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Structural studies of intercalants

Description: The structure of stage 2 potassium intercalated graphite, KC/sub 24/, is discussed in both the ordered and disordered phases. A one-dimensional model is used to illustrate the qualitative features of the KC/sub 24/ diffraction patterns.
Date: January 1, 1981
Creator: Hastings, J.B.
Partner: UNT Libraries Government Documents Department

X-ray monochromator geometry for focusing synchrotron radiation above 10 keV

Description: The relative merits of crystals versus mirrors for focusing synchrotron radiation at energies above 10 keV are explored. As mirrors have critical angles of reflection typically 1/20 of the Bragg scattering angles for crystals, large mirror surface areas are required. Sagittal focusing is weak for mirrors and limits the amount of radiation intercepted. Crystals bent to a simple cylindrical curvature are shown to accept large divergences of radiation for sagittal focusing. At a magnification near 1/3, the cylindrically curved crystals are shown to make the proper Bragg angle for energies above 5 keV and for divergences larger than 10 mrad and to produce x-ray beams which are approximately focused.
Date: January 1, 1979
Creator: Sparks, C.J. Jr.; Borie, B.S. & Hastings, J.B.
Partner: UNT Libraries Government Documents Department

A new apparatus for the study of nuclear Bragg scattering

Description: A new monochromator system has been constructed which provides an energy resolution of 0.005 eV and an angular divergence of 0.4 arc seconds at an energy of 14.413 keV. In conjunction with a highly perfect crystal of isotopically enriched /sup 57/Fe/sub 2/O/sub 3/, a beam of nuclear resonant photons was extracted from the synchrotron continuum with signal to noise ratio of 100:1, and an intensity of >2 quanta/sec. 14 refs., 9 figs.
Date: January 1, 1987
Creator: Siddons, D.P.; Hastings, J.B. & Faigel, G.
Partner: UNT Libraries Government Documents Department

X-ray Free-electron Lasers

Description: In a free-electron laser (FEL) the lasing medium is a high-energy beam of electrons flying with relativistic speed through a periodic magnetic field. The interaction between the synchrotron radiation that is produced and the electrons in the beam induces a periodic bunching of the electrons, greatly increasing the intensity of radiation produced at a particular wavelength. Depending only on a phase match between the electron energy and the magnetic period, the wavelength of the FEL radiation can be continuously tuned within a wide spectral range. The FEL concept can be adapted to produce radiation wavelengths from millimeters to Angstroms, and can in principle produce hard x-ray beams with unprecedented peak brightness, exceeding that of the brightest synchrotron source by ten orders of magnitude or more. This paper focuses on short-wavelength FELs. It reviews the physics and characteristic properties of single-pass FELs, as well as current technical developments aiming for fully coherent x-ray radiation pulses with pulse durations in the 100 fs to 100 as range. First experimental results at wavelengths around 100 nm and examples of scientific applications planned on the new, emerging x-ray FEL facilities are presented.
Date: February 23, 2007
Creator: Feldhaus, J.; /DESY; Arthur, J.; Hastings, J.B. & /SLAC
Partner: UNT Libraries Government Documents Department

National synchrotron light source. Activity report, October 1, 1995--September 30, 1996

Description: The hard work done by the synchrotron radiation community, in collaboration with all those using large-scale central facilities during 1995, paid off in FY 1996 through the DOE`s Presidential Scientific Facilities Initiative. In comparison with the other DOE synchrotron radiation facilities, the National Synchrotron Light Source benefited least in operating budgets because it was unable to increase running time beyond 100%-nevertheless, the number of station hours was maintained. The major thrust at Brookhaven came from a 15% increase in budget which allowed the recruitment of seven staff in the beamlines support group and permitted a step increment in the funding of the extremely long list of upgrades; both to the sources and to the beamlines. During the December 1995 shutdown, the VUV Ring quadrant around U10-U12 was totally reconstructed. New front ends, enabling apertures up to 90 mrad on U10 and U12, were installed. During the year new PRTs were in formation for the infrared beamlines, encouraged by the investment the lab was able to commit from the initiative funds and by awards from the Scientific Facilities Initiative. A new PRT, specifically for small and wide angle x-ray scattering from polymers, will start work on X27C in FY 1997 and existing PRTs on X26C and X9B working on macromolecular crystallography will be joined by new members. Plans to replace aging radio frequency cavities by an improved design, originally a painfully slow six or eight year project, were brought forward so that the first pair of cavities (half of the project for the X-Ray Ring) will now be installed in FY 1997. Current upgrades to 350 mA initially and to 438 mA later in the X-Ray Ring were set aside due to lack of funds for the necessary thermally robust beryllium windows. The Scientific Facilities Initiative allowed purchase of all 34 ...
Date: May 1, 1997
Creator: Rothman, E.Z. & Hastings, J.B.
Partner: UNT Libraries Government Documents Department

