# OVERVIEW

BACK

The XAFS2 beamline is an experimental station dedicated to X-ray Absorption Spectroscopy in the hard x-rays energy range (3.5 to 17.0 keV). It focus on the study of the atomic-level structure as well as in the electronic and magnetic properties of matter, with applications in a wide range of scientific fields, such as atomic and molecular physics, chemistry, biology, environmental and geosciences and cultural heritage. Experimental techniques available include Fluorescence Spectroscopy, X-ray Excited Optical Luminescence, X-ray Reflectivity and Combined X-ray Absorption Fine Structure and X-Ray Diffraction.

The XAFS2 is a general-purpose X-ray absorption beamline. Since the completion of the commissioning works in 2007, a large number of users have been using this experimental facility in order to perform several kinds of experiments in different scientific areas. After approximately 7 years in operation this beamline has been substantially updated in order to improve its experimental possibilities. A 4-circle Huber diffractometer has been recently incorporated to perform combined experiments. This equipment collects XRD patterns with the XAFS.

Through the development of a new sample environment, it is now also possible to perform these measurements in situ/operando conditions. Other upgrades include a complete remodeling of the beamline software and its control system. The control system of the beamline has been renovated by the installation of a PXI. The PXI is from National Instruments (PXI-NI) and communicates with Galil/Parker controllers on an EPICS platform. Some parts of the motors were changed in order to improve performance with the upgrade and there were also important changes to the control hardware. The Windows operational system was replaced with Red Hat Linux and the 3-WinDCM control system with EPICS. Furthermore, a new python based script (Py4Syn) was added. This provides high-level abstraction for device manipulation, scan routines, real-time plots and more. This package was created with the aim of providing a simple yet powerful tool to allow scientists and users to develop their own scripts for data acquisition. For user-friendly interface builds a Control System Studio (CS-Studio) is used. The next step with the XAFS2 upgrade, namely, towards a high-throughput XAFS beamline, will involve testing the viability of performing QEXAFS.

# CONTACT & STAFF

Beamline Phone Number: +55 19 3512 1246
Beamline E-mail: xafs2@lnls.br

Coordinator: Gustavo de Medeiros Azevedo
Number: +55 19 3518 3192
E-mail: gustavo.azevedo@lnls.br

# EXPERIMENTAL TECHNIQUES

The following experimental techniques and setups are available to users in this beamline. To learn more about the techniques’ limitations and requirements (sample, environment, etc.) contact the beamline coordinator before submitting your proposal.

###### Conventional Transmission and Fluorescence XAS

X-ray absorption spectroscopy (XAS) is a widely used technique for determining the local geometric and/or electronic structure of matter. This setup is optimized for transmission and fluorescence XAS on “standard samples” in standard sample holders. The setup for these experiments has three ionization chambers, a multi-element solid state Ge fluorescence detector and a 5K cryostat. In general, the samples for these environments are membranes, pellets, thin films, liquid and bulk. More attention on sample homogeneity preparation must be given when in transmission mode.

Recent publications in this setup:

Sampaio DV, Souza NRS, Santos JCA, Silva DC, Fonseca EJS, Kucera C, Faugas B, Ballato J, Silva RS; Translucent and persistent luminescent SrAl2O4:Eu2+Dy3+ ceramics. CERAMICS INTERNATIONAL 42, 4306 (2016). doi:10.1016/j.ceramint.2015.11.108

Cappellari P.S., Buceta D., Morales G.M., Barbero C.A., Moreno M.S., Giovanetti L.J., Ramallo Lopez J.M., Requejo F.G., Craievich A.F., Planes G.A.. Synthesis of ultra-small cysteine-capped gold nanoparticles by pH switching of the Au(I)–cysteine polymer. JOURNAL OF COLLOID AND INTERFACE SCIENCE 441, 17 (2015). doi:10.1016/j.jcis.2014.11.016

###### In-situ XAS

This setup allow to submit the samples to different gas atmospheres, while heating up to 1000°C and work on transmission or fluorescence mode. There is a tubular furnace used in transmission and the samples are prepared as pellets. For in-situ fluorescence the sample are powder diluted in boron nitride inside a capillary. The optical table currently has three ionization chambers, a set of slits and motorized stages for user-supplied equipment. If you seek to use the in-situ setup you should contact us well in advance of any proposal deadline to establish technical feasibility.

