The National Synchrotron Light Source II (NSLS-II), a Department of Energy (DOE) Office of Science User Facility located at Brookhaven National Laboratory, offers an advanced suite of beamlines ded...

We have developed a powerful and readily accessible suite of structural biology tools for the lifescience research community.With the main focus on macromolecular crystallography (MX) and xray scattering, there is also a user program in fluorescence imaging of metals in biological materials.

We report on the status of the development of three beamlines for the National Synchrotron Light Source-II (NSLS-II), two for macromolecular crystallography (MX), and one for wide- and small-angle x-ray scattering (SAXS). Funded by the National Institutes of Health, this suite of Advanced Beamlines for Biological Investigations with X-rays (ABBIX) is scheduled to begin operation by 2015. The two MX beamlines share a sector with identical canted in-vacuum undulators (IVU21). The microfocusing FMX beamline on the inboard branch employs a two-stage horizontal source demagnification scheme, will cover an energy range of 5 – 23 keV, and at 12.7 keV will focus a flux of up to 1013 ph/s into a spot of 1 μm width. The companion AMX beamline on the short outboard branch of the sector is tunable in the range of 5 – 18 keV and has a native focus of 4 μm (h) × 2 μm (v). This robust beamline will be highly automated, have high throughput capabilities, and with larger beams and low divergence will be well suited for structure determinations on large complexes. The high brightness SAXS beamline, LIX, will provide multiple dynamic and static experimental systems to support scientific programs in solution scattering, membrane structure determination, and tissue imaging. It will occupy a different sector, equipped with a single in-vacuum undulator (IVU23). It can produce beams as small as 1 μm across, and with a broad energy range of 2.1 – 18 keV it will support anomalous SAXS.

Two transmission-mode diamond X-ray beam position monitors installed at National Synchrotron Light Source (NSLS) beamline X25 are described. Each diamond beam position monitor is constructed around two horizontally tiled electronic-grade (p.p.b. nitrogen impurity) single-crystal (001) CVD synthetic diamonds. The position, angle and flux of the white X-ray beam can be monitored in real time with a position resolution of 500 nm in the horizontal direction and 100 nm in the vertical direction for a 3 mm × 1 mm beam. The first diamond beam position monitor has been in operation in the white beam for more than one year without any observable degradation in performance. The installation of a second, more compact, diamond beam position monitor followed about six months later, adding the ability to measure the angular trajectory of the photon beam.

We present the first resonant x-ray reflectivity measurements from a liquid surface. The surface structure of the liquid Hg-Au alloy system just beyond the solubility limit of 0.14at% Au in Hg had previously been shown to exhibit a unique surface phase characterized by a low-density surface region with a complicated temperature dependence. In this paper we present reflectivity measurements near the Au LIII edge, for 0.2at% Au in Hg at room temperature. The data are consistent with a concentration of Au in the surface region that can be no larger than about 30at%. These results rule out previous suggestions that pure Au layers segregate at the alloy surface.

When high-brilliance radiation is needed for experiments, insertion device sources are generally viewed on-axis. Off-axis emission of flux can be prodigious especially from wiggler sources having large emission fans. The on-axis and off-axis radiation emission characteristics from insertion device sources have been calculated extensively and are well known, but experimental verifications of some characteristics, particularly those associated with off-axis emission, are relatively few. Here measurements of the flux spectrum and apparent source size are described, as a function of horizontal emission angle, from the former X25 hybrid wiggler at the National Synchrotron Light Source (NSLS).

It has been proposed that free electron laser radiation can be used for ultrafast time-resolved x-ray diffraction experiments based on the NIR pulse / FEL probe scheme.We developed a multipurpose vacuum chamber which function is to be used in the pump / probe diffraction experiments with free electron laser (FEL) radiation.By exciting with optical laser pulses in the near infrared regime (800 nm) it is possible to investigate in silver behenate (AgBh) an optical excitation dependent intensity modulation of its Bragg reflection.The time-resolution of the experiment was about 150 fs.It is assumed that in AgBh the optical laser pulses introduce a structural strain and disorder phase which can be monitored by the intensity modulation of the AgBh Bragg reflection.The strain / disorder results from an ultrafast temperature jump in the system through the non-resonant excitation at 800 nm.Our studies on model systems like silver behenate has answered the questions of whether it is possible to use soft x-ray free electron laser radiation for studying chemical systems of periodic order and whether it is possible to utilize the time structure of soft x-ray free electron laser radiation for studying the structural dynamics of chemical systems of periodic order, opening a window for the structural studies on nanoperiodic systems [1], [2].Time dependent changes of the Bragg diffraction peak intensities (photo-excited AgBh nanotubes) A) Intensity difference maps for various time points B) Time evolution of the integral intensity changes of the Bragg reflection.The creation of the photo-disordered phase and its modelbased on its kinetic analysis are shown in the inset

