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588 results on '"Padmore, H."'

58. Initial feasibility study of a dedicated synchrotron radiation light source for ultrafast X-ray science

Author

Corlett, John N., primary, DeSantis, S., additional, Hartman, N., additional, Heimann, P., additional, LaFever, R., additional, Li, D., additional, Padmore, H., additional, Rimmer, R., additional, Robinson, K., additional, Schoenlein, R., additional, Tanabe, J., additional, Wang, S., additional, Zholents, A., additional, and Kairan, D., additional

Published
2001
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60. Future Plans for X-Ray Microscopy at the SRS

Author

Padmore, H. A., Duke, P. J., Burge, R. E., Michette, A. G., Tamir, Theodor, editor, Lotsch, Helmut K. V., editor, Sayre, David, editor, Kirz, Janos, editor, Howells, Malcolm, editor, and Rarback, Harvey, editor

Published
1988
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65. Dependence on Crystal Size of the Nanoscale Chemical Phase Distribution and Fracture in LixFePO4

Author

Yu, YS, Kim, C, Shapiro, DA, Farmand, M, Qian, D, Tyliszczak, T, Kilcoyne, ALD, Celestre, R, Marchesini, S, Joseph, J, Denes, P, Warwick, T, Strobridge, FC, Grey, CP, Padmore, H, Meng, YS, Kostecki, R, and Cabana, J

Abstract

© 2015 American Chemical Society. The performance of battery electrode materials is strongly affected by inefficiencies in utilization kinetics and cycle life as well as size effects. Observations of phase transformations in these materials with high chemical and spatial resolution can elucidate the relationship between chemical processes and mechanical degradation. Soft X-ray ptychographic microscopy combined with X-ray absorption spectroscopy and electron microscopy creates a powerful suite of tools that we use to assess the chemical and morphological changes in lithium iron phosphate (LiFePO4) micro- and nanocrystals that occur upon delithiation. All sizes of partly delithiated crystals were found to contain two phases with a complex correlation between crystallographic orientation and phase distribution. However, the lattice mismatch between LiFePO4 and FePO4 led to severe fracturing on microcrystals, whereas no mechanical damage was observed in nanoplates, indicating that mechanics are a principal driver in the outstanding electrode performance of LiFePO4 nanoparticles. These results demonstrate the importance of engineering the active electrode material in next generation electrical energy storage systems, which will achieve theoretical limits of energy density and extended stability. This work establishes soft X-ray ptychographic chemical imaging as an essential tool to build comprehensive relationships between mechanics and chemistry that guide this engineering design.

Published
2015
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68. Multiplexed high resolution soft x-ray RIXS

Author

Chuang, Y.-D., primary, Anderson, C., additional, Benk, M., additional, Goldberg, K., additional, Voronov, D., additional, Warwick, T., additional, Yashchuk, V., additional, and Padmore, H. A., additional

Published
2016
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69. The VHF-Gun, the LBNL High-Brightness Electron Photo-Injector for MHz-Class Repetition-Rate Applications*

Author

Sannibale, F., primary, Baptiste, K., additional, Cork, C., additional, Corlett, J., additional, Decool, M., additional, De Santis, S., additional, Dickinson, M., additional, Doolittle, L., additional, Doyle, J., additional, Feng, J., additional, Filippetto, D., additional, Gibson, D., additional, Giermann, S., additional, Harris, G., additional, Huang, G., additional, Johnson, M., additional, Kirkpatrick, M., additional, Kramasz, T., additional, Kwiatkowski, S., additional, Leitner, D., additional, Lellinger, R., additional, Li, R., additional, Mitchell, C., additional, Moroz, V., additional, Nasiatka, J., additional, Norum, W. E., additional, Padmore, H., additional, Pagani, C., additional, Portmann, G., additional, Qian, H., additional, Rasool, H., additional, Schmerge, J., additional, Sertore, D., additional, Syversrud, D., additional, Vecchione, T., additional, Vinco, M., additional, Virostek, S., additional, Wells, R., additional, Zhou, F., additional, and Zolotorev, M., additional

Published
2016
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72. XPS and UHV AFM Analysis of the K2CsSb Photocathodes Growth

Author

Schubert, S., Smedley, J., Rao, T., Ruiz Os s, M., Liang, X., Ben Zvi, I., Padmore, H., and Vecchione, T.

