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Field Errors in Hybrid Insertion Devices

Description: Hybrid magnet theory as applied to the error analyses usedin the design of Advanced Light Source (ALS) insertion devices isreviewed. Sources of field errors in hybrid insertion devices arediscussed.
Date: February 3, 1995
Creator: Schlueter, R.D.
Partner: UNT Libraries Government Documents Department

Resonant soft X-ray emission spectroscopy of liquids

Description: We present now a possible way to carry out soft-x-rayfluorescence spectroscopy of liquids. The liquid cell has a window toattain compatibility with UHV conditions of the spectrometer andbeamline, The synchrotron radiation enters the liquid cell through a 100nm-thick silicon nitride window and the emitted xrays exit through thesame window. This allows in particular liquid solid interfaces to bestudied. Such a liquid cell has been used to study the electronicstructure of a variety of systems ranging from water solutions ofinorganic salts and inertial drugs to nano materials and actinidecompounds in their wet conditions.
Date: October 27, 2004
Creator: Guo, J.-H.; Augustsson, A.; Englund, C.-J. & Nordgren, J.
Partner: UNT Libraries Government Documents Department

Microstructure evolution of tin under electromigration studied bysynchrotron X-Ray micro-diffraction

Description: Under constant current electromigration, white tin(?-Sn)exhibited a resistance drop of up to 10 percent. It has a body centertetragonal (BCT) structure, and the resistivity along the aand b axes is35 percent smaller than that along the c axis.Microstructure evolutionunder electromigration could be responsible for the resistance drop.Synchrotron radiation white beam x-ray microdiffraction was used to studythis evolution. Both stress and grain orientation was studied.Grain-by-grain analysis was obtained from the diffracted Laue patternsabout the changes of grain orientation during electromigration testing inex-situ and in-situ samples. We observed that high resistance grainsreorient with respect to the neighboring low resistance grains, mostlikely by grain rotation of the latter. A different mechanism ofmicrostructure evolution under electromigration from the normal graingrowth is proposed and discussed.
Date: May 5, 2005
Creator: Wu, Albert T.; Lloyd, J.R.; Tamura, N. & Tu, K.-N.
Partner: UNT Libraries Government Documents Department

Correlation between exchange bias and pinned interfacialspins

Description: Using x-ray magnetic circular dichroism, we have detectedthe very interfacial spins that are responsible for the horizontal loopshift in three different exchange bias sandwiches, chosen because oftheir potential for device applications. The "pinned" uncompensatedinterfacial spins constitute only a fraction of a monolayer and do notrotate in an external magnetic field since they are tightly locked to theantiferromagnetic lattice. A simple extension of the Meiklejohn and Beanmodel is proposed to account quantitatively for the exchange bias fieldsin the three studied systems from the experimentally determined number ofpinned moments and their sizes.
Date: July 1, 2003
Creator: Ohldag, H.; Scholl, A.; Nolting, F.; Arenholz, E.; Maat, S.; Young, A.T. et al.
Partner: UNT Libraries Government Documents Department

Crossed elliptical polarization undulator

Description: The first switching of polarization direction is possible by installing two identical helical undulators in series in a same straight section in a storage ring. By setting each undulator in a circular polarization mode in opposite handedness, one can obtain linearly polarized radiation with any required polarization direction depending on the modulator setting between two undulators. This scheme can be used without any major degradation of polarization degree in any low energy low emittance storage ring.
Date: May 1997
Creator: Sasaki, Shigemi
Partner: UNT Libraries Government Documents Department

