National Synchrotron Light Laboratory Research Articles

Angle-dispersive diffraction with synchrotron radiation at Laboratório Nacional de Luz Sı́ncrotron (Brazil): potential for use in biomedical imaging

At low angles the scattering of X-rays in the diagnostic energy range (low-momentum transfer), it is probable that the scattering interaction will be coherent. This coherence gives rise to interference effects resulting in X-ray diffraction patterns that are characteristic of the scattering material. The usefulness of coherent scattering is not limited to crystallography. It can provide information about biological material as well. The interatomic and intermolecular co-operative effects which modify the free-atom coherent scattering process are well known for highly ordered structures such as crystalline materials but are important for amorphous solids and liquids where short-range ordering occurs. X-ray diffraction using synchrotron radiation has became a well established technique. This work introduces a non-destructive synchrotron radiation X-ray diffraction imaging technique. The feasibility of the X-ray diffraction computed microtomography using synchrotron radiation has been investigated. This research was carried out at the X-ray diffraction beam line of the National Synchrotron Light Laboratory supported by the National Council for Scientific and Technological Development (LNLS/CNPq) in Brazil. These experimental patterns were carried out with a 500 μm slit in front of the detector and an 11.101 keV beam ( λ=1.117 Å) monochromatic beam from the double crystal monochromator. The diffracted beam was detected by a fast scintillation detector (10 6 counts s −1) designed specifically to meet the needs of high quality X-ray diffraction and synchrotron radiation experiments. The data were recorded at rates of one second per degree of 2 θ (angular steps equal to 0.05±0.01°) and registered by a multichannel analyzer. These experimental data could be used to evaluate the scattering properties of different tissue-substitute (water, lucite, nylon, plastic and polystyrene) and bone-substitute (hydroxyapatite and aluminum) materials. The data are in good agreement with those obtained by other authors, indicating the feasibility of the imaging technique.

Acoustically adjustable LiNbO3 double-crystal monochromator for synchrotron radiation

First experiments with the acoustically controlled LiNbO3 double-crystal monochromator for synchrotron radiation have been performed on the diffraction beamline of the Brazilian National Synchrotron Light Laboratory. In order to modify x-ray optical properties of LiNbO3 crystals, 290 MHz surface acoustic waves were generated with the aid of interdigital transducers, fabricated on the polished crystal surfaces by using microelectronics technology. It was shown that by the appropriate choice of diffraction planes, the LiNbO3 double-crystal monochromator can be used for both high-flux and high-resolution applications. Surface acoustic waves allow adjustment of an angular width of diffraction profile to a divergence of the incident synchrotron radiation, optimizing matching conditions for x rays of different wavelengths. Diffraction measurements under surface acoustic wave excitation demonstrated that the parameters of the x-ray beam issuing from the monochromatization system are indeed acoustically controlled, providing a 2–2.5-fold broadening of the diffraction profile and a 1.5-fold gain in the maximum diffraction intensity.

Double-crystal diffractive modulator of synchrotron radiation

The efficiency of time-modulation of synchrotron radiation by a double-crystal monochromator periodically curved by pulsed surface acoustic waves has been studied both experimentally and theoretically. It has been shown that the efficiency of such a system is significantly higher as compared to x-ray modulation by surface acoustic waves applied to x-ray mirrors—that is under the conditions of total external reflection. Possible modifications and improvement of a synchrotron radiation double-crystal diffractive modulator are discussed. The experiments were done at the diffraction beamline at the Brazilian National Synchrotron Light Laboratory (LNLS).

The Decision-Making Process in the Construction of the Synchrotron Light National Laboratory in Brazil

In 1981, a small group of Brazilian physicists started a very effective campaign to construct a national synchrotron radiation laboratory. By the end of 1984, the project was officially approved and, surviving political shifts brought about by the end of military rule, construction of the lab began in 1987. Why, in these times of declining budgets in world science, should a relatively poor country, struggling with financial difficulties, decide to invest millions of dollars in a Big Science facility? We examine the decision-making process leading to the lab's construction, focusing on three intermediate stages: the decision to build the lab; the choice of its site; and the size of the machine. We show that basic support came much more from policymakers than from scientists and potential users, and that the political ability of the few scientists directly involved with the project was crucial for its implementation. We conclude that the decision to build was made, not to answer scientific problems or to achieve new technological applications relevant to Brazil, but mainly to stimulate technological development, and to introduce the country to the new level of scientific organization represented by Big Science and National Laboratories.

The protein crystallography beamline at LNLS, the Brazilian National Synchrotron Light Source

The Brazilian National Synchrotron Light Laboratory - LNLS, will have a dedicated protein crystallography beamline. The beamline under construction includes cylindrical mirror and bent crystal monochromator focusing the high flux of synchrotron radiation in the horizontal plane at the position of the sample. The monochromatic radiation will be tuneable between 2.0 and 1.0 Å with the optimum wavelength at 1.3–1.6 Å, chosen with the aim of maximizing the photon flux from the bending magnets of the storage ring (1.37 GeV). Diffraction images will be recorded on a commercial image plate detector system with on-line readout. The beamline set-up will include cooler/chiller for the samples and biochemical lab for crystallization, heavy-metal soaks, crystal storage and mounting at 22°C and 4°C, will also be available. The facility, intended to serve the national and international community, is planned to be brought into operation in the second half of 1997. It is foreseen that the commissioning of the first protein crystallography beamline in Latin America will boost the number of protein structures determined locally and will increase the general interest of the molecular biology and biochemical research community of Brazil in this area.

Set-up and Experimental Parameters of the Protein Crystallography Beamline at the Brazilian National Synchrotron Laboratory

The Brazilian National Synchrotron Light Laboratory (LNLS) has a dedicated protein crystallography beamline. The optical elements of the beamline include an elastically bent cylindrical mirror and a triangular bent-crystal monochromator, which focus synchrotron radiation at the position of the sample in the vertical and horizontal planes, respectively. The monochromatic radiation is tunable between 2.0 and 1.2 A with the optimum wavelengths from 1.3 to 1.6 A, chosen to maximize the photon flux from the bending magnets of the storage ring (1.37 GeV). Diffraction images are recorded on a 345 mm-diameter MarResearch image-plate detector system with on-line readout. The experimental parameters of the beamline, such as the integral monochromatic flux and focus size, have been measured. The size of the beam at the position of the focal point is 0.5 x 0.5 mm(2). The flux density is between 4.4 x 10(10) and 8 x 10(10) photons s(-1) mm(-2) for wavelengths from 1.28 to 1.6 A. The energy resolution is sufficient to measure absorption edges of elements between 1.28 and 2 A. The facility, intended to serve the national and international community, has been commissioned and is available for users.

A user-extensible graphical user interface for control of either instrument-control program, ACE or spec

A single Graphical User Interface (GUI) has been developed to control the ACE [1–3] and spec [4] beamline-control and data-acquisition programs in use at Brookhaven National Laboratory's National Synchrotron Light Source (NSLS). The basic GUI provides a user-friendly interface to the primitive and macro-controlled operations of the programs. In addition, the GUI package provides facilities to allow users of the program to extend the GUI by construction of their own GUI screens so that they may have user-friendly interfaces to their customized macros. The GUI is easy to install and the authors expect to maintain it.