We describe a concept for X-ray optics to feed a pair of macromolecular crystallography (MX) beamlines, which view canted undulator radiation sources in the same storage ring straight section. It can be deployed at NSLS-II and at other low-emittance third-generation synchrotron radiation sources where canted undulators are permitted, and makes the most of these sources and beamline floor space, even when the horizontal angle between the two canted undulator emissions is as little as 1–2 mrad. The concept adopts the beam-separation principles employed at the 23-ID (GM/CA-CAT) beamlines at the Advanced Photon Source (APS), wherein tandem horizontally deflecting mirrors separate one undulator beam from the other, following monochromatization by a double-crystal monochromator. The scheme described here would, in contrast, deliver the two tunable monochromatic undulator beams to separate endstations that address rather different and somewhat complementary purposes, with further beam conditioning imposed as required. A downstream micro-focusing beamline would employ dual-stage focusing for work at the micron scale and, unique to this design, switch to single-stage focusing for larger beams. On the other hand, the upstream, more highly automated beamline would only employ single-stage focusing.

General optimization procedure, computation methods used, and the obtained optimal parameters of undulators for the NSLS-II project beamlines are reported. The optimization starts with high-accuracy calculation of undulator magnetic fields, using Radia magnetostatics code, for a large set of periods and vertical gaps of a given undulator type, given magnetic materials and a scalable magnet geometry. From the resulting magnetic fields, a sub-set of undulator periods and the corresponding vertical gaps, providing the required low-energy cut-off values of spectral harmonics for each particular beamline, is determined. In parallel, from the same Radia undulator models, angular magnetic kick maps are calculated, and the insertion device effect on electron beam is simulated using Tracy-2 tracking code based on symplectie integrator. After these simulations, magnet parameters are fine-tuned and the maximal acceptable undulator lengths are determined for different straight sections, as functions of minimal gap and with due regard for the electron beam vertical "stay clear" constraint in the case of in-vacuum undulators. Finally, the optimal undulator period and length are determined as the values providing maximal spectral flux among the pre-selected undulator cases, already satisfying the requirements concerning the harmonic cut-off values and the effect on electron beam.

During January 2006, a new hybrid PM-type in-vacuum mini-gap undulator (MGU) with NdFeB magnets and vanadium permendur poles was installed within the X25 straight-section of the 2.8GeV National Synchrotron Light Source (NSLS) electron storage ring. This new insertion device was implemented to deliver high brightness X-ray beams within the energy range of ∼5.5–20keV for monochromatic single-crystal X-ray macromolecular crystallography. The spectral output from such a device is very sensitive to the storage ring machine parameters and in this paper, we report the precise determination of the new X25 MGU performance by implementing a single-crystal silicon (111) X-ray spectrometer to measure the X-ray energy-dependent flux throughput and infer the corresponding brightness values for a wide range of undulator gap openings. We compare these values to synchrotron radiation calculations using the SPECTRA (version 8.0) code and confirm both the integrity of the new X25 MGU device and the emittance values of the NSLS electron storage ring.

The National Synchrotron Light Source (NSLS) 2.8 GeV electron storage ring continues to set high standards in insertion-device research and development. The Chasman-Green NSLS lattice design provides for dispersion-free long straight sections in addition to a very small vertical beta function. As the electron beam size is proportional to the square root of this function, a program to exploit this feature was undertaken more than a decade ago by implementing short-period small-gap insertion devices in the NSLS storage ring. The possibility of utilizing existing moderate-energy synchrotron radiation electron storage rings to produce high-brightness photon beams into the harder X-ray region have been realised using in-vacuum undulators. In this article the operation of a 1.25 cm-period mini-gap undulator, operating down to a gap of 3.3 mm within the NSLS X13 straight section, is reported. It is the brightest source of hard X-rays in the energy range approximately 3.7-16 keV at the NSLS, and replaces an in-vacuum undulator which had a more limited tunability.

