. We develop a spectral model that accounts for hypothetical gradients, and compute synthetic spectra to quantitatively evaluate the plasma gradient size that can be diagnosed. Two sample designs are investigated, assuming linear temperature and density gradients. First, Mg uniformly mixed with Fe enables temperature gradients greater than 10% to be detected. The second design uses Mg mixed into one side and Al mixed into the other side of the sample in an attempt to more accurately infer the sample gradient. Both temperature and density gradients as small as a few percent can be detected with this design. Experiments have successfully recorded spectra with the second design. In future research, the spectral model will be used to place bounds on gradients that exist in Z opacity experiments.
The Review of scientific instruments 10/2012; 83(10):10E128. · 1.52 Impact Factor
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ABSTRACT: New, high spectral resolution X-ray observations from astrophysical photoionised plasmas have been recorded in recent years
by the Chandra and XMM-Newton orbiting telescopes. These observations provide a wealth of detailed information and have motivated
new efforts at developing a detailed understanding of the atomic kinetics and radiation physics of photoionised plasmas. The
Z facility at Sandia National Laboratories is a powerful source of X-rays that enables us to produce and study photoionised
plasmas in the laboratory under well characterised conditions. We discuss a series of radiation-hydrodynamic simulations to
help understand the X-ray environment, plasma hydrodynamics and atomic kinetics in experiments where a collapsing wire array
at Z is used as an ionising source of radiation to create a photoionised plasma. The numerical simulations are used to investigate
the role that the key experimental parameters have on the photoionised plasma characteristics.
KeywordsPhotoionised plasma–Modelling–Simulation–Hydrodynamics–Atomic-kinetics
Astrophysics and Space Science 04/2012; 336(1):189-194. · 1.69 Impact Factor
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I. M. Hall,
T. Durmaz,
R. C. Mancini, J. E. Bailey,
G. A. Rochau,
M. J. Rosenberg,
D. H. Cohen,
I. E. Golovkin,
J. J. MacFarlane,
M. E. Sherril,
J. Abdallah,
R. F. Heeter,
M. E. Foord,
S. H. Glenzer,
H. A. Scott
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ABSTRACT: Photoionised plasmas are common in astrophysical environments and new high resolution spectra from such sources have been
recorded in recent years by the Chandra and XMM-Newton satellites. These provide a wealth of spectroscopic information and
have motivated recent efforts aimed at obtaining a detailed understanding of the atomic-kinetic and radiative characteristics
of photoionised plasmas. The Z-pinch facility at the Sandia National Laboratories is the most powerful terrestrial source
of X-rays and provides an opportunity to produce photoionised plasmas in a well characterised radiation environment. We present
modelling work and experimental design considerations for a forthcoming experiment at Sandia in which X-rays from a collapsing
Z-pinch will be used to photoionise low density neon contained in a gas cell. View factor calculations were used to evaluate
the radiation environment at the gas cell; the hydrodynamic characteristics of the gas cell were examined using the Helios-CR
code, in particular looking at the heating, temperature and ionisation of the neon and the absorption of radiation. Emission
and absorption spectra were also computed, giving estimates of spectra likely to be observed experimentally.
Astrophysics and Space Science 04/2012; 322(1):117-121. · 1.69 Impact Factor
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B Jones,
C A Jennings, J E Bailey,
G A Rochau,
Y Maron,
C A Coverdale,
E P Yu,
S B Hansen,
D J Ampleford,
P W Lake,
G Dunham,
M E Cuneo,
C Deeney,
D V Fisher,
V I Fisher,
V Bernshtam,
A Starobinets,
L Weingarten
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ABSTRACT: The observation of Doppler splitting in K-shell x-ray lines emitted from optically thin dopants is used to infer implosion velocities of up to 70 cm/μs in wire-array and gas-puff Z pinches at drive currents of 15-20 MA. These data can benchmark numerical implosion models, which produce reasonable agreement with the measured velocity in the emitting region. Doppler splitting is obscured in lines with strong opacity, but red-shifted absorption produced by the cooler halo of material backlit by the hot core assembling on axis can be used to diagnose velocity in the trailing mass.
Physical Review E 11/2011; 84(5 Pt 2):056408. · 2.26 Impact Factor
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ABSTRACT: We discuss the processing of x-ray absorption spectra from photoionized plasma experiments at Z. The data was recorded with an imaging spectrometer equipped with two elliptically bent potassium acid phthalate (KAP) crystals. Both time-integrated and time-resolved data were recorded. In both cases, the goal is to obtain the transmission spectra for quantitative analysis of plasma conditions.