In vacuum undulator task force report

Description: Historically the NSLS has been active in R&D for state-of-the-art electron beams, photon beams and x-ray optics. One of the available straight sections has therefore been dedicated to insertion device R&D. Over the past five to seven years a program aimed at exploiting the very small vertical {beta} function in the straight sections has yielded first a prototype small gap undulator (PSGU) and then an in-vacuum undulator (IVUN). The IVUN sources attain a brightness similar to the existing hybrid wigglers in X21 and X25. They radiate significantly lower total power than the wigglers but produce higher power densities. They provide undulator rather than wiggler spectra. Because of the small gaps and small periods there is not much tunability in these devices and they will have to be purpose-built for a specific scientific program. The original IVUN parameters were chosen for in-elastic x-ray scattering, similar to the scientific program on X21. This put the fundamental at 4.6 keV and the third harmonic at 13.8 keV. The question that this new possible insertion device poses is what science programs can best take advantage of this new insertion device source? To answer this, a task force was formed by M. Hart, NSLS Department Chair and charged with identifying viable scientific programs that could seek outside funding to construct IVUN beamlines. The task force concentrated on experimental programs that are presently being pursued on new insertion devices worldwide. For example, x-ray photon correlation spectroscopy, which takes advantage of the large coherent flux from undulator sources, was considered. However, this program was not considered as the highest priority. The general area of protein crystallography, however, is ideal for the IVUN source. The unique electron beam optics that makes the IVUN possible in the first place also makes the IVUN ideal as a source for microdiffraction.
Date: June 1, 1998
Creator: Hastings, J.B.; Kao, C.C. & Stefan, P.
Partner: UNT Libraries Government Documents Department

Recent advances in soft x-ray scattering instrumentation at the national synchrotron light source

Description: For the study of condensed matter systems x-ray scattering experiments are often the best choice as they have several desirable features including complete conservation of momentum in the incident and detected particles, well characterized initial and final electronic states, and insensitivity of photon transport to external electric and magnetic fields (as compared to photoelectrons for example). To extend these techniques to the soft x-ray region ({Dirac h}v < 1keV) the lack of suitable detectors, and the difficulties associated with performing scattering experiments in vacuum must be overcome. In this paper we provide details of our instrumental development program, and show some representative examples of experiments we have performed to date. 7 refs., 4 figs.
Date: January 1, 1991
Creator: Johnson, E.D.; Kao, Chi-Chang & Hastings, J.B.
Partner: UNT Libraries Government Documents Department

Optical design and performance of the X25 hybrid wiggler beam line at the NSLS

Description: The X25 beam line at the National Synchrotron Light Source (NSLS) began full-power commissioning in 1990. It extracts radiation from a 27 pole hybrid wiggler, which produces up to 1.8 kW of total power with a peak horizontal density of 450 W/mrad and critical energy of 4.6 keV. The design and performance of the beam line optics are described, in particular the cooling of the first monochromator crystal. 28 refs., 5 figs.
Date: January 1, 1991
Creator: Berman, L.E.; Hastings, J.B.; Oversluizen, T. & Woodle, M.
Partner: UNT Libraries Government Documents Department

Surface extended x-ray absorption fine structure of low-Z absorbates using fluorescence detection