An in-vacuum short-period mini-gap undulator (MGU) has recently been installed within the National Synchrotron Light Source (NSLS) X13 straight-section. The MGU is a hybrid design, consisting of NdFeB permanent magnets and vanadium permendur poles. The MGU period is 1.25 cm, the overall length is 35 cm, and the gap can be varied between 3.3 and 11 mm. The higher magnetic field provided by the hybrid design supercedes that of the previous X13 undulator device (IVUN), allowing for a greater tunability. Operating down to a magnetic gap of 3.3 mm, the on-axis magnetic field is 0.92 Tesla, corresponding to a deflection parameter Ksimilar to1.07. The performance of the MGU has been measured using a single crystal spectrometer. At a gap of 3.3 mm, the MGU's fundamental energy was recorded at 3.7 keV with a brightness of 4 x 10(17) ph/sec/mm(2) /mrad(2)/0.1%BW/300mA.

We have measured the site-specific valence electronic structure of alpha-Fe2O3 by using a spatially modulated x-ray standing wave as the excitation source for photoemission. Contributions to the valence-band density of states from oxygen and iron ions are separated by this method. Both a bonding and nonbonding state originating from oxygen ions are obtained. The valence densities of states from iron agree well with predictions based on configuration-interaction cluster calculations by Fujimori [Phys. Rev. B 34, 1318 (1986)] which considered charge transfer from ligand to metal. The effects of strong hybridization between Fe and O valence states to x-ray emission and resonance photoemission are also evident.

An empirical evaluation of data obtained using parallel beam geometry powder diffraction from laboratory sources is presented based on signal to noise ratios, count times, and Rietveld refinement of data from NIST standards.Two distinct geometries were used, Debye-Scherrer and reflection, as well as point detectors and a linear position-sensitive detector.The diffraction geometries used include: 1. Parabolic multilayer optic coupled into an asymmetric Si (220) channel-cut two-bounce crystal with a similar crystal on the receiving side.2. Parabolic multilayer optic on the incident beam side and soller collimator on the receiving side.3. Parabolic multilayer optic on the incident beam side and flat multilayer optic on the receiving side.4. Parabolic multilayer optic on the incident side with a linear position-sensitive detector on the receiving side.With respect to conventional Bragg-Brentano geometry, the parallel beam systems provide accurate lattice parameters and highly reliable peak locations.The peak widths as a function of angle can be modeled using Cagliotti parameters and show no significant problems.However, it is apparent from Rietveld refinement that the systems that incorporate multilayer optics without crystal optics provide data that is slightly different than that obtained using parafocusing systems.In particular, the peak tails and location of the α two components are not correctly modeled when using traditional approaches.

Silicon crystals at room temperature employed as x-ray monochromators on synchrotron radiation beamlines, when subjected to high-power-density loading, suffer thermal distortions which compromise their x-ray diffraction efficiency and result in a reduction of the inherent brilliance of the synchrotron beam. At cryogenic temperatures however (below 150 K), silicon crystals suffer little or no thermal distortions under high-power-density loading. The design and implementation of a channel-cut silicon crystal monochromator which is cooled to as low as 50 K, using a commercial helium refrigerator and circulation system and a custom-designed heat exchanger for the monochromator crystal, are described. Test results have been obtained on the National Synchrotron Light Source X13B in-vacuum undulator beamline as well as the higher power X25 wiggler beamline.

We have determined the Ti and O components of the rutile TiO2 valence band using the method of site-specific x-ray photoelectron spectroscopy. Comparisons with calculations based on pseudopotentials within the local density approximation reveal the hybridization of the Ti 3d, 4s, and 4p states, and the O 2s and 2p states on each site. These chemical effects are observed due to the large differences between the angular-momentum dependent matrix elements of the photoelectron process.