The Review of scientific instruments 10/2010; 81(10):10E324. · 1.52 Impact Factor
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ABSTRACT: We are attempting to measure the transmission of iron on Z at plasma temperatures and densities relevant to the solar radiation and convection zone boundary. The opacity data published by us to date has been taken at an electron density about a factor of 10 below the 9×10(22)/cm(3) electron density of this boundary. We present results of two-dimensional (2D) simulations of the heating and expansion of an opacity sample driven by the dynamic Hohlraum radiation source on Z. The aim of the simulations is to design foil samples that provide opacity data at increased density. The inputs or source terms for the simulations are spatially and temporally varying radiation temperatures with a Lambertian angular distribution. These temperature profiles were inferred on Z with on-axis time-resolved pinhole cameras, x-ray diodes, and bolometers. A typical sample is 0.3 μm of magnesium and 0.078 μm of iron sandwiched between 10 μm layers of plastic. The 2D LASNEX simulations indicate that to increase the density of the sample one should increase the thickness of the plastic backing.
The Review of scientific instruments 10/2010; 81(10):10E518. · 1.52 Impact Factor
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J. E. Bailey,
G. A. Rochau,
S. B. Hansen,
T. J. Nash,
D. S. Nielsen,
P. W. Lake,
C. A. Iglesias,
R. C. Mancini,
J. J. MacFarlane,
I. Golovkin,
P. Wang,
C. Blancard,
Ph. Cosse,
G. Faussurier,
F. Gilleron,
J. C. Pain,
J. Jr. Abdallah,
A. K. Pradhan,
S. N. Nahar
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ABSTRACT: Recent experiments extended iron opacity model tests to temperatures above 150 eV for the first time. The experiments use the Z Facility to volumetrically heat a CH-tamped Fe/Mg plasma using x-rays. The frequency dependent sample transmission is measured by viewing a backlight through the sample. The plasma conditions are inferred from the Mg K-shell absorption. The strategy for this research is to examine the underlying physics within Fe opacity models by comparisons with the measured transmission. Physics topics of interest include charge state distribution, energy level structure, and line broadening. In this talk we discuss methods to exploit the data and advance understanding for these topics. In addition, we review new experiments under way to further improve the data and to achieve higher energy density conditions.
AIP Conference Proceedings 09/2009; 1161(1).
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J E Bailey,
G A Rochau,
R C Mancini,
C A Iglesias,
J J MacFarlane,
I E Golovkin,
J C Pain,
F Gilleron,
C Blancard,
Ph Cosse,
G Faussurier,
G A Chandler,
T J Nash,
D S Nielsen,
P W Lake
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ABSTRACT: Understanding stellar interiors, inertial confinement fusion, and Z pinches depends on opacity models for mid-Z plasmas in the 100-300 eV temperature range. These models are complex and experimental validation is crucial. In this paper we describe the diagnosis of the first experiments to measure iron plasma opacity at a temperature high enough to produce the charge states and electron configurations that exist in the solar interior. The dynamic Hohlraum x-ray source at Sandia National Laboratories' Z facility was used to both heat and backlight Mg/Fe CH tamped foils. The backlighter equivalent brightness temperature was estimated to be T(r) approximately 314 eV+/-8% using time-resolved x-ray power and imaging diagnostics. This high brightness is significant because it overwhelms the sample self-emission. The sample transmission in the 7-15.5 A range was measured using two convex potassium acid phthalate crystal spectrometers that view the backlighter through the sample. The average spectral resolution over this range was estimated to be lambda/deltalambda approximately 700 by comparing theoretical crystal resolution calculations with measurements at 7.126, 8.340, and 12.254 A. The electron density was determined to be n(e)=6.9+/-1.7 x 10(21) cm(-3) using the Stark-broadened Mg Hebeta, Hegamma, and Hedelta lines. The temperature inferred from the H-like to He-like Mg line ratios was T(e)=156+/-6 eV. Comparisons with three different spectral synthesis models all have normalized chi(2) that is close to unity, indicating quantitative consistency in the inferred plasma conditions. This supports the reliability of the results and implies the experiments are suitable for testing iron opacity models.
