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X-RAY RUNS: Apply for Beamtime

2017  March 15 - April 24

2017  May 17 - June 29
2017  BTR deadline: 04/17/17

2017  October 11 - December 21
2017  Proposal deadline: 08/01/17
2017  BTR deadline: 09/10/17

January 5 - Kenneth Evans-Lutterodt - NSLS     NOTE: Day and Time
January 21 - Sarvjit Shastri - Argonne National Lab
January 24 - Steve Wang - Advanced Photon Source      NOTE: Day
January 28 - Lee Makowski - Northeastern

February 4 - Eric Dufresne - APS
February 14 - Bruce Carlston, LANL          NOTE: Day and Time
February 18 - Vadim Dudnikov, Muons, Inc.
February 25 - Frank Marhauser - Jefferson Lab         CANCELLED

March 2 - Robert Fischetti - ANL           NOTE: Day
March 11 - John Spence - Arizona State University
March 18 - Jonathan Wurtele, University of California at Berkeley
March 25 - Fabio Casagrande, ORNL

April 1 - Peter Leban, Instrumentation Technology          NOTE: Time
April 1 - Qun Liu, BNL
April 8 - Tsun-Kong (T.K.) Sham, University of Western Ontario    NOTE: Location
April 8 - Marit Klein, Karlsruhe Institute of Technology          NOTE: Time
April 22 - Alexei Soares, BNL

May 6 - Edward Snell, Hauptman-Woodward
May 13 - Steven W. Van Sciver, Florida State University

June 17 - Joe Ozelis, Fermilab

July 8 - Dan Abell, Tech X Corporation

Aug 5 - Manuel Sanchez del Rio, ESRF
Aug 12 - CHESS Summer REU Student Presentations

Sept 13 - Robert Roser, Fermi National Laboratory

Oct 7 - Ivan Bazarov, Cornell University
Oct 11 - Ralf Eichhorn, Darmstad University of Technology

Nov 18 - Charles Reece, Jefferson Laboratory

Dec 9 - Russell Mammei, Jefferson Lab

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Friday, December 9, 2011

Russell Mammei
Jefferson Lab

 

"Performance of a Bialkali Photocathode Inside the JLab DC High Voltage Inverted Gun"

Abstract:  Two photocathodes are frequently considered for generating high average current electron beams and/or beams with high brightness: GaAs:Cs and K_2CsSb. Each photocathode has advantages and disadvantages, although some attributes are based on assumptions and not demonstrated performance at “production” accelerator facilities.

To make a well-informed choice for new accelerators applications, the performance of both photocathodes should be measured under identical conditions. To this end Brookhaven National Lab (BNL) and Jefferson Lab (JLab) groups have been collaborating to study the characteristics of K_2CsSb photocathodes in the same DC field that has been used to study GaAs:Cs. In March of 2011, a K_2CsSb photocathode was grown at BNL and successfully transported in vacuum to the Injector Test Stand electron gun at JLab where charge lifetime was evaluated with 440 and 532 nm wavelengths at 100 and 200 kV gun bias voltages while generating dc currents ranging from 1-20 mA. In total ~5000 C of charge has been extracted during these measurements. After beam evaluation, the photocathode was also studied with an SEM/EDS system. An introduction to the Injector Test Stand facility along with the charge lifetime/SEM results will be presented.

 

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Friday, November 18, 2011

Charles Reece, Senior Staff Scientist
Institute for SRF Science & Technology, Jefferson Laboratory

 

"Understanding, Improving, and Exploiting Electropolishing Techniques for Nb SRF Cavities"

