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Simulations of the radiation-flow within a silica-aerogel target

Description: We propose to field a series of experiments to study the flow of radiation through silica-aerogel targets. The soft x-rays are generated by the Z-machine at Sandia National Laboratories. We have completed simulations of the experiments using 2-D Lagrangian and Eulerian codes. The results of the calculations for one of the targets are presented here.
Date: January 1, 2002
Creator: Aubrey, J. B. (Joysree B.); Wood, B. P. (Blake P.); Peterson, D. L. (Darrell L.) & Kyrala, George A.
Partner: UNT Libraries Government Documents Department

Real space soft x-ray imaging at 10 nm spatial resolution

Description: Using Fresnel zone plates made with our robust nanofabrication processes, we have successfully achieved 10 nm spatial resolution with soft x-ray microscopy. The result, obtained with both a conventional full-field and scanning soft x-ray microscope, marks a significant step forward in extending the microscopy to truly nanoscale studies.
Date: April 24, 2011
Creator: Chao, Weilun; Fischer, Peter; Tyliszczak, T.; Rekawa, Senajith; Anderson, Erik & Naulleau, Patrick
Partner: UNT Libraries Government Documents Department

Observation of coupled vortex gyrations by 70-ps-time and 20-nm-space- resolved full-field magnetic transmission soft x-ray microscopy

Description: We employed time-and space-resolved full-field magnetic transmission soft x-ray microscopy to observe vortex-core gyrations in a pair of dipolar-coupled vortex-state Permalloy (Ni{sub 80}Fe{sub 20}) disks. The 70 ps temporal and 20 nm spatial resolution of the microscope enabled us to simultaneously measure vortex gyrations in both disks and to resolve the phases and amplitudes of both vortex-core positions. We observed their correlation for a specific vortex-state configuration. This work provides a robust and direct method of studying vortex gyrations in dipolar-coupled vortex oscillators.
Date: September 1, 2010
Creator: Jung, Hyunsung; Yu, Young-Sang; Lee, Ki-Suk; Im, Mi-Young; Fischer, Peter; Bocklage, Lars et al.
Partner: UNT Libraries Government Documents Department

Application of soft x-ray laser interferometry to study large-scale-length, high-density plasmas

Description: We have employed a Mach-Zehnder interferometer, using a Ne-like Y x- ray laser at 155 {Angstrom} as the probe source, to study large-scale- length, high-density colliding plasmas and exploding foils. The measured density profile of counter-streaming high-density colliding plasmas falls in between the calculated profiles using collisionless and fluid approximations with the radiation hydrodynamic code LASNEX. We have also performed simultaneous measured the local gain and electron density of Y x-ray laser amplifier. Measured gains in the amplifier were found to be between 10 and 20 cm{sup {minus}1}, similar to predictions and indicating that refraction is the major cause of signal loss in long line focus lasers. Images showed that high gain was produced in spots with dimensions of {approximately} 10 {mu}m, which we believe is caused by intensity variations in the optical drive laser. Measured density variations were smooth on the 10-{mu}m scale so that temperature variations were likely the cause of the localized gain regions. We are now using the interferometry technique as a mechanism to validate and benchmark our numerical codes used for the design and analysis of high-energy-density physics experiments. 11 refs., 6 figs.
Date: May 1, 1996
Creator: Wan, A.S.; Barbee, T.W., Jr. & Cauble, R.
Partner: UNT Libraries Government Documents Department

Detecting EUV transients in near real time with ALEXIS

Description: The Array of Low Energy X-ray Imaging Sensors (ALEXIS) experiment consists of a mini-satellite containing six wide angle EUV/ultrasoft X-ray telescopes (Priedhorsky et al. 1989, and Bloch et al. 1994). Its scientific objective is to map out the sky in three narrow ({Delta}E/E {approx} 5%) bandpasses around 66, 71, and 93 eV. During each 50 second satellite rotation period the six telescopes, each with a 30{degrees} field, of:view and a spatial resolution of 0.25{degrees}, scan most of the antisolar hemisphere of the sky. The project is a collaborative effort between Los Alamos National Laboratory, Sandia National Laboratory, and the University of California-Berkeley Space Sciences Laboratory. It is controlled entirely from a small ground station located at Los Alamos. The mission was launched on a Pegasus Air Launched Vehicle on April 25, 1993. An incident at launch delayed our ability to properly analyze the data until November of 1994. In January of 1995, we brought on line automated software to routinely carry out the transient search. After the data is downlinked from the satellite, the software processes and transforms it into sky maps that are automatically searched for new sources. The software then sends the results of these searches by e-mail to the science team within two hours of the downlink. This system has successfully detected the Cataclysmic Variables VW Hyi, U Gem and AR UMa in outburst, and has detected at least two unidentified short duration EUV transients (Roussel-Dupre et al 1995, Roussel-Dupre 1995).
Date: December 31, 1995
Creator: Roussel-Dupre`, D.; Bloch, J.J.; Theiler, J.; Pfafman, T. & Beauchesne, B.
Partner: UNT Libraries Government Documents Department