The Review of scientific instruments 12/2008; 79(11):113104. · 1.52 Impact Factor
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G A Rochau, J E Bailey,
Y Maron,
G A Chandler,
G S Dunham,
D V Fisher,
V I Fisher,
R W Lemke,
J J Macfarlane,
K J Peterson,
D G Schroen,
S A Slutz,
E Stambulchik
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ABSTRACT: The Z-pinch dynamic hohlraum is an x-ray source for high energy-density physics studies that is heated by a radiating shock to radiation temperatures >200 eV. The time-dependent 300-400 eV electron temperature and 15-35 mg/cc density of this shock have been measured for the first time using space-resolved Si tracer spectroscopy. The shock x-ray emission is inferred from these measurements to exceed 50 TW, delivering >180 kJ to the hohlraum.
Physical Review Letters 03/2008; 100(12):125004. · 7.37 Impact Factor
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J E Bailey,
G A Rochau,
C A Iglesias,
J Abdallah,
J J Macfarlane,
I Golovkin,
P Wang,
R C Mancini,
P W Lake,
T C Moore,
M Bump,
O Garcia,
S Mazevet
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ABSTRACT: Measurements of iron-plasma transmission at 156+/-6 eV electron temperature and 6.9+/-1.7 x 10(21) cm(-3) electron density are reported over the 800-1800 eV photon energy range. The temperature is more than twice that in prior experiments, permitting the first direct experimental tests of absorption features critical for understanding solar interior radiation transport. Detailed line-by-line opacity models are in excellent agreement with the data.
Physical Review Letters 01/2008; 99(26):265002. · 7.37 Impact Factor
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G A Rochau, J E Bailey,
G A Chandler,
G Cooper,
G S Dunham,
P W Lake,
R J Leeper,
R W Lemke,
T A Mehlhorn,
A Nikroo,
K J Peterson,
C L Ruiz,
D G Schroen,
S A Slutz,
D Steinman,
W A Stygar,
W Varnum
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ABSTRACT: The Z-pinch dynamic hohlraum (ZPDH) is a high-power x-ray source that has been used in a variety of high energy-density experiments including inertial confinement fusion (ICF) studies. The system consists of a tungsten wire-array Z pinch that implodes onto a low-density CH2 foam converter launching a radiating shock that heats the hohlraum to radiation temperatures >200 eV. Through time-gated pinhole camera measurements, the mean shock speed is measured from 28 experiments to be 326 ± 4 µm ns−1 with a shot-to-shot standard deviation of 7%. Broad-band x-ray measurements indicate that the shot-to-shot reproducibility in the power emission and pulse-shape of the source shock is <15% and ~5%, respectively. Calculations have shown that an ICF capsule placed at the center of the foam in the ZPDH can absorb >40 kJ of x-ray energy, within a factor of 4 of the energy believed sufficient for ICF ignition. The capsule types imploded by the ZPDH have evolved over four years culminating in a design that produces record indirect-drive DD thermonuclear neutron yields of up to 3.5E11.
Plasma Physics and Controlled Fusion 11/2007; 49(12B):B591. · 2.42 Impact Factor
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ABSTRACT: Plasma spectroscopy requires determination of spectral line intensities and widths. At Sandia National Laboratories Z facility we use elliptical crystal spectrometers equipped with gated microchannel plate detectors to record time and space resolved spectra. We collect a large volume of data typically consisting of five to six snapshots in time and five to ten spectral lines with 30 spatial elements per frame, totaling to more than 900 measurements per experiment. This large volume of data requires efficiency in processing. We have addressed this challenge by using a line fitting routine to automatically fit each spectrum using assumed line profiles and taking into account photoelectron statistics to efficiently extract line intensities and widths with uncertainties. We verified that the random data noise obeys Poisson statistics. Rescale factors for converting film exposure to effective counts required for understanding the photoelectron statistics are presented. An example of the application of these results to the analysis of spectra recorded in Z experiments is presented.
Review of Scientific Instruments 07/2007; 78(6):063106. · 1.37 Impact Factor
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G. A. Rochau, J. E. Bailey,
G. A. Chandler,
T. J. Nash,
D. S. Nielsen,
G. S. Dunham,
O. F. Garcia,
N. R. Joseph,
J. W. Keister,
M. J. Madlener,
D. V. Morgan,
K. J. Moy,
M. Wu
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ABSTRACT: Understanding of microchannel plate (MCP) detectors with x-ray energy is important for applications in high energy density research such as broadband imaging and x-ray spectroscopy. The relative sensitivity with photon energy for Cu/Au coated MCPs in the range of 250 eV<hν<5000 eV has been measured at the National Synchrotron Light Source. A model of this response that includes contributions from secondary photoelectron yield and interactions with multiple channels is presented. This model is shown to agree with the measured MCP response to <20% over the majority of the spectral range using cross sections determined from an independent analysis of the MCP glass composition.