Abstract:  Optimum performance of superconducting RF cavities requires care for and control of the surface. SRF is inherently a surface phenomenon, with only the top ~100 nm presenting any influence on the resonant RF fields. As long as extrinsic factors are adequately controlled, e.g. particulate contamination, the effective surface impedance and supportable field amplitude is determined by the composition and topography of this surface layer. Surface topography, even on the micron scale can easily produce local field enhancements that induce losses earlier than expected considering only the mean surface field. If contamination is avoided, the superheating field, the maximum supportable magnetic field, for niobium at ~2K is near 180 mT. A very practical challenge is how to realize surface conditions which approach this level with confident reliability over large surfaces of perhaps complex geometry. To obtain a crystallographically clean and undamaged bulk niobium surface requires chemical removal of material affected during cavity fabrication. For decades the standard means has been chemical etching with a mixture of nitric, hydrofluoric, and phosphoric acids. This yields a clean surface, but not necessarily smooth. Different niobium crystal planes present varying chemical potential and thus reaction rates. Also, residual localized stresses can enhance the local reaction rate, yielding pits where none were before. Electropolishing of niobium, however, is intended to remove surface material in a way that is blind to such local variations, yet more reactive with protrusions than intrusions, both of which contribute to surface leveling. Although application of electropolishing to niobium is not new, only recently has a mechanistic understanding emerged which can be exploited by deliberate process design. The next steps in process development for bulk niobium cavities are toward streamlined protocols and minimized use of hazardous materials. I will review the recent advances in understanding standard electropolishing of niobium and discuss routes for exploiting this understanding toward economical and reliable peak performance from SRF accelerating structures.

 

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NOTE: Day

Tuesday, October 11, 2011

 

Dr. Ralf Eichhorn, Physics Department
Darmstad University of Technology

 

 "SDALINAC, a Recirculating SRF Linac for Nuclear Physics in a University Environment"

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Friday, October 7, 2011

Ivan Bazarov, Assistant Professor of Physics
Cornell University

Presentation:  pptx  (login required)

"Representation of Synchrotron Radiation in Phase Space"

Abstract:  The notion of brightness is most efficiently conveyed by representing rays in phase space (transverse position and momentum). Most physicists are familiar with geometric optics version of such a representation. Wigner has introduced his famous distribution in quantum mechanics to describe a quantum particle in phase space. Naturally, the same distribution can be used to represent light including all the wave phenomena. It provides a natural framework for light propagation and optics matching by transferring the familiar 'baggage' of accelerator physics (beta function, emittance, phase space transforms, etc.) to synchrotron radiation. I will show how this distribution can be a practical tool to describe (partially) coherent sources of synchrotron radiation such as Energy Recovery Linac.

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***NOTE DAY / PLACE / TIME***

Tuesday, June 17, 2011
2:30PM
120 Physical Sciences Building

Robert Roser,
Fermi National Laboratory

 

"Things that go Bump!  The Latest Exciting Results from the Tevatron"

Abstract:  Answers to pressing questions in high energy physics may lie in electroweak symmetry breaking, the phenomenon for explaining why the weak and electromagnetic forces are different. From solving the mystery of dark energy to string theory, our entire philosophy depends on the unknown physics at the electroweak scale. Fermilab’s Tevatron has held the distinction of being at the Energy Frontier for the last decade, operating virtually non-stop and giving physicists enormous data sets. I will present the most recent findings and put them in the context of physics at the electroweak scale.

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Friday, August 12, 2011

CHESS Summer REU Student Presentations

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Friday, August 5, 2011

Presentation:  ppt / pdf

Manuel Sánchez del Río
European Synchrotron Radiation Facility

 "X-ray Optics Simulations and Modeling Software for the ESRF Upgrade Program"

Abstract:  The challenging ESRF Upgrade Programme foresees the reconstruction of about one third of the beamlines. The new beamlines will be very long (more than 100 m) to use routinely micro- and nano-beams. This requires a very high demagnification of the ESRF source, which makes beamline optics design a fundamental concept for the future availability of bright and small beam. At present, during the concept phase, an intense use of computer tools for x-ray optics is necessary, in particular ray-tracing, which has demonstrated to be the most reliable tool for designing and optimizing synchrotron beamlines.