Rigid, adjustable support of aligned elements via six struts

Description: At particle accelerators around the world, a great deal of effort is expended on determining precise component locations in space. Much less effort is spent on the design of systems to precisely and solidly locate these components in space, once one has the ability to know where they are. Unfortunately, there are many inadequate ways of adjustably mounting position sensitive beam line hardware, and only a few methods which work well. Traditional jacking screw and shimming support systems are often troublesome, and a drain on manpower and time. Multiple precision stages of adequate capacity for heavy items are expensive. At Lawrence Berkeley National Laboratory's Advanced Light Source, the authors rely almost exclusively on their home-grown, simple, and cost effective six-strut mechanical support systems. This approach meets the seismic requirements, minimizes vibration, and allows easy and precise alignment of a wide variety of accelerator hardware.
Date: October 1, 1997
Creator: Thur, W.; Lauritzen, T.; DeMarco, R.; Baldock, B. & Rex, K.
Partner: UNT Libraries Government Documents Department

Advanced Light Source Activity Report 2002

Description: This annual report of the Advanced Light Source details science highlights and facility improvements during the year. It also offers information on events sponsored by the facility, technical specifications, and staff and publication information.
Date: June 12, 2003
Creator: Duque, Theresa; Greiner, Annette; Moxon, Elizabeth; Robinson, Arthur & Tamura, Lori (Editors)
Partner: UNT Libraries Government Documents Department

ALSNews 2007

Description: Compilation of Advanced Light Source newsletter, ALSNews, for 2007, Volumes 272-282.
Date: November 28, 2007
Creator: McCullough (Ed.), Julie & Tamura (Ed.), Lori
Partner: UNT Libraries Government Documents Department

ALSNews 2008

Description: Compilation of Advanced Light Source newsletter, ALSNews, for 2008, Volumes 283-293.
Date: November 26, 2008
Creator: McCullough (Ed.), Julie & Tamura (Ed.), Lori
Partner: UNT Libraries Government Documents Department

ALSNews 2009

Description: Compilation of Advanced Light Source newsletter, ALSNews, for 2009, Volumes 294-304.
Date: November 25, 2009
Creator: Tamura (Ed.), Lori
Partner: UNT Libraries Government Documents Department

Elimination of 'ghost'-effect-related systematic error in metrology of X-ray optics with a long trace profiler

Description: A data acquisition technique and relevant program for suppression of one of the systematic effects, namely the ''ghost'' effect, of a second generation long trace profiler (LTP) is described. The ''ghost'' effect arises when there is an unavoidable cross-contamination of the LTP sample and reference signals into one another, leading to a systematic perturbation in the recorded interference patterns and, therefore, a systematic variation of the measured slope trace. Perturbations of about 1-2 {micro}rad have been observed with a cylindrically shaped X-ray mirror. Even stronger ''ghost'' effects show up in an LTP measurement with a mirror having a toroidal surface figure. The developed technique employs separate measurement of the ''ghost''-effect-related interference patterns in the sample and the reference arms and then subtraction of the ''ghost'' patterns from the sample and the reference interference patterns. The procedure preserves the advantage of simultaneously measuring the sample and reference signals. The effectiveness of the technique is illustrated with LTP metrology of a variety of X-ray mirrors.
Date: April 28, 2005
Creator: Yashchuk, Valeriy V.; Irick, Steve C. & MacDowell, Alastair A.
Partner: UNT Libraries Government Documents Department

Domain-size-dependent exchange bias in Co/LaFeO3

Description: X-ray microscopy using magnetic linear dichroism of a zero-field-grown, multi-domain Co/LaFeO{sub 3} ferromagnet/antiferromagnet sample shows a local exchange bias of random direction and magnitude. A statistical analysis of the local bias of individual, micron-size magnetic domains demonstrates an increasing bias field with decreasing domain size as expected for a random distribution of pinned, uncompensated spins, which are believed to mediate the interface coupling. A linear dependence with the inverse domain diameter is found.
Date: September 22, 2004
Creator: Scholl, A.; Nolting, F.; Seo, J.W.; Ohldag, H.; Stohr, J.; Raoux,S. et al.
Partner: UNT Libraries Government Documents Department

