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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

Optical diagnostics on ETA-II for x-ray spot size

Description: Improvements have been made in the performance of the ETA-II accelerator that allow a nominal 2 kA, 6 MeV beam to be focused to a spot size less that 1 mm in diameter. The improvements include reducing the energy sweep to less than +/- 0.5 & over 40 ns of the pulse using a real time energy diagnostic and improving the magnetic tune of the accelerator to reduce the emittance to 8 cm-mrad. Finally, an automated tuning system (MAESTRO) was run to minimize the time dependent centroid motion (corkscrew) by adjusting the steering dipoles over the focusing solenoids. The corkscrew motion was reduced to less than +/- 0.5 mm at the output of the accelerator.
Date: March 22, 1999
Creator: Richardson, R A
Partner: UNT Libraries Government Documents Department

Current and ultimate limitations of scanning x-ray nanotomography.

Description: X-ray nanotomography has developed into a powerful new tool for three-dimensional structural analysis. The scanning approach offers capabilities that are competitive with full-field imaging. Current and ultimate limitations of nanotomography are examined in light of recent work.
Date: February 6, 2002
Creator: McNulty, I.
Partner: UNT Libraries Government Documents Department


Description: Eleven papers are included of which nine were separately abstracted. The remaining two papers appear in NSA; one, on dimensional changes in U during irradiation, appears in Voh. 15, abstract no. 4341, and the other, on x ray preferred orientation, appears in Vol. 14, abstract no. 19415. (J.R.D.)
Date: May 1, 1961
Creator: Mueller, M.H. ed.
Partner: UNT Libraries Government Documents Department


Description: We discuss the temporal and spectral properties of self-amplified spontaneous emission (SASE) utilizing an energy-chirped electron beam. A short temporal pulse is generated by using a monochromator to select a narrow radiation bandwidth from the frequency chirped SASE. For the filtered radiation, the minimum pulse length is limited by the intrinsic SASE bandwidth, while the number of modes and the energy fluctuation can be controlled through the monochromator bandwidth. Two cases are considered: (1) placing the monochromator at the end of a single long undulator; (2) placing the monochromator after an initial undulator and amplifying the short-duration output in a second undulator. We analyze these cases and show that tens of femtosecond x-ray pulses may be generated for the linac coherent light source.
Date: January 7, 2004
Partner: UNT Libraries Government Documents Department

High-resolution imaging of early-time imprinting using normal-incidence multilayer mirrors. Final report

Description: A normal-incidence multilayer mirror telescope was designed, fabricated, and tested. The telescope consisted of a primary mirror and a secondary mirror in a Cassegrain optical configuration. The mirrors had multilayer coatings that efficiently reflected the soft x-ray radiation in a narrow bandpass centered at a wavelength of 48 {angstrom}. The telescope was taken to the Laboratory for Laser Energetics (LLE) on October 28, 1996. The telescope was mounted in a TIM instrument module on the OMEGA target chamber. The focusing and alignment of the mirrors were checked and optimized. Images were recorded on x-ray film on October 30. Images were recorded on a gated framing camera on October 31 and November 1. On each laser shot, hard x-ray images were recorded by a pinhole camera and a gated framing camera. The soft and hard x-ray images were returned to NRL for analysis. The images were digitized and compared. The major result of the study was that the soft x-ray emission from plasmas generated by 6 to 8 overlapping OMEGA beams is quite uniform, even for the case when beam smoothing techniques were not implemented. This implies that the soft x-ray emission can be used for backlighter applications and for the study of absorption by CH foils in the 48 {angstrom} wavelength region, at slightly longer wavelengths than the carbon K absorption edge where carbon is relatively transmissive. These backlighter techniques are now being implemented at LLE.
Date: May 1, 1998
Creator: Seely, J.F.
Partner: UNT Libraries Government Documents Department

CDF results on diffraction from Run I and plans for Run II

Description: Results on soft and hard diffraction obtained by the CDF Collaboration in Run I of the Fermilab Tevatron {bar p}p collider are reviewed and compared with results from the DESY ep collider HERA and with theoretical expectations. In addition, the CDF program for diffractive studies in Run II is briefly reviewed with emphasis on the relevant detector upgrades and physics goals.
Date: October 16, 2001
Creator: Goulianos, K.
Partner: UNT Libraries Government Documents Department

Specular and diffuse reflection of soft x-rays from mirrors

Description: Measurements of surface scattering from plane mirrors with different degrees of roughness using soft x-rays are reported. Angle resolved distributions of s-polarized light, scattered in the plane of incidence, were obtained with a precise reflectometer for various angles of incidence and different wavelengths. The influence of the sample preparation and the optical constants on the scattering properties is shown.
Date: August 1, 1985
Creator: Hogrefe, H.; Haelbich, R.P. & Kunz, C.
Partner: UNT Libraries Government Documents Department

Overtone production of soft x-rays with free-electron lasers

Description: Two one-dimensional free-electron laser codes have recently been written that include harmonic generation. A comparison of the results of these codes show that a self-consistent treatment of the harmonic interaction is not required in the presence of a strong fundamental field. Use of these codes to predict the effects of emittance on harmonic production have been conducted. The effects of wiggler-field amplitude fluctuations and odd-harmonic wiggler-field components on the harmonic-radiation production are also discussed.
Date: January 1, 1986
Creator: Schmitt, M.J.; Elliott, C.J.; Lee, K. & McVey, B.D.
Partner: UNT Libraries Government Documents Department