Subjects
Large scale facilities for research with photons neutrons and ions
Abstract

Next generation light sources, based on Energy Recovery Linac and Free Electron Laser technology will rely on photoinjector based electron sources. Successful operation of such sources requires reliable photocathodes with long operational life, uniform and high quantum efficiency, low thermal emittance and low dark current. The goal of this project is to construct a cathode which meets these requirements. Advances in photocathode research must take a combined effort. The materials have to be analyzed by means of chemical composition, surface structure and these findings have to be correlated to the quantum efficiency and performance in the injector. The presented work focuses on the chemical composition and surface structure of K2CsSb photocathodes. The XPS and AFM measurements were performed at the Center of Functional Nanomaterials at BNL. K2CsSb photocathodes were grown under UHV conditions. The components were adsorbed one at a time and after each growth step the corresponding XPS spectra was taken. During growth the quantum efficiency was recorded. As last step the sample was moved into the AFM without exposure to air to determine the surface roughness

Published
2013

73. Exploring the microscopic origin of exchange bias with photoelectron emission microscopy (invited).

Author

Scholl, A., Nolting, F., Sto¨hr, J., Regan, T., Lu¨ning, J., Seo, J. W., Locquet, J.-P., Fompeyrine, J., Anders, S., Ohldag, H., and Padmore, H. A.

Subjects
MAGNETISM, FERROMAGNETISM, ANTIFERROMAGNETISM, ANISOTROPY, ELECTRON spectroscopy
Abstract

It is well known that magnetic exchange coupling across the ferromagnet-antiferromagnet interface results in an unidirectional magnetic anisotropy of the ferromagnetic layer, called exchange bias. Despite large experimental and theoretical efforts, the origin of exchange bias is still controversial, mainly because detection of the interfacial magnetic structure is difficult. We have applied photoelectron emission microscopy (PEEM) on several ferromagnet-antiferromagnet thin-film structures and microscopically imaged the ferromagnetic and the antiferromagnetic structure with high spatial resolution. Taking advantage of the surface sensitivity and elemental specificity of PEEM, the magnetic configuration and critical properties such as the Néel temperature were determined on LaFeO[sub 3] and NiO thin films and single crystals. On samples coated with a ferromagnetic layer, we microscopically observe exchange coupling across the interface, causing a clear corresponde! nce of the domain structures in the adjacent ferromagnet and antiferromagnet. Field dependent measurements reveal a strong uniaxial anisotropy in individual ferromagnetic domains. A local exchange bias was observed even in not explicitly field-annealed samples, caused by interfacial uncompensated magnetic spins. These experiments provide highly desired information on the relative orientation of electron spins at the interface between ferromagnets and antiferromagnets. © 2001 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Published
2001
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75. Status of the APEX Project at LBNL

Author

Naval Postgraduate School (U.S.), Physics, Sannibale, F., Bailey, B., Baptiste, K., Byrd, J., Cork, C., Corlett, J., De Santis, S., Dimaggio, S., Doolittle, L., Doyle, J., Emma, P., Feng, J., Filippetto, D., Garcia Quintas, D., Huang, G., Huang, H., Kramasz, T., Kwiatkoswski, S., Norum, W.E., Padmore, H., Papadopoulos, C.F., Pappas, C., Portmann, G., Qiang, J., Staples, J., Vecchione, T., Venturini, M., Vinco, M., Wan, W., Wells, R., Zolotorev, M., Zucca, F., Prantil, M., Messerly, M., Pogue, C., Naval Postgraduate School (U.S.), Physics, Sannibale, F., Bailey, B., Baptiste, K., Byrd, J., Cork, C., Corlett, J., De Santis, S., Dimaggio, S., Doolittle, L., Doyle, J., Emma, P., Feng, J., Filippetto, D., Garcia Quintas, D., Huang, G., Huang, H., Kramasz, T., Kwiatkoswski, S., Norum, W.E., Padmore, H., Papadopoulos, C.F., Pappas, C., Portmann, G., Qiang, J., Staples, J., Vecchione, T., Venturini, M., Vinco, M., Wan, W., Wells, R., Zolotorev, M., Zucca, F., Prantil, M., Messerly, M., and Pogue, C.