Description: Comparison of x-ray fluorescence yield (FY) and electron yield surface extended x-ray absorption fine structure spectra above the S K-edge for c(2 x 2) S on Ni(100) reveals an order of magnitude higher sensitivity of the FY technique. Using FY detection, thiophene (C/sub 4/H/sub 4/S) chemisorption on Ni(100) is studied with S coverages down to 0.08 monolayer. The molecule dissociates at temperatures as low as 100K by interaction with fourfold hollow Ni sites. Blocking of these sites by oxygen leaves the molecule intact.
Date: May 1, 1985
Creator: Stoehr, J.; Kollin, E.B.; Fischer, D.A.; Hastings, J.B.; Zaera, F. & Sette, F.
Partner: UNT Libraries Government Documents Department

Suppression of charge scattering in Moessbauer experiments using synchrotron radiation

Description: The extremely small ratio of linewidth to energy combined with the character of recoil free absorption and reemission makes the low lying nuclear resonances a unique spectroscopic tool. Further, considering the simplicity of performing Moessbauer experiments, they have become very useful in a wide range of disciplines. [sup 57]Fe has remained the most widely used isotope despite its low natural abundance (2%) because iron is ubiquitous in nature and shows a strong effect. The energy width of this resonance corresponds to a lifetime of 140 nsec of the excited state. Therefore in principle time differential spectroscopy is possible. Using the time differential measurement one is no longer restricted to a nuclear source, in fact a short pulse excitation is favored in such experiments. The concept of using a pulsed source and time gating to isolate the resonant scattering was already suggested in 1962. In 1974 it was noted that synchrotron radiation (SR) was ideally suited to this task. Although the time gating technique is conceptually simple the bandwidth of SR poses significant technical difficulties. In this paper we will discuss the extraction of the nuclear signal from the overwhelming background, which is the central problem in SR-based Moessbauer experiments. We will only, consider the [sup 57]Fe-isotope, although other isotopes might be of interest in a SR-based experiment. Although SR sources have the disadvantages of creating this high background and being limited in beam-time and location, new and unique opportunities make them very attractive even with these difficulties. For this reason research and development groups at every major SR facility worldwide are increasingly working on Moessbauer experiments, stimulated by the first successful observation of nuclear Bragg scattering (NBS) using SR in 1984.
Date: January 1, 1992
Creator: Bergmann, U.; Siddons, D.P. & Hastings, J.B.
Partner: UNT Libraries Government Documents Department

Resonant and non-resonant magnetic scattering

Description: The tunability and the polarization of synchrotron radiation open upon new possibilities for the study of magnetism. Studies on magnetic materials performed at the National Synchrotron Light Source are reviewed, and thy fall into four areas: structure, evolution of magnetic order, separation of L and S, and resonance effects. In the vicinity of atomic absorption edges, the Faraday effect, magnetic circular dichroism, and resonant magnetic scattering are all related resonance effects which measure the spin polarized density of states. The production and analysis of polarized beams are discussed in the context of the study of magnetism with synchrotron radiation.
Date: January 1, 1991
Creator: McWhan, D.B.; Hastings, J.B.; Kao, C.C. & Siddons, D.P.
Partner: UNT Libraries Government Documents Department

Report from the NSLS workshop: Sources and applications of high intensity uv-vuv light

Description: A workshop was held to evaluate sources and applications of high intensity, ultra violet (UV) radiation for biological, chemical, and materials sciences. The proposed sources are a UV free electron laser (FEL) driven by a high brightness linac and undulators in long, straight sections of a specially designed low energy (400 MeV) storage ring. These two distinct types of sources will provide a broad range of scientific opportunities that were discussed in detail during the workshop.
Date: January 1, 1990
Creator: Johnson, E.D. & Hastings, J.B. (eds.)
Partner: UNT Libraries Government Documents Department

