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Sapucaia Beamline

SAPUCAIA will be a beamline dedicated to small-angle X-ray scattering technique (SAXS). SAXS is a structural characterization technique used to study the morphological (shape, size and spatial organization) and dynamical properties of nano- and micro-structured objects. It is a well-established technique, having application in a wide variety of research fields such as in physics, chemistry, biology, engineering and industry. The beamline will permit to answer many questions concerning life science (biological and medical applications), structural biology (proteins, nucleic acids, lipids and general macromolecules) and in a vast field of material science, including nanotechnology, polymers, rheology and environment sciences.

SAPUCAIA beamline was idealized and designed to have a high performance (with high reproducibility of the experiments), in addition to its easy use and change of the experimental setup whenever the user wishes. It will host a tunnel of about 15 m long and 2 m of diameter. Inside the tunnel (always kept under low pressure) there will be a support containing the detection system. The system can move along rails, allowing the users to have access to different experimental conditions while carrying out their experiments. The definition of the beamline design was based on three main characteristics that make SAPUCAIA one of the most important beamlines worldwide, which are: (i) low parasitic scattering, (ii) low beam divergence and (iii) high stability of the optical components.

Low parasitic scattering:

An important fraction of high-impact scientific cases that use the SAXS technique come from biological areas. Several of these cases involve monitoring changes in the structure of proteins or other biological (macro)molecules induced by changes in the environment (such as pH change, presence of ions), or due to the presence of other molecules. These small changes, which can hide a huge range of information about the systems, can be extremely subtle or almost imperceptible for most structural characterization techniques. Thus, the SAPUCAIA beamline was designed so there are no vacuum windows through the optical beam path. The main advantage of this feature is the ability to obtain structural information in regions of the scattering pattern which are generally overshadowed by the beamline background, allowing to observe details in the scattering pattern that would be indistinguishable in experiments performed on beamlines that use vacuum windows to protect their optical components.

Low beam divergence:

SAPUCAIA beamline is planned to be mounted in a high beta straight section of SIRIUS accelerator. High beta sections are not so popular for SAXS beamlines since in these regions of the accelerator the electron packages have the largest horizontal and vertical sizes of the source, implying that the focus sizes inside the beamline are considerably larger compared to a low beta section. However, a great advantage of this configuration is the possibility to obtain beams with considerably smaller intrinsic divergence. This brings several advantages to the SAXS technique, since the low divergence allows it to reach even lower scattering angles. SAPUCAIA beamline is designed to provide information up to 4 micrometers in size.

High stability:

Another great advantage of building the beamline in a high beta straight section is its optical stability. As the beam is relatively small in all the beamline extension, it is not necessary to change the optics (mainly on the mirrors orientation and positions) to optimize some experimental condition. This feature brings benefits such as: (i) changing the position of the detector becomes quick and reproducible; (ii) The beamline optics becomes extremely stable, since the optical elements do not need to be moved; and (iii) experiments on different days will be performed with the same optical configuration – which permits an excellent repeatability and reliability of the experiments.

CONTACT & STAFF

Facility E-mail: sapucaia@lnls.br

Coordination: Leandro R. S. Barbosa
Tel.:
E-mail: leandro.barbosa@lnls.br

Click here  for more information on this Facility team.

EXPERIMENTAL TECHNIQUES

SAPUCAIA beamline will cover a range in the reciprocal space from 0.0014 to about 32 nm-1 (covering sizes on the order of few Angstroms to about 4 μm), depending on the beam energy and sample-to-detector distance.

In the SAPUCAIA beamline, it will also be possible to perform Time-Resolved SAXS measurements. That is, thanks to the high photon flux and the detection system, we will be able to perform measurements in the millisecond time-scales, allowing the characterization of dynamical properties of biological and material science systems. This opens the possibility of in-situ experiments on biological systems – such as monitoring chemical reactions and conformational evolutions of macromolecular systems.

The beamline will be equipped with a liquid sample-changer robot that will reduce the time of the experiments and data collection by up to 70%. This setup will allow experiments in liquid samples changing their temperature and will allow the handling of samples composed of only a few dozens of microliters, benefiting about 75% of the LNLS SAXS user community.

For the user community that works with solid samples, the beamline will work with a mail-in system where users with approved proposals will be able to assemble a sample grid and send them to LNLS for remote experiments, in a simple and fast way.

Together with SAXS technique, some experiments require the measurement of the scattering intensity spread at higher angles. This technique, known as wide-angle X-ray scattering (WAXS) can also be measured in SAPUCAIA beamline concurrently with SAXS technique, allowing to obtain information also on the molecular conformation of the studied structures.

The beamline is also prepared to receive specific equipment for experiments (brought by users or developed together with the beamline staff) which will allow the study of specific problems of each scientific group.

LAYOUT & OPTICAL ELEMENTS

Elements Type Position [m] Description
SOURCE Undulator 0 2x 1.122 m long KYMA undulators, horizontal polarization, high beta straight section
S1 White slit 26 Slit placed on the optical hutch entrance
DCM Monochromator 29 Two-crystals vertical-bounced monochromator (Si 111 or Si 311)
M1 Mirror 31 Horizontal-bounced Rh toroidal mirror (Meridional radius: 97 mm; Sagittal radius: 7800 m)
S2 Defining slits 32 Beam defined slits
S3 Sample slits 47.5 Scatterless slits placed in front of sample position
SH Sample-holder 47.8 Sample-holder position
TN Tunnel 48 – 62 Vacuum tunnel with detector wagon
DET Detector 48.5 – 58.5 In-house developed PiMega Detector

PARAMETERS

Parameter Value Condition
Energy range (keV) 6 – 17 Optimized to work using 10 keV
Beam size (μm2) 250 x 220  (h x v) On sample position. Estimative based on simulations (Shadow)
Beam divergence (μrad2) 21 x 19 (fonte, h x v)
29 x 23 (amostra, h x v)
Estimative based on simulations (Shadow)
Photon flux
(photons/s/100mA)
1.5 x 1013 (@6 keV)
0.5 x 1013 (@10 keV)
0.1 x 1013 (@17 keV)
On sample position. Estimative based on simulations (Shadow)
Energy Resolution (λ/Δλ) 30000 (Si 311)
7500 (Si 111)
Estimative for 10 keV based on optical parameters and beamline divergence
Polarization Horizontal KYMA Undulators
Q min – max (nm-1) 0.018 – 5.8 (@6 keV)
0.030 – 9.7 (@10 keV)
0.052 – 16.5 (@17 keV)
Detector close to sample (0.8 m)
Q min – max (nm-1) 0.0014 – 0.45 (@6 keV)
0.0023 – 0.75 (@10 keV)
0.0040 – 1.3 (@17 keV)
Detector far from sample (10.8 m)
Q max (WAXS) (nm-1) 11.2 (@6 keV)
18.4 (@10 keV)
31.2 (@17 keV)
Detector inside tunnel, 0.8 m from sample