ISSN:0094-243X    

DOI:10.1063/1.54621

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

There are 23 insertion devices (IDs) at the APS now, and 17 of them have been installed and commissioned. Most of the IDs are 2.4-meter-long hybrid-type undulators with a 3.3 cm period. Two wigglers are used at the APS, one of them is an elliptical multipole wiggler with an electromagnet that produces alternate horizontal magnetic fields. All APS IDs have undergone fine magnetic tuning in order to minimize various integrals of the field through the ID for the whole range of IDs gaps, including the higher-order integrated multipole moments. Measurements of the particle-beam motion as the field strength of each ID was changed throughout its range found that the closed-orbit distortion agreed well with predictions based on magnetic measurement results. Radiation from the APS undulator has been characterized in terms of absolute spectral flux. Direct measurements of the positron beam emittance have been performed. In addition, the experimentally measured brilliance tuning curves for the APS undulator have been obtained. ©1997 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.54625

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

The Structural Biology Center (SBC) has developed and operates a sector (undulator and bending magnet) of the APS as a user facility for macromolecular crystallography. Crystallographically determined structures of proteins, nucleic acids and their complexes with proteins, viruses, and complexes between macromolecules and small ligands have become of central importance in molecular and cellular biology. Major design goals were to make the extremely high brilliance of the APS available for brilliance limited studies, and to achieve a high throughput of less demanding studies, as well as optimization for MAS-phasing. Crystal samples will include extremely small crystals, crystals with large unit cells (viruses, ribosomes, etc.) and ensembles of closely similar crystal structures for drug design, protein engineering, etc. Data are recorded on a 3000×3000 pixel CCD-area detector (optionally on image plates). The x-ray optics of both beamlines has been designed to produce a highly demagnified image of the source in order to match the focal size with the sizes of the sample and the resolution element of the detector. Vertical focusing is achieved by a flat, cylindrically bent mirror. Horizontal focusing is achieved by sagitally bending the second crystal of the double crystal monochromator. Monochromatic fluxes of 1.3*1013ph/s into focal sizes of 0.08 mm (horizontal)×0.04 mm (vertical) FWHM (flux density 3.5*1015ph/s/mm2) have been recorded.©1997 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.54578

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

We report the optical design and performance of the phase II inelastic scattering beamline at the National Synchrotron Light Source. The new beamline consists of a four-crystal Si(220) monochromator followed by a bent cylinder mirror. The monochromator is tunable from 5 to 10 keV with about 0.2 eV energy resolution throughout the tuning range. The size of the focused beam is about0.5 mm (H)×0.3 mm (V).©1997 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.54587

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

The design of a versatile ultrahigh vacuum (UHV) endstation for use at the Advanced Photon Source is described. The capabilities of the endstation include x-ray scatteringandx-ray spectroscopic techniques for the investigation of surfaces, interfaces, and thin films. The UHV analytical chamber also includes facilities for surface preparation, thin film growth, and standard (non-x-ray) surface analyses. The endstation, which is inspired by previous successful implementations for surface scattering, incorporates several novel design features to facilitate the use of both scattering and spectroscopic techniques, and also allows the examination of small samples. Its capabilities include x-ray reflectivity and crystal truncation rod studies, grazing-incidence x-ray diffraction, x-ray standing waves, surface extended x-ray absorption fine structure, x-ray holography, and x-ray photoelectron spectroscopy. ©1997 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.54588

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

The PNC-CAT has commissioned the front optics for its insertion device beamline at the APS, which enables experiments to be performed in the front optics station with monochromatic x-rays. The beamline consists of a liquid nitrogen cooled monochromator followed by a variety of focusing optics and is optimized for spectroscopic and microbeam applications. Two downstream experimental stations are under construction and will be equipped with microfocusing optics (Kirkpatrick-Baez mirrors and/or tapered capillary optics) to produce beams ranging from 0.1 to 20 microns with expected intensity of 1010–1011ph/sec/micron2; and with two UHV systems capable of MBE sample growth and combinedin-situstructural characterization by glancing-incidence XAFS, x-ray reflectivity, SEXAFS, XSW, and surface x-ray diffraction. The initial performance of the beamline and experimental activities will be reported.©1997 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.54614

