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Ultrashort x-ray backlighters and applications

Description: Previously, using ultrashort laser pulses focused onto solid targets, we have experimentally studied a controllable ultrafast broadband radiation source in the extreme ultraviolet for time-resolved dynamical studies in ultrafast science [J. Workman, A. Maksimchuk, X. Llu, U. Ellenberger, J. S. Coe, C.-Y. Chien, and D. Umstadter, ``Control of Bright Picosecond X-Ray Emission from Intense Sub- Picosecond Laser-Plasma Interactions,`` Phys. Rev. Lett. 75, 2324 (1995)]. Once armed with a bright ultrafast broadband continuum x-ray source and appropriate detectors, we used the source as a backlighter to study a remotely produced plasma. The application of the source to a problem relevant to high-density matter completes the triad: creating and controlling, efficiently detecting, and applying the source. This work represented the first use of an ultrafast laser- produced x-ray source as a time-resolving probe in an application relevant to atomic, plasma and high-energy-density matter physics. Using the x-ray source as a backlighter, we adopted a pump-probe geometry to investigate the dynamic changes in electronic structure of a thin metallic film as it is perturbed by an ultrashort laser pulse. Because the laser deposits its energy in a skin depth of about 100 {Angstrom} before expansion occurs, up to gigabar pressure shock waves lasting picosecond in duration have been predicted to form in these novel plasmas. This raises the possibility of studying high- energy-density matter relevant to inertial confinement fusion (ICF) and astrophysics in small-scale laboratory experiments. In the past, time-resolved measurements of K-edge shifts in plasmas driven by nanosecond pulses have been used to infer conditions in highly compressed materials. In this study, we used 100-fs laser pulses to impulsively drive shocks into a sample (an untamped 1000 {Angstrom} aluminum film on 2000 {Angstrom} of parylene-n), measuring L-edge shifts.
Date: August 1, 1997
Creator: Umstadter, D., University of Michigan
Partner: UNT Libraries Government Documents Department

Rosat-Green bank sample of intermediate BL Lac objects

Description: The Rosat-GreenBank BLLac sample consists of 119 objects and smoothly bridges the gap between the previously disparate subclasses of radio- and X-ray-selected objects. Further study of this sample should provide useful constraints to the unified scheme and help determine if modifications are necessary.
Date: April 1, 1997
Creator: Laurent-Muchleisen, S.A.; Kollgaurd, R.I. & Feigelson, E.D.
Partner: UNT Libraries Government Documents Department

X-Ray Scattering Applications Using Pulsed X-Ray Sources

Description: Pulsed x-ray sources have been used in transient structural phenomena investigations for over fifty years; however, until the advent of synchrotrons sources and the development of table-top picosecond lasers, general access to ligh temporal resolution x-ray diffraction was relatively limited. Advances in diffraction techniques, sample excitation schemes, and detector systems, in addition to IncEased access to pulsed sources, have ld tO what is now a diverse and growing array of pulsed-source measurement applications. A survey of time-resolved investigations using pulsed x-ray sources is presented and research opportunities using both present and planned pulsed x-ray sources are discussed.
Date: May 23, 1999
Creator: Larson, B.C.
Partner: UNT Libraries Government Documents Department

Faraday cup measurements of the plasma plume produced at an x-ray converter

Description: The next generation of radiographic machines based on induction accelerators is expected to generate multiple, small diameter x-ray spots of high intensity. Experiments to study the interaction of the electron beam with the x-ray converter are being performed at the Lawrence Livermore National Laboratory (LLNL) using the 6-MeV, 2-kA Experimental Test Accelerator (ETA) electron beam. The physics issues of greatest concern can be separated into two categories. The multiple pulse issue involves the interaction of subsequent beam pulses with the expanding plasma plume generated by earlier pulses striking the x-ray converter. The plume expands at several millimeters per microsecond and defines the minimum transverse spacing of the pulses. The single pulse issue is more subtle and involves the extraction of light ions by the head of the beam pulse. These light ions might propagate at velocities of several millimeters per nanosecond through the body of the incoming pulse resulting in a moving focus prior to the converter. In this paper we describe Faraday cup measurements performed to quantify the plasma plume expansion and velocities of light ions.
Date: August 17, 1998
Creator: Garcia, M; Houck, T L & Sampayan, S E
Partner: UNT Libraries Government Documents Department