A substantial effort has already been invested at the ESRF in developing optics tools and facilitating their use. I will summarize our existing tools, based on XOP and SHADOW. Some examples of recent simulations will be presented, including all kind of synchrotron optics (reflective, refractive and diffractive). SHADOW3, a new version of the ray-tracing tool is presented. An ambitious project for a worldwide collaboration on the upgrade and development of the existing software and development of new tools is been launched.

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NOTE: Refreshments will not be served

Friday, July 8, 2011

Dan T. Abell
Tech X Corporation

 "Computation of Maps for Realistic and Model RF Cavities"

Abstract:  Imagine a virtual cylinder passing through an rf cavity. Given field data on the surface of that cylinder, one can compute an accurate high-order transfer map for particles traversing the cavity. The technique described in this talk is robust against errors or noise present in the surface data; moreover, it is not limited to accelerating modes. In addition, the technique lends itself to the construction of realistic models, including fringes, of various standing-wave modes. This talk also describes possibilities for computing transfer maps for superposed cavity modes.

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Friday, June 17, 2011

Presentation:  ppt / pdf

Joe Ozelis,
Fermilab

 

"SRF Cavity Vertical Test Infrastructure at Fermilab, and Highlights of the ILC Cavity R&D Program"

Abstract:  Shortly after the decision to pursue a SRF based linear-collider was made, Fermilab began embarking upon a substantial program of developing the required infrastructure and expertise to allow them to become a significant contributor and participant in the field of SRF technology.

One of the crucial facilities identified was for the vertical test of SRF cavities (primarily for what then became known as the ILC). The requirements, specifications, design, and construction of such a facility, along with operational aspects, and planned upgrades/expansion will be discussed. Highlights of various ILC cavity R&D efforts for which this facility has been a critical asset will also be described.

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Friday, May 13, 2011

Presentation:  ppt / pdf

 

Steven W. Van Sciver, Prof. of Engineering
Florida State University

 

"Superfluid Helium from the Macroscopic to the Microscopic"

Abstract:  Superfluid helium (He II) first discovered in the 1930s continues to provide scientists with a fascinating physical system rich with phenomena that challenge experimental and theoretical investigators. Moreover, much of the recent interest in He II has emanated from the wide range of technical applications for the fluid. The combination of anomalous heat transport, low viscosity and low temperature make He II an ideal medium for cooling superconducting magnets and particle accelerators. In turn, these applications have inspired new basic investigations of the fluid dynamic behavior of He II. The presentation will begin with an overview of some of the applications using He II cooling at the National High Magnetic Field Laboratory. With the audience sufficiently motivated, we will then turn to recent research on the transport properties of He II culminating in microscale investigations that may provide new insight into the basic physics of this unique fluid.

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Friday, May 6, 2011

 

Edward Snell, Senior Research Scientist
Hauptman-Woodward Medical Research Institute

 

 

 

"The Application of SAXS, Crystallography and Computational Modeling to a Eukaryotic tRNA Synthetase"

Abstract:  Gln4 is a yeast glutaminyl tRNA synthetase that covalently couples glutamine to the 2'-OH of tRNAGln for its essential role in translation of decoding glutamine codons in mRNA and adding glutamine residues to the growing peptide chain during protein synthesis. Many eukaryotic tRNA synthetases like Gln4 differ from their prokaryotic homologs by the attachment of an additional domain appended to their N or C-terminus, but it is unknown how these domains contribute to tRNA synthetase function, and why they are not found in prokaryotes. Using a combination of SAXS, X-ray crystallography and modeling we have determined the complete structure of Gln4 gaining valuable insight into one of these structurally uncharacterized N-terminal domains. In this talk, the results and methods used will be described.