Interlayer Interaction and Electronic Screening in MultilayerGraphene

Description: The unusual transport properties of graphene are the direct consequence of a peculiar bandstructure near the Dirac point. We determine the shape of the {pi} bands and their characteristic splitting, and find the transition from two-dimensional to bulk character for 1 to 4 layers of graphene by angle-resolved photoemission. By detailed measurements of the {pi} bands we derive the stacking order, layer-dependent electron potential, screening length and strength of interlayer interaction by comparison with tight binding calculations, yielding a comprehensive description of multilayer graphene's electronic structure.
Date: June 7, 2007
Creator: Ohta, Taisuke; Bostwick, Aaron; McChesney, J.L.; Seyller, Thomas; Horn, Karsten & Rotenberg, Eli
Partner: UNT Libraries Government Documents Department

Soft X-ray spectromicroscopy and its application to semiconductor microstructure characterization

Description: The universal trend towards device miniaturization has driven the semiconductor industry to develop sophisticated and complex instrumentation for the characterization of microstructures. Many significant problems of relevance to the semiconductor industry cannot be solved with conventional analysis techniques, but can be addressed with soft x-ray spectromicroscopy. An active spectromicroscopy program is being developed at the Advanced Light Source, attracting both the semiconductor industry and the materials science academic community. Examples of spectromicroscopy techniques are presented. An ALS {mu}-XPS spectromicroscopy project is discussed, involving the first microscope completely dedicated and designed for microstructure analysis on patterned silicon wafers.
Date: May 1, 1996
Creator: Gozzo, F.; Franck, K.; Howells, M.R. & Hussain, Z.
Partner: UNT Libraries Government Documents Department

Commissioning of the advanced light source dual-axis streak camera

Description: A dual-axis camera, Hamamatsu model C5680, has been installed on the Advanced Light Source photon-diagnostics beam-line to investigate electron-beam parameters. During its commissioning process, the camera has been used to measure single-bunch length vs. current, relative bunch charge in adjacent RF buckets, and bunchphase stability. In this paper the authors describe the visible-light branch of the diagnostics beam-line, the streak-camera installation, and the timing electronics. They will show graphical results of beam measurements taken during a variety of accelerator conditions.
Date: May 1997
Creator: Hinkson, J.; Keller, R. & Byrd, J.
Partner: UNT Libraries Government Documents Department

Model calibration and symmetry restoration of the advanced light source

Description: The symmetry of the ALS magnetic lattice is crucial in suppressing nonlinear structural resonances. Breaking the symmetry of the lattice can lead to a reduction in the dynamic aperture. The degree of symmetry breaking can be determined by fitting a magnetic lattice model to the measured orbit response matrix. This reveals a large beating of the vertical beta-function caused mainly by gradient errors in the QD quadrupole magnets. When the quadrupole field strengths are adjusted to compensate for the gradient errors, the symmetry of the lattice is restored. The new lattice has a larger dynamic aperture and an improved injection efficiency.
Date: June 10, 1996
Creator: Robin, D.; Portmann, G.; Nishimura, H. & Safranek, J.
Partner: UNT Libraries Government Documents Department

Electron beam diagnostics using synchrotron radiation at the Advanced Light Source

Description: Synchrotron light emitted from a bend magnet is being used to diagnose the electron beam stored in the main accelerator of the Advanced Light Source (ALS) at Berkeley Lab. The radiation has maximum intensity in the soft X-ray region and is imaged by a Kirkpatrick-Baez mirror pair from the source point inside the ring onto a Bismuth/Germanium-Oxide (BGO) crystal, converted into visible light and magnified by an attached microscope. The final image is captured by a TV camera-tube and digitized by a frame- grabber device to obtain records of parameters such as beam size, center location and profile. Data obtained from this Diagnostic Beam Line have been very useful in day-to-day operation of the ALS storage ring to assess the quality and repeatability of the stored beam. The line has further been utilized in several dedicated research activities to measure bunch lengths under various conditions and observe transverse beam instabilities. A summary of obtained results is given in this paper , together with a description of the technical features of the Diagnostic Beam Line.
Date: May 1996
Creator: Keller, R.; Renner, T. & Massoletti, D. J.
Partner: UNT Libraries Government Documents Department