EUVE spectroscopy of polars

Description: An admittedly pedantic but hopefully useful and informative analysis is presented of the <I>EUVE</I> 70-180 Å spectra of nine polars. These spectra are fit with three different models - a blackbody, a pure-H stellar atmosphere, and a solar abundance stellar atmosphere|to reveal the presence of spectral features such as absorption lines and edges, and to investigate the sensitivity of the derived (<i>kT, N</i><sub>H</sub>, solid angle) and inferred (fractional emitting area, bolometric luminosity) parameters to the model assumptions. Among the models tested, the blackbody model best describes the observed spectra, although the untested irradiated solar abundance stellar atmosphere model is likely a better overall description of the EUV/soft X-ray spectra
Date: October 13, 1998
Creator: Mauche, C W
Partner: UNT Libraries Government Documents Department

Interface reaction characterization and interfacial effects in multilayers

Description: The performance of multilayer structures as x-ray, soft x-ray and extreme ultraviolet optics is dependent on the nature of the interfaces between constituent layers. Interfacial structure and the interaction between atoms at interfaces have also been demonstrated to have significant impact on the physical properties of multilayer materials in general and thus on their performance in other applied areas. As short summary of the approaches to characterization of interfaces in multilayer structures is presented as background. Two new techniques for the experimental evaluation of interfacial structure and interfacial structure effects are then considered and examples presented. Model calculations for one of these techniques which support the experimental results are also presented. In conclusion these results are reviewed of and an assessment of their implications relative to multilayer development given.
Date: April 1, 1998
Creator: Barbee, T.W., Jr. LLNL
Partner: UNT Libraries Government Documents Department

Evaluation of 1024 channel VUV-photo-diodes for soft x-ray diagnostic applications

Description: We tested the operation of 1024 channel diode arrays (Model AXUV-1024, from IRD, Inc.) in subdued room light to establish that they worked and to determine the direction and speed of the scan of the 1024 channels. Further tests were performed in vacuum in the HAP, High-Average-Power Facility. There we found that the bare or glass covered diodes detected primarily visible light as expected, but diodes filtered by aluminized parylene, produced a signal consistent with soft x-rays. It is probable that the spectral response and sensitivity, as discussed below, reproduce that previously demonstrated by 1 to 16 channel VUV-photodiodes; however, significantly more effort would be required to establish that experimentally. These detectors appear to be worth further evaluation where 25 w spatial resolution bolometers or spectrograph detectors of known sensitivity are required, and single-shot or 0.02-0.2s time response is adequate. (Presumably, faster readout would be available with custom drive circuitry.)
Date: April 25, 1997
Creator: Molvik, A. W.
Partner: UNT Libraries Government Documents Department

Soft X-ray Imaging

Description: The contents of this report cover the following: (1) design of the soft x-ray telescope; (2) fabrication and characterization of the soft x-ray telescope; and (3) experimental implementation at the OMEGA laser facility.
Date: May 20, 1999
Creator: Seely, John
Partner: UNT Libraries Government Documents Department