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Friday, April 22, 2011

Presentation:  pdf

 

Alexei Soares
Brookhaven National Laboratory

 

"Touchless Serial Micro-crystallography using Acoustically Mounted Crystals"

Abstract:  We demonstrate a general strategy to determine structures from showers of microcrystals. It uses acoustic droplet ejection (ADE) to transfer 2.5 nanoliter droplets from the surface of microcrystal slurries, through the air, and onto mounting micromesh pins. Individual microcrystals are located by raster-scanning a several micron X-ray beam across the cryocooled micromeshes. X-ray diffraction datasets merged from several micron-sized crystals are used to solve 1.8 Ǻ resolution crystal structures.

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NOTE: Time and Location

Friday, April 8, 2011
TIME:  12:30PM
Location: 120 Physical Sciences Building

 

Tsun-Kong (T.K.) Sham
University of Western Ontario

 

 "Probing Electronic and Chemical Properties of Nanomaterials - the Interplay of Synchrotron Radiation Spectroscopy, Morphology and Electronic Structures"

Abstract:  Professor T.K. Sham’s research is concerned with the Chemistry and Physics of materials and the development and application of synchrotron radiation, especially the interplay of electronic structure, materials properties and synchrotron techniques. His areas of expertise include nanomaterial synthesis, surface and interface, photoemission, x-ray absorption, photon-in photon-out spectroscopy (x-ray emission, x-ray excited optical luminescence, resonant and non-resonant inelastic x-ray scattering via the x-ray and the Auger channel) and x-ray microscopy. He has published over 360 papers and has presented many talks worldwide. In 2010 he received the J.C. Polanyi Award of the Canadian Society for Chemistry.

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NOTE: Time

Friday, April 8, 2011
TIME:  2PM

Presentation:  pdf

 

Marit Klein, Karlsruhe Institute of Technology

 

 "Coherent Synchrotron Radiation at ANKA"

Abstract:  ANKA is a storage ring light source with a circumference of 110 m and a maximum beam energy of 2.5 GeV. It is operated on a regular basis with low momentum compaction (low-alpha) lattices to produce short bunches for the generation of coherent synchrotron radiation (CSR) in the THz range. To enable CSR emission, the bunch length has to be shorter than or equal to the generated radiation wavelength. The CSR production significantly enhances the radiation power of frequencies in the far infrared / THz range. Dependig on the respective users' demand, the appropriate electron beam and lattice parameters are chosen. Detailed studies of these parameters have been performed. This presentation shows results of the CSR characterization as well as beam based modeling of the low-alpha lattices.

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NOTE: Time

Friday, April 1, 2011
TIME:  10:00am

Peter Leban, Instrumentation Technologies
Libera Brilliance and Libera Photon

 

 "Storage Ring BPMs"

 

Abstract:  Libera instrument family is a worldwide used in synchrotron light sources such as: ESRF, PETRA-III, Diamond Light Source, Soleil, SSRF, Taiwan Light Source and many others. Electron beam position processors, Libera Brilliance and its versions, offer users smooth machine commissioning, detailed machine physics studies with submicron resolution and fast feedback building and slow monitoring. During the seminar, general introduction to the basic and advanced measuring and performance features will be presented. The seminar will also include set up and configuration of the unit, live demonstration of data acquisitions as well as suggestions for different operation modes (machine studies, orbit monitoring and fast orbit feedback control).

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Friday, April 1, 2011

 Qun Liu, Brookhaven National Laboratory

 

Presentation:  ppt (login required)

 "Multi-crystal Anomalous Diffraction for Macromolecular Phasing"

 

Abstract:  Anomalous diffraction signals have been widely used for macromolecular phasing. Phase evaluations from anomalous diffraction data typically require the acquisition and analysis of weak anomalous signals. However due to factors such as poor intrinsic order, radiation damage, inadequate anomalous scatterers, poor diffraction quality and other noise-causing factors, anomalous signals from a single crystal are not always adequate for structure determination. With an assumption that the weak anomalous signals may be more accurately extracted from multiple crystals, multi-crystal data merging and analyses were made for SeMet (SeMet-SAD phasing) as well as native (sulfur-SAD phasing) proteins. We demonstrate that structure determinations are possible when no single crystal is sufficient. Anomalous signals, success in substructure determinations and phase accuracy all improve with the increase of the number of crystals in the data merging. We propose that such multi-crystal strategies may be broadly useful for solving challenging macromolecular structures, for example macromolecular complexes and membrane proteins, when only weak anomalous signals are available.