Description: The detector is an x-ray streak camera running in accumulation mode for time resolved x-ray studies at the existing third generation synchrotron facilities and will also be used for the development and applications of the fourth generation x-ray sources. We have made significant progress on both the detector development and its applications at Synchrotron facilities.
Date: June 20, 2005
Creator: Chang, Zenghu
Partner: UNT Libraries Government Documents Department

Decoding sequential vs non-sequential two-photon double ionizationof helium using nuclear recoil

Description: Above 54.4 eV, two-photon double ionization of helium isdominated by a sequential absorption process, producing characteristicbehavior in the single and triple differential cross sections. We showthat the signature of this process is visible in the nuclear recoil crosssection, integrated over all energy sharings of the ejected electrons,even below the threshold for the sequential process. Since nuclear recoilmomentum imaging does not require coincident photoelectron measurement,the predicted images present a viable target for future experiments withnew short-pulse VUV and soft X-ray sources.
Date: January 7, 2008
Creator: Horner, Daniel A.; Rescigno, Thomas N. & McCurdy, C. William
Partner: UNT Libraries Government Documents Department

Compton Scattering X-Ray Sources Driven by Laser Wakefield Acceleration

Description: Recent laser wakefield acceleration experiments have demonstrated the generation of femtosecond, nano-Coulomb, low emittance, nearly monokinetic relativistic electron bunches of sufficient quality to produce bright, tunable, ultrafast x-rays via Compton scattering. Design parameters for a proof-of-concept experiment are presented using a three-dimensional Compton scattering code and a laser-plasma interaction particle-in-cell code modeling the wakefield acceleration process; x-ray fluxes exceeding 10{sup 22} s{sup -1} are predicted, with a peak brightness > 10{sup 20} photons/(mm{sup 2} x mrad{sup 2} x s x 0.1% bandwidth).
Date: October 19, 2005
Creator: Hartemann, F V; Gibson, D J; Brown, W J; Rousse, A; Phuoc, K T & Pukhov, A
Partner: UNT Libraries Government Documents Department

A Novel Compact Pyroelectric X-Ray and Neutron Source

Description: This research was focused on the utilization of pyroelectric crystals for generation of radiation. When in constant temperature pyroelectric crystals are spontaneously polarized. The polarization causes internal charges to accumulate near the crystal faces and masking charges from the environment are attracted to the crystal faces and neutralize the charge. When a pyroelectric crystal is heated or cooled it becomes depolarized and the surface charges become available. If the heating or cooling is done on a crystal in vacuum where no masking charges are available, the crystal becomes a charged capacitor and because of its small capacitance large potential develops across the faces of the crystal.
Date: August 31, 2007
Creator: Danon, Yaron
Partner: UNT Libraries Government Documents Department

Science and Technology Review March 2006

Description: This month's issue has the following articles: (1) Without Fanfare, Technicians Safely Keep the Laboratory Humming--Commentary by Bruce T. Goodwin; (2) These People Make Things Happen--Technicians at Lawrence Livermore, comprising more than 20 percent of the workforce, are essential to research efforts. March 2006; (3) The Shocking Truth about Detonations and Metals--The multichannel x-ray system Hydra records the changes in metals undergoing a high-explosives shock, revealing phenomena not predicted by material models; (4) Floating into Thin Air--High-flying balloon gathers images from x-ray sources that are out of this world; and (5) Carbon Goes Full Cycle in the Amazon--Recent measurements indicate that the Amazon River basin returns carbon to the atmosphere in only 5 years.
Date: January 18, 2006
Creator: Aufderheide, M B
Partner: UNT Libraries Government Documents Department