Abstract

The Advanced Photo-injector Experiment (APEX) at the Lawrence Berkeley National Laboratory is focused on the development of a high-brightness high-repetition rate (MHz-class) electron injector for X-ray FEL applications. The injector is based on a new concept gun, utilizing a normal conducting 186 MHz RF cavity operating in CW mode in conjunction with high quantum efficiency photocathodes capable of delivering the required repetition rates with available laser technology. The APEX activities are staged in 3 main phases. In Phases 0 and I, the gun is tested at its nominal energy of 750 keV and several different photocathodes are tested at full repetition rate. In Phase II, a pulsed linac is added for accelerating the beam at several tens of MeV to reduce space charge effects and measure the high-brightness performance of the gun when integrated in an injector scheme. At Phase II energies, the radiation shielding configuration of the bunker where APEX is located limits the repetition rate to a maximum of several Hz. Phase 0 is under commissioning, Phase I components under fabrication, and initial activities for Phase II are underway. This paper presents an update on the status of all these activities.

Published
2014

76. Picosecond soft x-ray absorption measurement of the photoinduced insulator-to-metal transition in VO2

Author

Cavalleri, A, Chong, H, Fourmaux, S, Glover, T, Heimann, P, Kieffer, J, Mun, B, Padmore, H, and Schoenlein, R

Subjects
Physics, Materials Sciences, Condensed Matter::Strongly Correlated Electrons, femtosecond x-ray VO2 correlated electron
Abstract

We directly measure the photoinduced insulator-to-metal transition in VO2 using time-resolved near-edge x-ray absorption. Picosecond pulses of synchrotron radiation are used to detect the redshift in the vanadium L3edge at 516 eV, which is associated with the transient collapse of the low-temperature band gap. We identify a two-component temporal response, corresponding to an ultrafast transformation over a 50 nm surface layer, followed by 40 m/s thermal growth of the metallic phase into the bulk.

Published
2004

78. Electron emission processes in photocathodes and dynodes

Author

Smedley, J., primary, Schubert, S., additional, Xie, J., additional, Ruiz-Oses, M., additional, Liang, X., additional, Muller, E., additional, Padmore, H., additional, Wong, J., additional, Hulbert, S., additional, Theulings, A. M. M. G., additional, Tao, S., additional, and van der Graaf, H., additional

Published
2014
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82. Microtexture and strain in electroplated copper interconnects

Author

Spolenak, R., Barr, D. L., Gross, M. E., Evans-Lutterodt, K., Brown, W. L., Nobumichi Tamura, Macdowell, A. A., Celestre, R. S., Padmore, H. A., Valek, B. C., Bravman, J. C., Flinn, P., Marieb, T., Keller, R. R., Batterman, B. W., and Patel, J. R.

Subjects
X-ray microdiffraction synchrotron thin film stress electromigration Cu interconnects texture advanced light source als, Materials Sciences
Abstract

The microstructure of narrow metal conductors in the electrical interconnections on IC chips has often been identified as of major importance in the reliability of these devices. The stresses and stress gradients that develop in the conductors as a result of thermal expansion differences in the materials and of electromigration at high current densities are believed to be strongly dependent on the details of the grain structure. The present work discusses new techniques based on microbeam x-ray diffraction (MBXRD) that have enabled measurement not only of the microstructure of totally encapsulated conductors but also of the local stresses in them on a micron and submicron scale. White x-rays from the Advanced Light Source were focused to a micron spot size by Kirkpatrick-Baez mirrors. The sample was stepped under the micro-beam and Laue images obtained at each sample location using a CCD area detector. Microstructure and local strain were deduced from these images. Cu lines with widths ranging from 0.8 mm to 5 mm and thickness of 1 mm were investigated. Comparisons are made between the capabilities of MBXRD and the well established techniques of broad beam XRD, electron back scatter diffraction (EBSD) and focused ion beam imagining (FIB).