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

The Biophysics Collaborative Access Team (BioCAT) project will be an outstanding research facility for biological small angle scattering, non-crystalline diffraction, and x-ray absorption spectroscopy at the Advanced Photon Source, Argonne National Labs. BioCAT operates as an NIH Research Resource under a cooperative agreement with NIH. BioCat has an aggressive program of core and collaborative research, service, and training. Central to the facility is the undulator beam line (designed by G. Rosenbaum, Argonne National Labs) capable of delivering ca. 1013–1014ph/s to the sample. Focusing optics will allow focal spot ranges from 1.5×3.5 mm to 30×80 micron, independently adjustable in the vertical and horizontal direction. Up to 8 m camera lengths can be accommodated in the 12m experimental enclosure. The accessible beam energy range will be from 3.5–13 keV using the undulator fundamental and 10–40 keV using the third harmonic. Energy resolution will exceed 2×10−4&Dgr;E/E. Detectors will include image plates, CCD detectors and some novel detectors designed to accommodate the high count rates expected at the APS. The multi-element detector will be a very high count-rate (up to 109ph/s global), one dimensional detector optimized for scattering applications. We are also developing a multilayer analyzer detector which maximizes solid angle of collection with high background rejection for biological spectroscopy applications.©1997 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.54618

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

The capabilities and performance of the variable groove density spherical grating monochromator have been extended through the installation of new gratings. Two new varied line spacing (VLS) gratings have been installed in the SRC High Energy Resolution Monochromator (HERMON). The specified polynomial variation in groove density was successfully fabricated on a blazed grating with a conventional ruling engine and on a laminar profile grating by ion beam etching. The theoretical resolving power of 5000 to 10000 is achieved in the energy ranges of 250 to 550 eV for the low energy laminar grating and 500 to 1100 eV for the high energy blazed grating. Experiments in magnetic circular dichroism are now possible with the implementation of a motorized water cooled aperture. The performance throughout the energy range is characterized by a variety of solid state and gas phase measurements. ©1997 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.54599

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

A time-of-flight mass spectrometer (TOFMS), has been designed and built at the Federal University of Rio de Janeiro (Brazil), with the aim of studying the ionic fragmentation of gas-phase compounds, using synchrotron radiation. Our main research interest consists on the observation of single, double and multiple ionization as a function of the incident photon energy, with particular emphasis on core-excited molecules. These processes are usually associated with the formation of very fast ions. The spectrometer employs, accordingly, a collimating lens which allows for the collection of ions having kinetic energies up to 40 eV with almost 100&percent; efficiency. By changing the lens voltage, the spectrometer can also be operated in a highly discriminating condition, which provides an easy and accurate method for the determination of the kinetic energy release. In order to be tested, the spectrometer was adapted to a brazilian beamline installed at CAMD (Center for Advanced Microstructures and Devices). Mass and coincidence (PEPICO, PIPICO and PEPIPICO) spectra were obtained, in the 12 to 310 eV photon energy range, for several compounds. A mass resolution (M/&Dgr;M) of 450 was attained at 132 a.m.u., with xenon. ©1997 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.54579

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

An undulator designed to be used for an x-ray free electron laser has to meet a set of stringent requirements. With no optical cavity, an x-ray FEL operates in the single pass Self Amplified Spontaneous Emission (SASE) mode; an electron macropulse is microbunched by an undulator and the radiation it creates. The microbunched pulse emits spontaneous radiation and coherent FEL radiation, whose power may reach saturation in a sufficiently long and perfect undulator. The pulse must have low emittance and high current, and its trajectory in the undulator must keep the radiation and the pulse together with a very high degree of overlap. We shall consider the case of the Linear Coherent Light Source (LCLS) FEL project at SLAC, which is intended to create 1.5 Å x-rays using an electron beam with 15 GeV energy, 1.5&pgr; mm-mrad normalized emittance, 3400 A peak current, and 280 fsec FWHM bunch duration. We find that this 65 &mgr;m rms diameter beam must overlap its radiation with a walkoff of no more than 5 &mgr;m for efficient gain. This places severe limitations on the magnetic field errors and other mechanical tolerances. The following is a discussion of the undulator design, specifications, alignment, engineering, and beam position monitoring we plan to implement for the LCLS X-ray FEL. ©1997 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.54589

出版商:AIP    

年代:1997

数据来源: AIP