High Brightness, Laser-Driven X-ray Source for Nanoscale Metrology and Femtosecond Dynamics

Description: This project developed and demonstrated a new, bright, ultrafast x-ray source based upon laser-driven K-alpha generation, which can produce an x-ray flux 10 to 100 times greater than current microfocus x-ray tubes. The short-pulse (sub-picosecond) duration of this x-ray source also makes it ideal for observing time-resolved dynamics of atomic motion in solids and thin films.
Date: February 26, 2007
Creator: Siders, C W; Crane, J K; Semenov, V; Betts, S; Kozioziemski, B; Wharton, K et al.
Partner: UNT Libraries Government Documents Department

High K-alpha X-ray Conversion Efficiency From Extended Source Gas Jet Targets Irradiated by Ultra Short Laser Pulses

Description: The absolute laser conversion efficiency to K{sub {alpha}}-like inner shell x-rays (integrated from K{sub {alpha}} to K{sub {beta}}) is observed to be an order of magnitude higher in argon gas jets than in solid targets due to enhanced emission from higher ionization stages following ultra short pulse laser irradiation. Excluding the higher ionization stages, the conversion efficiency to near-cold K{sub {alpha}} is the same in gas jets as in solid targets. These results demonstrate that gas jet targets are bright, high conversion efficiency, high repetition rate, debris-free multi-keV x-ray sources for spectrally resolved scattering and backlighting of rapidly evolving dense matter.
Date: November 1, 2007
Creator: Kugland, N L; Constantin, C; Collette, A; Dewald, E; Froula, D; Glenzer, S H et al.
Partner: UNT Libraries Government Documents Department

Soft x-ray microscopy - a powerful analytical tool to image magnetism down to fundamental length and times scales

Description: The magnetic properties of low dimensional solid state matter is of the utmost interest both scientifically as well as technologically. In addition to the charge of the electron which is the base for current electronics, by taking into account the spin degree of freedom in future spintronics applications open a new avenue. Progress towards a better physical understanding of the mechanism and principles involved as well as potential applications of nanomagnetic devices can only be achieved with advanced analytical tools. Soft X-ray microscopy providing a spatial resolution towards 10nm, a time resolution currently in the sub-ns regime and inherent elemental sensitivity is a very promising technique for that. This article reviews the recent achievements of magnetic soft X-ray microscopy by selected examples of spin torque phenomena, stochastical behavior on the nanoscale and spin dynamics in magnetic nanopatterns. The future potential with regard to addressing fundamental magnetic length and time scales, e.g. imaging fsec spin dynamics at upcoming X-ray sources is pointed out.
Date: August 1, 2008
Creator: Fischer, Peter
Partner: UNT Libraries Government Documents Department

Development of a Novel Tunable X-Ray Source for the RPI-LINAC

Description: This document summarizes the results of a three year effort to develop a parametric x-ray (PXR) source. The emphasis of this research was to demonstrate production of high yield monoenergetic x-rays. Production of PXR is accomplished by placing a crystal in a relativistic electron beam. The process was first demonstrated in 1985 in Russia. Numerous papers were written about the characteristics of PXR from both experimental and theoretical perspectives. The advantage of PXR over other monoenergetic x-ray sources is that it is produced at large angle relative to the electron beam and at high intensity. None of the previous work described in the literature capitalized on this effect to study what is required in order to generate an effective monoenergetic x-ray source that can be used for practical applications. The work summarized here describes the process done in order to optimize the PXR production process by selecting an appropriate crystal and the optimal conditions. The research focused on production of 18 keV x-rays which are suitable for mammography however the results are not limited to this application or energy range. We are the first group to demonstrate x-ray imaging using PXR. Such sources can improve current medical imaging modalities. More research is required in order to design a prototype of a compact source.
Date: November 30, 2004
Creator: Danon, Y. & Block, R. C.
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