Published
2001

83. Surface and bulk contribution to Cu(111) quantum efficiency

Author

Pedersoli, Emanuele, Greaves, C. M. R., Wan, W, Coleman Smith, C., Padmore, H. A., Pagliara, Stefania, Cartella, Andrea, Lamarca, Fabrizio, Ferrini, Gabriele, Galimberti, Gianluca, Montagnese, Matteo, Dal Conte, Stefano, Parmigiani, Fulvio, Pagliara, Stefania (ORCID:0000-0003-2966-3361), Ferrini, Gabriele (ORCID:0000-0002-5062-9099), Pedersoli, Emanuele, Greaves, C. M. R., Wan, W, Coleman Smith, C., Padmore, H. A., Pagliara, Stefania, Cartella, Andrea, Lamarca, Fabrizio, Ferrini, Gabriele, Galimberti, Gianluca, Montagnese, Matteo, Dal Conte, Stefano, Parmigiani, Fulvio, Pagliara, Stefania (ORCID:0000-0003-2966-3361), and Ferrini, Gabriele (ORCID:0000-0002-5062-9099)

Abstract

The quantum efficiency (QE) of Cu(111) is measured for different impinging light angles with photon energies just above the work function. We observe that the vectorial photoelectric effect, an enhancement of the QE due to illumination with light with an electric vector perpendicular to the sample surface, is stronger in the more surface sensitive regime. This can be explained by a contribution to photoemission due to the variation in the electromagnetic potential at the surface. The contributions of bulk and surface electrons can then be determined.

Published
2008

91. Bendable Kirkpatrick-Baez mirrors for the ALS micro-diffraction beamline 12.3.2: optimal tuning and alignment for multiple focusing geometries

Author

Yashchuk, V V, primary, Morrison, G Y, additional, Church, M, additional, Artemiev, N A, additional, Celestre, R, additional, Domning, E E, additional, Howells, M, additional, Kunz, M, additional, McKinney, W R, additional, Merthe, D J, additional, Smith, B V, additional, Tamura, N, additional, and Padmore, H A, additional

Published
2013
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92. Development of coherent scattering and diffractive imaging and the COSMIC facility at the Advanced Light Source

Author

Shapiro, D, primary, Roy, S, additional, Celestre, R, additional, Chao, W, additional, Doering, D, additional, Howells, M, additional, Kevan, S, additional, Kilcoyne, D, additional, Kirz, J, additional, Marchesini, S, additional, Seu, K A, additional, Schirotzek, A, additional, Spence, J, additional, Tyliszczak, T, additional, Warwick, T, additional, Voronov, D, additional, and Padmore, H A, additional

Published
2013
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99. Advanced photoinjector experiment photogun commissioning results

Author

Sannibale, F., primary, Filippetto, D., additional, Papadopoulos, C. F., additional, Staples, J., additional, Wells, R., additional, Bailey, B., additional, Baptiste, K., additional, Corlett, J., additional, Cork, C., additional, De Santis, S., additional, Dimaggio, S., additional, Doolittle, L., additional, Doyle, J., additional, Feng, J., additional, Garcia Quintas, D., additional, Huang, G., additional, Huang, H., additional, Kramasz, T., additional, Kwiatkowski, S., additional, Lellinger, R., additional, Moroz, V., additional, Norum, W. E., additional, Padmore, H., additional, Pappas, C., additional, Portmann, G., additional, Vecchione, T., additional, Vinco, M., additional, Zolotorev, M., additional, and Zucca, F., additional

Published
2012
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100. Advanced Light Source Update

Author

Tamura, L., primary, Hussain, Z., additional, Padmore, H. A., additional, Robin, D. S., additional, Bailey, S., additional, Feinberg, B., additional, and Falcone, R. W., additional

Published
2012
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