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Friday, March 25, 2011

 

 Fabio Casagrande, Oak Ridge National Laboratory

 

 

 "SNS Cryogenic Systems"

Abstract:  The SNS cryogenic system provides 2K cooling to the SNS Superconducting Linac. The system has been in operation non stop in different modes with very high availability since 2004.

I will talk about the system design basis, the commissioning phase, lessons learned and the current operation. I will close the talk going over current and future cryogenic projects at SNS.

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Friday, March 18, 2011

 

Jonathan Wurtele, Physics Department
University of California at Berkeley

 

"X-ray Free-Electron Lasers Based on Superconducting Linacs"

 

Abstract:  X-ray Free Electron Laser (FEL) facilities at FLASH (Germany) and the LCLS (USA) reliably produce orders of magnitude more coherent x-ray power than conventional synchrotrons. Buoyed by these results, many groups around the world are either developing plans for or building x-ray FELs. A soft x-ray FEL driven by a ~2 GeV beam is being investigated [1] at the Lawrence Berkeley National Laboratory based on superconducting RF technology operating in CW mode. The electron bunches will be produced at repetition rates of 1MHz or higher provided to users at a suite of up to 10 FELs. I will give a brief overview of the advantages of these technology and configuration choices, and describe key accelerator and FEL physics challenges. The possibility of operation at repetition rates above ~10MHz opens up the exploration of FEL soft x-ray oscillators. I will discuss the “echo-oscillator” FEL [2], where FEL oscillators are used to produce the power needed to seed the electron bunches in an echo-enhanced FEL [3]. In this scheme, longitudinal coherence is achieved at high repetition rate without requiring external seeding.

[1] J. Corlett, et al., “A Next Generation Light Source Facility at LBNL”, Paper TUODS2, PAC 2011
[2] J. Wurtele et al., “Tunable soft x-ray oscillators", Paper TUOCI2 Proceedings of the 32nd International Free Electron Laser Conference (2010)
[3] G. Kov, Phys. Rev. Lett. 102, 074801 (2009)

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Friday, March 11, 2011

Presentation:  ppt / pdf

John Spence, Physics Department
Arizona State University

 

"Femtosecond Nanodiffraction using a Hard X-ray Laser - toward the molecular movie"

 

Abstract:  A summary of recent results will be presented from the Linac Coherent Light Source (LCLS) at Stanford, the first hard X-ray laser. This produces 1- 8 kV pulses of X-rays of 10 -300 fs duration in a 3 micron beam, which we have use to obtain diffraction patterns from millions of submicron Photosystem I (PS I), PS II and PSI-ferredoxin, protein nanocrystals [1] prepared in the Fromme lab at ASU, and from individual viruses [2]. These are supplied fully hydrated in a liquid jet [3] running in vacuum across the LCLS beam. We study the diffract-and-destroy mechanism in which a useful diffraction pattern is formed before the nanocrystal is vaporised. In this way radiation damage of delicate membrane proteins is avoided. Each pulse produces one pattern from one randomly oriented nanocrystal, which is read out, and the process repeated at 60 Hz. We have assesed the quality of the data by comparison with synchrotron data. Data analysis for these partial reflections, [4,5] and new solutions to the phase problem are discussed [6]. These are based on the interference fringes between Bragg reflections resulting from the spatial coherence of the LCLS. I will also discuss preliminary time-resolved pump-probe experiments on PS I-ferredoxin (undocking), using this apparatus, and our very recent LCLS nanoxtal experiments using 9 kV X-rays , which produced near-atomic resolution from proteins. Experiments using correlations and fluctuations in "snap-shot" SAXS patterns are also reviewed [7], in which an image of one particle has been reconstructed using the scattering from many randomly oriented identical particles, ab initio, without modelling. A workshop on X-ray lasers in Biology was held in Berkeley from Jan 18, 2011. See https://sites.google.com/a/lbl.gov/biology-with-fels/ for powerpoints.