Ultra high resolution soft x-ray tomography

Description: Ultra high resolution three dimensional images of a microscopic test object were made with soft x-rays using a scanning transmission x-ray microscope. The test object consisted of two different patterns of gold bars on silicon nitride windows that were separated by {approximately}5{mu}m. A series of nine 2-D images of the object were recorded at angles between {minus}50 to +55 degrees with respect to the beam axis. The projections were then combined tomographically to form a 3-D image by means of an algebraic reconstruction technique (ART) algorithm. A transverse resolution of {approximately}1000 {Angstrom} was observed. Artifacts in the reconstruction limited the overall depth resolution to {approximately}6000 {Angstrom}, however some features were clearly reconstructed with a depth resolution of {approximately}1000 {Angstrom}. A specially modified ART algorithm and a constrained conjugate gradient (CCG) code were also developed as improvements over the standard ART algorithm. Both of these methods made significant improvements in the overall depth resolution bringing it down to {approximately}1200 {Angstrom} overall. Preliminary projection data sets were also recorded with both dry and re-hydrated human sperm cells over a similar angular range.
Date: July 19, 1995
Creator: Haddad, W.S.; Trebes, J.E. & Goodman, D.M.
Partner: UNT Libraries Government Documents Department

A soft x-ray undulator for the U5 beamline at NSLS

Description: The magnetic structure and spectral properties of a 7.5-cm, 30-period hybrid undulator are described. The device will be installed at the U5 port of the VUV storage ring at Brookhaven National Laboratory and will be a tunable source of very high brilliance soft x-ray radiation over the range of 13 from approximately 150 eV.
Date: October 1, 1988
Creator: Viccaro, P. J.; Shenoy, G. K.; Kim, S. H. & Bader, S. D.
Partner: UNT Libraries Government Documents Department

An elliptically-polarizing undulator with phase adjustable energy and polarization

Description: The authors present a planar helical undulator designed to produce elliptically polarized light. Helical magnetic fields may be produced by a variety of undulators with four parallel cassettes of magnets. In their design, all cassettes are mounted in two planes on slides so that they may be moved parallel to the electron beam. This allows the undulator to produce x-rays of left- or right-handed elliptical or circular polarization as well as horizontal or vertical linear polarization. In model calculations, they have found that by sliding the top pair of rows with respect to the bottom pair, or the left pair with respect to the right pair, they retain the polarization setting but change the magnetic field strength, and hence the x-ray energy. This allows them to select both energy and polarization by independent phase adjustments alone, without changing the gap between the rows. Such a design may be simpler to construct than an adjustable gap machine. The authors present calculations that model its operation and its effects on an electron beam.
Date: August 1, 1993
Creator: Lidia, S. & Carr, R.
Partner: UNT Libraries Government Documents Department

The Evolution of Ga and As Core Levels in the Formation of Fe/GaAs(001): A High Resolution Soft X-ray Photoelectron Spectroscopic Study

Description: A high resolution soft x-ray photoelectron spectroscopic study of Ga and As 3d core levels has been conducted for Fe/GaAs (001) as a function of Fe thickness. This work has provided unambiguous evidence of substrate disrupting chemical reactions induced by the Fe overlayer--a quantitative analysis of the acquired spectra indicates significantly differing behavior of Ga and As during Fe growth, and our observations have been compared with existing theoretical models. Our results demonstrate that the outdiffusing Ga and As remain largely confined to the interface region, forming a thin intermixed layer. Whereas at low coverages Fe has little influence on the underlying GaAs substrate, the onset of substrate disruption when the Fe thickness reaches 3.5 {angstrom} results in major changes in the energy distribution curves (EDCs) of both As and Ga 3d cores. Our quantitative analysis suggests the presence of two new As environments of metallic character; one bound to the interfacial region and another which, as confirmed by in-situ oxidation experiments, surface segregates and persists over a wide range of overlayer thickness. Analysis of the corresponding Ga 3d EDCs found not two, but three new environments--also metallic in nature. Two of the three are interface-resident whereas the third undergoes outdiffusion at low Fe coverages. Based on the variations of the integrated intensities of each component, we present a schematic of the proposed chemical make-up of the Fe/GaAs (001) system.
Date: December 8, 2006
Creator: Thompson, J W; Neal, J R; Shen, T H; Morton, S A; Tobin, J G; Waddill, G D et al.
Partner: UNT Libraries Government Documents Department

Soft x-ray shock loading and momentum coupling in meteorite and planetary materials.