Review of Scientific Instruments 10/2006; 77(10):10E323-10E323-4. · 1.37 Impact Factor
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ABSTRACT: An on-axis time-resolved x-ray pinhole camera has been used on the 20 MA 100 ns driver Z to image the converging shock wave in dynamic Hohlraum experiments and to image pellet hot spots in inertial confinement fusion implosions. This instrument is susceptible to detecting significant amounts of pinch bremsstrahlung radiation with energies at hundreds of keV and yields of roughly 1 kJ. Quite often the bremsstrahlung noise signals have overwhelmed the desired x-ray images. In an effort to eliminate this large source of noise we have incorporated a 6° gold-coated grazing incidence mirror into the time-resolved x-ray pinhole camera system. The mirror reflects soft x rays at energies under 2 keV but does not reflect bremsstrahlung radiation at hundreds of keV. We will present data from the instrument without the mirror showing large amounts of bremsstrahlung noise contamination and data with the mirror in the system showing greatly reduced noise levels.
Review of Scientific Instruments 10/2006; 77(10):10E319-10E319-3. · 1.37 Impact Factor
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ABSTRACT: Elliptical crystal spectrometers equipped with time-gated microchannel plate (MCP) detectors provide time-, space-, and spectrally resolved data. A common problem is that the number of time resolution elements is limited by the number of MCP frames. The number of frames that fit on a given MCP is limited by the image size and the alignment tolerance. At the Z facility these problems have been addressed with twin-elliptical-crystal spectrometers. Using two crystals and detectors doubles the number of frames available. This enables measurements with ∼ 350 ps time resolution while still recording data from an ∼ 4 ns wide time window. Alternatively, the twin crystal design allows simultaneous measurements with different crystals to investigate different spectral regimes.
Review of Scientific Instruments 09/2006; 77(10):10F315-10F315-4. · 1.37 Impact Factor
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S. A. Slutz,
K. J. Peterson,
R. A. Vesey,
R. W. Lemke, J. E. Bailey,
W. Varnum,
C. L. Ruiz,
G. W. Cooper,
G. A. Chandler,
G. A. Rochau,
T. A. Mehlhorn
Physics of Plasmas 01/2006; 13:102701. · 2.15 Impact Factor
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ABSTRACT: We present results from simulations performed to investigate the effects of dopant radiative cooling in inertial confinement fusion indirect-drive capsule implosion experiments. Using a one-dimensional radiation-hydrodynamics code that includes inline collisional-radiative modeling, we compute in detail the non-local thermodynamic equilibrium atomic kinetics and spectral characteristics for Ar-doped DD fuel. Specifically, we present results from a series of calculations in which the concentration of the Ar is varied, and examine the sensitivity of the fuel conditions (e.g., electron temperature) and neutron yield to the Ar dopant concentration. Simulation results are compared with data obtained in OMEGA indirect-drive experiments in which monochromatic imaging and spectral measurements of Ar Hebeta and Lybeta line emission were recorded. The incident radiation drive on the capsule is computed with a three-dimensional view factor code using the laser beam pointings and powers from the OMEGA experiments. We also examine the sensitivity of the calculated compressed core electron temperatures and neutron yields to the radiation drive on the capsule and to the radiation and atomic modeling in the simulations.
Physical Review E 01/2006; 72(6 Pt 2):066403. · 2.26 Impact Factor
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ABSTRACT: High-power Z pinches on Sandia National Laboratories' Z facility can be used in a variety of experiments to radiatively heat samples placed some distance away from the Z-pinch plasma. In such experiments, the heating radiation spectrum is influenced by both the Z-pinch emission and the re-emission of radiation from the high-Z surfaces that make up the Z-pinch diode. To test the understanding of the amplitude and spectral distribution of the heating radiation, thin foils containing both Al and MgF2 were heated by a 100-130 TW Z pinch. The heating of these samples was studied through the ionization distribution in each material as measured by x-ray absorption spectra. The resulting plasma conditions are inferred from a least-squares comparison between the measured spectra and calculations of the Al and Mg 1s-->2p absorption over a large range of temperatures and densities. These plasma conditions are then compared to radiation-hydrodynamics simulations of the sample dynamics and are found to agree within 1sigma to the best-fit conditions. This agreement indicates that both the driving radiation spectrum and the heating of the Al and MgF2 samples is understood within the accuracy of the spectroscopic method.
Physical Review E 12/2005; 72(6 Pt 2):066405. · 2.26 Impact Factor