*and the SLAC/CFEL Hamburg/Heidelburg MPI/ASU collaboration.
1. Chapman et al Nature, 470, 73. (2011) for a full author list
2. Seibert et al Nature. 470, 78 (2011)
3. De Ponte et al J. Phys D 41, 195505 (2008)
4. Kirian, Spence et al Optics Express 18, 5713 (2010)
5. Kirian, et al. Acta Cryst A (2010). Submitted
6. Spence et al Optics Express 19, 2866 (2011)
7. Saldin, Spence et al. New J. Phys. 12, 035014 (2010). PRL in press

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March 8th LASSP Seminar - Pierre Thibault
"X-ray Imaging in the Style of Bird Calls"

Presentation:  pdf

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NOTE: Day

Wednesday, March 2, 2011

Presentation:  pptx / pdf

 

Robert Fischetti, Assoc Director NIGMS/National Cancer Inst. Collaborative Access Team
Biosciences Division, Argonne National Laboratory

 

"Radiation Damage to Protein Crystals is Reduced with Micron-Sized X-ray Beams"

Abstract:  Radiation damage is a major limitation in crystallography of biological macromolecules, even for cryo-cooled samples, and is particularly acute in micro-diffraction. For the X-ray energies most commonly used for protein crystallography at synchrotron sources, photoelectrons are the predominant source of radiation damage. If the beam size is small relative to the photoelectron path length, then the photoelectron may escape the beam footprint, resulting in less damage in the illuminated volume. Thus, it may be possible to exploit this phenomenon to reduce radiation-induced damage during data measurement for techniques such as diffraction, spectroscopy and imaging that use X-rays to probe both crystalline and non-crystalline biological samples. I will present the results of the first experimental demonstration of reduced radiation damage in protein crystals with small beams where damage was measured as a function of micron-sized X-ray beams of decreasing dimensions. The damage rate normalized for dose was reduced by a factor of 3 from the largest (15.6 µm) to the smallest (0.84 µm) X-ray beam used. In addition, radiation-induced damage to protein crystals was mapped parallel and perpendicular to the polarization direction of an incident 1- µm X-ray beam. The observed damage was greatest at the beam center and decreased monotonically to zero at a distance of about 4 μm, establishing the range of photoelectrons. The damage is less anisotropic than photoelectron emission probability, consistent with photoelectron trajectory simulations. The experimental results provide the basis for data collection protocols to mitigate with micron-sized X-ray beams the effects of radiation damage.

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!!CANCELLED!!  NOTE: Time

Friday, February 25, 2011
Time: 2:00pm

Frank Marhauser,
Jefferson Lab

 

"JLab SRF Cavity Fabrication Errors, Consequences and Lessons Learned"

Abstract:  Elliptical superconducting RF cavities are preferably made today from deep drawn niobium sheets as pursued at Jefferson Laboratory (JLab). The fabrication of a cavity incorporates various cavity cell machining, trimming and electron beam welding steps as well as surface chemistry that add to forming errors creating geometrical deviations of the cavity shape from its design. An analysis of in-house built cavities over the last years revealed significant errors in cavity production with severe consequences. Improved methods have been applied successfully for the most recent non-R&D, production style cryomodule cavities to meet required performance criteria. Details will be given in this talk.

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Friday, February 18, 2011

Presentation:  ppt / pdf

 Vadim Dudnikov, Muons, Inc.

 "Diagnostics for Observation and Damping of E-P Instability"

Abstract:  Clearing electrodes, fast gauges, fast valves, fast extractors, repulsing electrodes, electron and ion collectors with retarding grids, particles spectrometers using for detection of secondary particles generation and secondary particles identification will be discussed. Features of electrostatic and magnetic dipole and quadrupole pickups will be presented. An influence of nonlinear generation of secondary plasma in driving and stabilization of e-p instability is discussed. Observations of anomaly in secondary particles generation will be presented.