Description: X-ray momentum coupling coefficients, C{sub M}, were determined by measuring stress waveforms in planetary materials subjected to impulsive radiation loading from the Sandia National Laboratories Z-machine. Results from the velocity interferometry (VISAR) diagnostic provided limited equation-of-state data as well. Targets were iron and stone meteorites, magnesium rich olivine (dunite) solid and powder ({approx}5--300 {mu}m), and Si, Al, and Fe calibration targets. All samples were {approx}1 mm thick and, except for Si, backed by LiF single-crystal windows. The x-ray spectrum included a combination of thermal radiation (blackbody 170--237 eV) and line emissions from the pinch material (Cu, Ni, Al, or stainless steel). Target fluences 0.4--1.7 kJ/cm{sup 2} at intensities 43--260 GW/cm{sup 2} produced front surface plasma pressures 2.6--12.4 GPa. Stress waves driven into the samples were attenuating due to the short ({approx}5 ns) duration of the drive pulse. Attenuating wave impulse is constant allowing accurate C{sub M} measurements provided mechanical impedance mismatch between samples and the window are known. Impedance-corrected C{sub M} determined from rear-surface motion was 1.9--3.1 x 10{sup -5} s/m for stony meteorites, 2.7 and 0.5 x 10{sup -5} s/m for solid and powdered dunite, 0.8--1.4 x 10{sup -5}.
Date: December 1, 2010
Creator: Lawrence, R. Jeffery; Remo, John L. & Furnish, Michael David
Partner: UNT Libraries Government Documents Department

Magnetic-Field Sensitive Line Ratios in EUV and Soft X-ray Spectra

Description: 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.
Date: April 24, 2006
Creator: Beiersdorfer, P; Scofield, J; Brown, G V; Chen, H; Trabert, E & Lepson, J K
Partner: UNT Libraries Government Documents Department

Surface Slope Metrology on Deformable Soft X-ray Mirrors

Description: We report on the current state of surface slope metrology on deformable mirrors for soft x-rays at the Advanced Light Source (ALS). While we are developing techniques for in situ at-wavelength tuning, we are refining methods of ex situ visible-light optical metrology to achieve sub-100-nrad accuracy. This paper reports on laboratory studies, measurements and tuning of a deformable test-KB mirror prior to its use. The test mirror was bent to a much different optical configuration than its original design, achieving a 0.38 micro-radian residual slope error. Modeling shows that in some cases, by including the image conjugate distance as an additional free parameter in the alignment, along with the two force couples, fourth-order tangential shape errors (the so-called bird shape) can be reduced or eliminated.
Date: January 31, 2010
Creator: Yuan, Sheng; Yashchuk, Valeriy V.; Goldberg, Kenneth A.; Celestre, Rich; Church, Matthew; McKinney, Wayne R. et al.
Partner: UNT Libraries Government Documents Department

Running Shanghai Soft x-ray FEL with the EEHG scheme

Description: With the nominal beam parameters (beam energy: 0.84 GeV, slice energy spread: 168 keV, peak current: 600 A, normalized emittance: 2 mm mrad) of the Shanghai soft X-ray Free Electron Laser (SXFEL) project, we show that using the echo-enabled harmonic generation (EEHG) scheme, 9 nm coherent soft x-ray with peak power exceeding 400 MW can be generated directly from the 270 nm seeding laser.
Date: December 18, 2008
Creator: Xiang, D. & Stupakov, G.
Partner: UNT Libraries Government Documents Department

SOFT X-RAY FEL BY CASCADING STAGES OF HIGH GAIN HARMONIC GENERATION.

Description: Short wavelength Free-Electron Lasers are perceived as the next generation of synchrotron light sources. In the past decade, significant advances have been made in the theory and technology of high brightness electron beams and single pass FELs. These developments facilitate the construction of practical VUV FELs and make x-ray FELs possible. Self-Amplified Spontaneous Emission (SASE) and High Gain Harmonic Generation (HGHG)[17-19] are the two leading candidates for x-ray FELs. The first lasing of HGHG proof-of-principle experiment succeeded in August, 1999 in Brookhaven National Laboratory. The experimental results agree with the theory prediction. Compared with SASE FEL, the following advantages of HGHG FEL were confirmed; (1) Better longitudinal coherence, and hence, much narrower bandwidth than SASE. (2) More stable central wavelength, (3) More stable output energy. In this introduction, we will first briefly describe the principle of HGHG in Section A. Then in Section B, we give a general description about how to produce soft x-ray by cascading HGHG scheme. In section 2, we give a detailed description of the system design. Then, in section 3, we give a description of an analytical estimate for the HGHG process, and the calculation of the parameters of different parts of the system. The estimate is found to agree with simulation within about a factor 2 for most cases we studied. The stability issue, the sensitivity to parameter variation, the harmonic contents of the final output, and the noise degradation issue of such HGHG scheme are discussed in Section 4. The results are presented in Section 4. Finally, in Section 5, we will give some discussion of the challenges in development of the system. The conclusion is given in Section 6.
Date: April 17, 2003
Creator: YU,L.H.
Partner: UNT Libraries Government Documents Department