Initial Search for 9-keV XTR from a 28-GeV Beam at SPPS

Description: The potential to use x-ray transition radiation (XTR) as a beam diagnostic and coherent XTR (CXTR) as a gain diagnostic in an x-ray FEL was proposed previously. At that time we noted that the unique configuration of the SLAC Sub-picosecond Photon Source (SPPS) with its known x-ray wiggler source, a special three-element x-ray monochromator, x-ray transport line, and experimental end station with x-ray detectors made it an ideal location for an XTR feasibility experiment. Estimates of the XTR compared to the SPPS source strength were done, and initial experiments were performed in September 2005. Complementary measurements on optical transition radiation (OTR) far-field images from a 7-GeV beam are also discussed.
Date: April 16, 2007
Creator: Lumpkin, A.H.; /Argonne; Hastings, J.B.; /SLAC; Rule, D.W. & Ctr., /Naval Surface Warfare
Partner: UNT Libraries Government Documents Department

Inelastic x-ray scattering at the National Synchrotron Light

Description: The research program at the inelastic x-ray scattering beamline at the National Synchrotron Light Source is focused on the study of elementary excitations in condensed matter with total energy resolution on the order of 0.1 eV to 1.0 eV. Results from selected experiments are reported to demonstrate the capability of the beamline as well as the information can be obtained from inelastic x- ray scattering experiments.
Date: December 31, 1995
Creator: Kao, C.-C.; Caliebe, W.A.; Hastings, J.B.; Hamalainen, K. & Krisch, M.H.
Partner: UNT Libraries Government Documents Department

Application of synchrotron radiation to elemental analysis

Description: The use of a synchrotron storage ring as a high brightness source for production of monoergic, variable energy, and highly polarized x-ray beams promises to revolutionize the field of elemental analysis. The results of exploratory work using the Cornell synchrotron facility, CHESS, will be described. Design considerations and features of the new X-Ray Microprobe Facility now under construction at the Brookhaven National Synchrotron Light Source will be presented. This facility will be used for bulk analysis and for microanalysis with an initial spatial resolution of the order of 30 ..mu..m.
Date: January 1, 1983
Creator: Jones, K.W.; Gordon, B.M.; Hanson, A.L.; Hastings, J.B.; Howells, M.R.; Kraner, H.W. et al.
Partner: UNT Libraries Government Documents Department

BNL Activities in Advanced Neutron Source Development: Past and Present

Description: Brookhaven National Laboratory has been involved in advanced neutron sources almost from its inception in 1947. These efforts have mainly focused on steady state reactors beginning with the construction of the first research reactor for neutron beams, the Brookhaven Graphite Research Reactor. This was followed by the High Flux Beam Reactor that has served as the design standard for all the subsequent high flux reactors constructed worldwide. In parallel with the reactor developments BNL has focused on the construction and use of high energy proton accelerators. The first machine to operate over 1 GeV in the world was the Cosmotron. The machine that followed this, the AGS, is still operating and is the highest intensity proton machine in the world and has nucleated an international collaboration investigating liquid metal targets for next generation pulsed spallation sources. Early work using the Cosmotron focused on spallation product studies for both light and heavy elements into the several GeV proton energy region. These original studies are still important today. In this report we discuss the facilities and activities at BNL focused on advanced neutron sources. BNL is involved in the proton source for the Spallation Neutron source, spectrometer development at LANSCE, target studies using the AGS and state-of-the-art neutron detector development.
Date: June 14, 1998
Creator: Hastings, J.B.; Ludewig, H.; Montanez, P.; Todosow, M.; Smith, G.C. & Larese, J.Z.
Partner: UNT Libraries Government Documents Department