Conditions for accumulation of proton beam with intensity greater than space charge limit will be discussed.

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NOTE: Day and Time

Monday, February 14, 2011
Time: 2:30pm

Bruce Carlsten,
Los Alamos National Laboratory

 

"Eigen-emittances and Emittance Exchangers"

 

Abstract:  Eigen-emittances are constants of linear symplectic motion (like in an accelerator). By forming the correct eigen-emittances when an electron beam is formed, it may be possible to achieve extraordinarily bright electron beams, suitable for X-ray free-electron lasers at reduced beam energies. One of the key tools used for recovering eigen-emittances is the emittance exchanger, recently demonstrated experimentally at Fermilab. We additionally discuss the possibility of using an emittance exchanger as a bunch compressor, which has novel features such as no initial or residual energy-phase correlation is required and that the micro-bunch instability is suppressed.

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Friday, February 4, 2011

 

Eric Dufresne
APS

 

"Plans to Develop a Picosecond Source and Beamlines in the APS Upgrade"

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Friday, January 28, 2011

Presentation:  pdf

Lee Makowski, Northeastern

 

"Probing Protein Ensembles with X-ray Solution Scattering"

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NOTE: Day

Monday, January 24, 2011

 Steve Wang, Advanced Photon Source, Argonne National Laboratory

 "In Situ Dynamic Nano-CT Imaging at APS"

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Friday, January 21, 2011

Presentation:  pdf (login required)

 Sarvjit Shastri, Advanced Photon Source, Argonne National Laboratory

 "Short pulse X-ray Optics:  Effects and Considerations"

Abstract:  Given the desire to use short x-ray pulses, ranging in duration from picoseconds to femtoseconds, from sources like SASE- and seeded-XFELs, ERLs, and XFELOs for time-resolved studies of fast processes, temporal broadening phenomena encountered by such pulses in propagating through optics are important. Since perfect crystals will continue to serve as valuable tools to manipulate hard x-ray beams, effects pertaining to perfect crystal diffraction (i.e., dynamical diffraction theory) with short incident pulses will be presented: impulse responses in Bragg geometry, photon "echos" in thin crystals, temporal "pendellosung" in Laue geometry, forward diffracted "wakefields" and seeding, multiple crystals, longitudinal shear in asymmetric reflections, compensation effects, and the alteration of a SASE-XFEL source's temporal structure following monochromatization. Optics possibilities to further compress x-ray pulses, operating in conjunction with accelerator schemes like energy-chirping and rf-deflection of various sources, will be discussed. Temporal broadening effects in imperfect/distorted crystals and focusing elements (curved mirrors, refractive optics) will also be mentioned.

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NOTE: Day and Time

Wednesday, January 5, 2011
Time: 2:00pm

 

Kenneth Evans-Lutterodt, Physicist
National Synchrotron Light Source

 

"Microfabrication of Hard X-ray Optics for Advanced X-ray Sources"

Abstract:  New and improved sources of hard X-rays are enabling advances in materials characterization, and these advances lead to better understanding of the materials systems. Spatially resolved diffraction with small spots, 3D tomography and phase contrast imaging are a few examples of the new characterization methods. Using microfabrication methods, we have fabricated a number of different optics that can take advantage of these new sources. One class of optics, kinoform lenses have been shown to focus to below 100nm, with photon energies as high as 30keV, and as low as 7.35keV, and can also be large enough to collect all the light from the brighter 3rd generation sources. We have also microfabricated bi-prisms to perform a virtual Young's double slit experiment, and deduce the transverse coherence length of the source from the interference patterns. Finally, we use phase retrieval methods to measure the size of a focused spot, in anticipation of measuring spot sizes in the sub-10nm range that will be difficult to measure with conventional methods.

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