Site-specific, synchrotron radiation induced surface photochemistry

Description: This paper discusses recent research directed at understanding the nature of surface photochemistry driven by soft x-ray synchrotron radiation (SR). The research is motivated by the potential of x-rays for both high spatial resolution and site specificity. Although a number of systems indicate the potential for site specificity, the authors chose to study the system of SiF{sub 4}/Ge because the adsorbate`s photoabsorption spectrum is rich in structure near the Si 2p threshold (106 eV) while that of the substrate is structureless. This allows them to differentiate substrate-induced effects from those of the adsorbate. By performing time-dependent measurements of the changes induced in the photoemission spectra by SR, they have found that this system`s photochemistry is site-specific in the Si 2p region and have also determined the nature of the products produced by the reaction.
Date: December 31, 1995
Creator: Rosenberg, R.A.; Simons, J.K. & Frigo, S.P.
Partner: UNT Libraries Government Documents Department

Changing mass liner system for generation of soft X-radiation

Description: This report is issued in compliance with Clause F.4.2 of Contract 4769M0014-9Y ``Design study for X-ray generation``. In the first report (Clause F.4.1 of Contract) three systems were considered to solve the formulated problem. All of them were designed on the basis of employment of {O}400 mm disk explosive-magnetic generators (DEMG) as an energy source using a high-speed (25--30 cm/{micro}s) liner converging to the axis. The considered systems differs in modes of current pulse formation. For further effort the customer has chosen System 3 with the changing mass liner. In accordance with this fact this report discusses basic theoretical and computational results obtained to date for System 3. Further development of the theory of the considered system is suggested in the context of the series of experiments the ultimate goal of which is to generate soft X-radiation. Basic stages of the effort to generate soft X-radiation are discussed on the basis of the schedule given with consideration of some corrections which occurred when the system type had been selected.
Date: December 31, 1994
Creator: Mokhov, V.N.; Buyko, A.M.; Burenkov, O.M.; Garanin, S.F.; Startsev, A.I. & Yakubov, V.B.
Partner: UNT Libraries Government Documents Department

Soft x-ray spectroscopy measurements of plasma conditions at early times in ICF experiments on OMEGA. Semi-annual report, November 1, 1998--April 30, 1999

Description: Since arrival of FY-99 funding in December, the authors have been preparing for the first series of experiments under this grant on the OMEGA laser facility, which just took place (for one day) on April 27, 1999. The campaign was successful and results will be included in the next progress report following analyses. For the first time, they fielded their Ten Inch Manipulator (TIM-) mounted flat-field, grazing-incidence extreme-ultraviolet (euv) spectrograph with a four-channel gated-stripline microchannel plate (MCP) detector. This spectrograph covers the spectral range of 30--250 {angstrom} (hv = 50--400 eV). As in a previous campaign of May 1998, where the authors used this instrument with time-integrated photographic recording, the spectrograph reached closer to the target than did the previous version mounted on the chamber wall; such that the sensitivity increased by at least a factor-of-10 for viewing weak spectral features. The analysis during this reporting period of the euv spectroscopic results from the October 1998 NLUF/OMEGA campaign of Mg X, XI and XII spectra from n = 3 to n = 2 transitions are shown in Fig. 1 versus time. The data plotted represent a composite between the three most sensitive striplines, delayed relative to each other, for a number of shots. The intended emphasis was on the early portion of the event while the laser intensity is rising to a peak. This measured euv history agrees with that from the x-ray streak spectrographic data shown in Fig. 2 from the same campaign, i.e., the peak period of emission being in the first 1.5 ns.
Date: May 3, 1999
Creator: Griem, H.R. & Elton, R.C.
Partner: UNT Libraries Government Documents Department