BNL ACTIVITIES IN ADVANCED NEUTRON SOURCE DEVELOPMENT: PAST AND PRESENT

Description: Brookhaven National Laboratory has been involved in advanced neutron sources almost from its inception in 1947. These efforts have mainly focused on steady state reactors beginning with the construction of the first research reactor for neutron beams, the Brookhaven Graphite Research Reactor. This was followed by the High Flux Beam Reactor that has served as the design standard for all the subsequent high flux reactors constructed worldwide. In parallel with the reactor developments BNL has focused on the construction and use of high energy proton accelerators. The first machine to operate over 1 GeV in the world was the Cosmotron. The machine that followed this, the AGS, is still operating and is the highest intensity proton machine in the world and has nucleated an international collaboration investigating liquid metal targets for next generation pulsed spallation sources. Early work using the Cosmotron focused on spallation product studies for both light and heavy elements into the several GeV proton energy region. These original studies are still important today. In the sections below the authors discuss the facilities and activities at BNL focused on advanced neutron sources. BNL is involved in the proton source for the Spallation Neutron source, spectrometer development at LANSCE, target studies using the AGS and state-of-the-art neutron detector development.
Date: June 14, 1998
Creator: HASTINGS,J.B.; LUDEWIG,H.; MONTANEZ,P.; TODOSOW,M.; SMITH,G.C. & LARESE,J.Z.
Partner: UNT Libraries Government Documents Department

Nuclear Bragg x-ray scattering of synchrotron radiation by sup 57 Fe sub 2 O sub 3

Description: A program of studies of nuclear Bragg x-ray scattering with {sup 57}Fe{sub 2}O{sub 3} at the National Synchrotron Light Source at Brookhaven National Laboratory and at the Cornell University CHESS facility is reviewed. Two main areas, instrumentation development and studies of dynamical diffraction processes, are described. The latter area has included: measurements of the temporal behaviour of nuclear collective decay mode and direct observation of polarization mixing. 7 refs., 5 figs.
Date: January 1, 1989
Creator: Haustein, P.E.; Berman, L.E.; Faigel, G.; Grover, J.R.; Hastings, J.B. & Siddons, D.P.
Partner: UNT Libraries Government Documents Department

A high resolution x-ray fluorescence spectrometer for near edge absorption studies

Description: A high resolution fluorescence spectrometer using a Johann geometry in a back scattering arrangement was developed. The spectrometer, with a resolution of 0.3 eV at 6.5 keV, combined with an incident beam, with a resolution of 0.7 eV, form the basis of a high resolution instrument for measuring x-ray absorption spectra. The advantages of the instrument are illustrated with the near edge absorption spectrum of dysprosium nitrate. 10 refs., 4 figs.
Date: January 1, 1991
Creator: Stojanoff, V.; Hamalainen, K.; Siddons, D.P.; Hastings, J.B.; Berman, L.E.; Cramer, S. et al.
Partner: UNT Libraries Government Documents Department

Ultrafast Time-Resolved Electron Diffraction with Megavolt Electron Beams

Description: An rf photocathode electron gun is used as an electron source for ultrafast time-resolved pump-probe electron diffraction. We observed single-shot diffraction patterns from a 160 nm Al foil using the 5.4 MeV electron beam from the Gun Test Facility at the Stanford Linear Accelerator. Excellent agreement with simulations suggests that single-shot diffraction experiments with a time resolution approaching 100 fs are possible.
Date: October 24, 2006
Creator: Hastings, J.B.; /SLAC; Rudakov, F.M.; U., /Brown; Dowell, D.H.; Schmerge, J.F. et al.
Partner: UNT Libraries Government Documents Department

Precision Measurement of the Undulator K Parameter using Spontaneous Radiation

Description: Obtaining precise values of the undulator parameter, K, is critical for producing high-gain FEL radiation. At the LCLS [1], where the FEL wavelength reaches down to 1.5 {angstrom}, the relative precision of K must satisfy ({Delta}K/K){sub rms} {approx}&lt; 0.015% over the full length of the undulator. Transverse misalignments, construction errors, radiation damage, and temperature variations all contribute to errors in the mean K values among the undulator segments. It is therefore important to develop some means to measure relative K values, after installation and alignment. We propose a method using the angle-integrated spontaneous radiation spectrum of two nearby undulator segments, and the natural shot-to-shot energy jitter of the electron beam. Simulation of this scheme is presented using both ideal and measured undulator fields. By ''leap-frogging'' to different pairs of segments with extended separations we hope to confirm or correct the values of K, including proper tapering, over the entire 130-m long LCLS undulator.
Date: April 17, 2007
Creator: Welch, J.J.; Arthur, J.; Emma, P.; Hastings, J.B.; Huang, Z.; Nuhn, H.D. et al.
Partner: UNT Libraries Government Documents Department