Description: Last year, the X27A beamline at the National Synchrotron Light Source (NSLS) became dedicated solely to X-Ray Computed Microtomography (XCMT). This is a third-generation instrument capable of producing tomographic volumes of 1-2 micron resolution over a 2-3mm field of view. Recent enhancements will be discussed. These have focused on two issues: the desire for real-time data acquisition and processing and the need for highly monochromatic beam (.1 % energy bandpass). The latter will permit k-edge subtraction studies and will provide improved image contrast from below the Cr (6 keV) up to the Cs (36 keV) k-edge. A range of applications that benefit from these improvements will be discussed as well. These two goals are somewhat counterproductive, however; higher monochromaticity yields a lower flux forcing longer data acquisition times. To balance the two, a more efficient scintillator for X-ray conversion is being developed. Some testing of a prototype scintillator has been performed; preliminary results will be presented here. In the meantime, data reconstruction times have been reduced, and the entire tomographic acquisition, reconstruction and volume rendering process streamlined to make efficient use of synchrotron beam time. A Fast Filtered Back Transform (FFBT) reconstruction program recently developed helped to reduce the time to reconstruct a volume of 150 x 150 x 250 pixels{sup 3} (over 5 million voxels) from the raw camera data to 1.5 minutes on a dual R10,000 CPU. With these improvements, one can now obtain a ''quick look'' of a small tomographic volume ({approximately}10{sup 6}voxels) in just over 15 minutes from the start of data acquisition.
Date: July 23, 1999
Creator: DOWD,B.A.
Partner: UNT Libraries Government Documents Department

Electrical resistivity measurements of a dense aluminum plasma

Description: In this paper the authors report results of experiments to measure the electrical resistivity for a dense strongly coupled aluminum plasma. These plasmas cover the density and temperature range from near solid density and room temperature to .03x solid and 40 eV. These conditions give values of {Lambda} = 5--6. The results indicate the resistivity is higher in this regime than most theories. Only the results of some density functional calculations give results consistent with the data.
Date: September 1, 1995
Creator: Benage, J.F. Jr.; Shanahan, W.R. & Murillo, M.S.
Partner: UNT Libraries Government Documents Department

Target area design issues for implementing direct drive on the National Ignition Facility

Description: NIF will be configured in its baseline design to achieve ignition and gain using the indirect drive approach. However, the requirements require the design to not preclude the conduct of inertial confinement fusion experiments using direct drive. This involves symmetrical illumination of an ICF capsule, where each beam fully subtends the capsule. The re-directing of 24 of the 48 NIF beamlines (2x2 beamlet group each) from 30 and 50{degree} cone angles to 75{degree} cone angles near the chamber `equator` is required. This would be done by adjusting intermediate transport mirrors so that the beams intercept different final mirrors in the Target Bay and be directed into final optics assemblies attached to chamber ports positioned at the new port locations. Space for converting from one irradiation scheme to another is a problem; also NIF user needs cannot be compromised by direct drive needs. Target for direct drive, absent a hohlraum, emits much fewer cold x rays than for indirect drive. Further, the irradiation scheme may not result in the absorption of all the 3{omega} light and this may create a hazard to the NIF chamber first wall. This paper describes possible design features of the NIF Target Area to allow conversion to direct drive and discusses some differences in post-shot conditions created compared to indirect drive.
Date: June 14, 1996
Creator: Tobin, M.; Karpenko, V.; Burnham, A. & Peterson, R.
Partner: UNT Libraries Government Documents Department

Time resolved, 2-D hard X-ray imaging of relativistic electron-beam target interactions on ETA-II

Description: Advanced radiographic applications require a constant source size less than 1 mm. To study the time history of a relativistic electron beam as it interacts with a bremsstrahlung converter, one of the diagnostics they use is a multi-frame time-resolved hard x-ray camera. They are performing experiments on the ETA-II accelerator at Lawrence Livermore National Laboratory to investigate details of the electron beam/converter interactions. The camera they are using contains 6 time-resolved images, each image is a 5 ns frame. By starting each successive frame 10 ns after the previous frame, they create a 6-frame movie from the hard x-rays produced from the interaction of the 50-ns electron beam pulse.
Date: November 1998
Creator: Crist, C. E.; Sampayan, S.; Westenskow, G.; Caporaso, G.; Houck, T.; Weir, J. et al.
Partner: UNT Libraries Government Documents Department

Hard x-ray production from high intensity laser solid interactions

Description: Intense laser (> 10{sup 21} W/cm{sup 2}) driven hard x-ray sources offer a new alternative to conventional electron accelerator bremsstrahlung sources. These laser driven sources offer considerable simplicity in design and cost advantage for multiple axis views and have the potential for much higher spatial and temporal resolution than is achievable with accelerator sources We have begun a series of experiments using the Petawatt Laser system at LLNL to determine the potential of these sources for radiography applications Absolutely calibrated spectra extending to 20 MeV and high resolution radiographs through a {rho}r{>=}150 gm/cm{sup 2} have been obtained The physics of these sources and the scaling relationships and laser technology required to provide the dose levels necessary for radiography applications will be discussed Diagnostics of the laser produced electrons and photons will be addressed
Date: June 3, 1998
Creator: Sefcik, J. A.
Partner: UNT Libraries Government Documents Department