Development of a Dynamic Spot Size Diagnostic for Flash Radiographic X-Ray Sources

Description: There has been considerable work in recent years in the development of high-brightness, high-dose flash x-ray radiographic sources. Spot size is one of several parameters that helps characterize source performance and provides a figure of merit to assess the suitability of various sources to specific experimental requirements. Time-integrated spot-size measurements using radiographic film and a high-Z rolled-edge object have been used for several years with great success. The Advanced Radiographic Technologies program thrust to improve diode performance requires extending both modeling and experimental measurements into the transient time domain. A new Time Resolved Spot Detector (TRSD) is under development to provide this information. In this paper we report the initial results of the performance of a 148-element scintillating fiber array that is fiber-optically coupled to a gated streak camera. Spatial and temporal resolution results are discussed and the data obtained from the Sand ia National Laboratories (SNL) RITS-3 (Radiographic Integrated Test Stand) accelerator are presented.
Date: June 1, 2003
Creator: Droemer, D. W.; Lutz, S.; Devore, D.; Rovang, D.; Portillo, S. & Maenchen, J.
Partner: UNT Libraries Government Documents Department

Compton scattering in the ALS booster

Description: Femtosecond x-ray pulses may be generated by 90{degrees} Compton side scattering of a short visible laser beam by a well-focused relativistic electron beam. A proof-of-principle experiment is underway using the ALS linac. From this experiment an x-ray pulse of 10{sup 5} photons with a duration of 230 fs in a bandwidth of 10% at 10 Hz is expected. In this paper we explore using the ALS booster instead to increase the average x-ray flux. To generate the small beam size we plan to radiation damp electrons by accelerating them to 600 MeV and decelerate quickly to 50 MeV before intra-beam scattering can increase the beam size. We can achieve a vertical emittance of <5 {times} 10{sup {minus}9} m-rad. With a small modification of the booster lattice it is possible to focus the beam to a vertical beta function of {Beta}{sub y}* = 10 cm. By reflecting the incident laser pulse many times we expect to be able to obtain an increase of the average x-ray flux.
Date: April 1, 1995
Creator: Robin, D.; Kim, C. & Sessler, A.
Partner: UNT Libraries Government Documents Department

Cryogenic xenon droplets for advanced lithography

Description: A cryogenic xenon droplet production system for use in anadvanced laser plasma source for x-ray lithography has been designed, fabricated, and tested at ORNL. The droplet generator is based on proven (ink jet printer) drop-on-demand.
Date: April 1, 1996
Creator: Gouge, M.J. & Fisher, P.W.
Partner: UNT Libraries Government Documents Department

Insertion devices at the advanced photon source

Description: The insertion devices being installed at the Advanced Photon Source cause the stored particle beam to wiggle, emitting x-rays with each wiggle. These x-rays combine to make an intense beam of radiation. Both wiggler and undulator types of insertion devices are being installed; the characteristics of the radiation produced by these two types of insertion devices are discussed, along with the reasons for those characteristics.
Date: July 1, 1996
Creator: Moog, E.R.
Partner: UNT Libraries Government Documents Department

Higher order parametric x-ray spectra in mosaic graphite and single silicon crystals

Description: We have observed up to eight orders (n) in the spectra of parametric x-radiation, in the range 5-40 keV, produced by interaction of a 90-MeV electron beam with mosaic graphite and 90 and 35 MeV beams with single Si crystals, Measured yields and intensity ratios, I(n{ge}2)/I(n=1), in graphite are not in agreement with PXR theory for mosaic crystals. In comparison, yield and ratios of intensities in Si are close to preductions for perfect crystals. Bandwidths of spectral lines measured in both Si and graphite are in good agreement with theory and are determined by the angular field of view of the detector.
Date: December 31, 1993
Creator: Fiorito, R.B.; Rule, D.W. & Maruyama, X.K.
Partner: UNT Libraries Government Documents Department