Recent publications in this setup:

Coletta V.C.; Marcos F.C.F.; Nogueira F.G.E., Bernardi M.I.B; Michalowicz A.; Goncalves R.V.; Assaf, E.M.; Mastelaro V.R.. In situ study of copper reduction in SrTi1-xCuxO3 nanoparticles. PHYSICAL CHEMISTRY CHEMICAL PHYSICS 18, 2070 (2016). doi: 10.1039/C5CP05939A

Ribeiro R.U., Meira D.M., Oliveira D.C., Rodella C.B., Bueno J.M.C., Zanchet D. Probing the stability of Pt nanoparticles on encapsulated in sol-gel Al2O3 using in situ and ex situ characterization techniques. APPLIED CATALYSIS A-GENERAL 485, 108 (2014). doi:10.1016/j.apcata.2014.07.039

###### X-ray excited optical luminescence (XEOL)

This setup allows to get information about the optical behavior of a material when it irradiated with X-rays. It is possible to measure the emission spectra and/or the integrated luminescence as an energy function. Low temperature measurements (cryo-XEOL) are available using a cryostat, reaching 15K.  If you seek to use the XEOL setup you should contact us well in advance of any proposal deadline to establish technical feasibility.

Recent publications in this setup:

Hora DA, Andrade AB, Ferreira NS, Teixeira VC, Rezende, MVS (2016). X-ray excited optical luminescence of Eu-doped YAG nanophosphors produced via glucose sol–gel route. Ceramics International, 42(8), 10516-10519 (2016).
doi: 10.1016/j.ceramint.2016.03.142

Rezende M.V., Montes P.J.R., Andrade A.B., Macedo Z.S., Valerio M.E.G.. Mechanism of X-ray excited optical luminescence (XEOL) in Europium doped BaAl2O4 phosphor. Physical Chemistry Chemical Physics, 18, 17646-17654 (2016). doi: 10.1039/C6CP01183G

# LAYOUT & OPTICAL ELEMENTS

ElementTypePosition[m]Description
SourceBending Magnet0.0Bending Magnet D08 exit B (15°)
$1^{\rm st}$ cooled-slit systemTwo cooled UHV slit systems - vertically and horizontally - based on four independent mechanical feedthroughs, each one supporting at its ends a Ta blade mounted on a copper block.8.0Defines the lateral and vertical dimensions of the polychromatic beam impinging on the first mirror
$1^{\rm st}$ mirrorRh-coated cylindrical vertical collimating mirror with a ~3mrad grazing incidence angle9.2Collimate vertically the white radiation and sends a parallel synchrotron beam onto the two flat Si(111) Double Crystal Monochromator (DCM)
Double Crystal Monochromator (DCM)Flat Si(111) Double Crystal Monochromator10.5The DCM has fixed exit geometry and is the only optical element with thermal stabilization (i.e. water cooled).
$2^{\rm nd}$ slit systemTwo UHV slit systems - vertically and horizontally - based on four independent mechanical feedthroughs, each one supporting at its ends a Ta blade mounted on a copper block.11.6Without refrigeration, these slits are used to eliminate the spurious background radiation.
$2^{\rm nd}$ mirrorRh-coated toroidal bendable mirror12.8It refocuses vertically and horizontally the monochromatic beam of approximately $450 \mu \rm m$ in diameter at the sample position

# PARAMETERS

ParameterValueCondition
Energy range [keV]3.5 - 17.0Si(111)
Energy resolution [$\Delta$E/E]$1.7 \times 10^{-4}$at 7 keV
Beam size [$\mu \rm m^2$, FWHM]450 x 250at sample position
Flux density at sample [ph/s/$\rm mm^2$]$2.78 \times 10^{9}$ photons/s at 7 keV and 100mAMeasured with a photodiode 100% efficient
Harmonic Content< $3.94 \times 10^{-5}$at 7.5 keV

# INSTRUMENTATION

InstrumentTypeModelSpecificationsManufacturer
DetectorIon Chamber-Two electrodes in a distance of 14 mm. Length of 137 mm, 221 mm and 381 mm. A $25 \mu \rm m$ kapton window with a in/out area of 12 x 30 $\rm mm^2$LNLS in-house development
Detector15-element Germanium Solid State Detector (SSD)G-15 SSDHigh counting rate capability - 300.000cts/s. Si detector total active area - 750 $\rm mm^2$. Element sensitive thickness - 5 mm. $\rm N_2$ liquid cooled.Canberra
DetectorElectron Detector-Collector electrode (He medium) in an electric field produced by a 60V battery. The output is a signal amplification of about two orders of magnitudeLNLS in-house development
DetectorPhotomultiplierModel R928Side-on; V = -1200 V. It output is in current mode.Hamamatsu
DetectorSpectrometerUSB2000+covers the 200-1100 nm range and connects to light sources, optical fibers and other accessoriesOcean Optics
FurnaceTransmission/ FluorescenceCapilarMax Temp.: 900 C, Temp Rate: 10C/s. E5CK-T Ramp/Soak Process Controller-Omron. Sample holder for capillars (ID 0.8 mm/ OD 1mm) (ID 1 mm/ OD 1.2 mm) (ID 2 mm/ OD 2.2 mm)LNLS in-house development
FurnaceTransmissionTubularMax Temp.: 1100 C, Temp Rate: 10C/s. E5CK-T Ramp/Soak Process Controller-Omron. Sample holders of 8 mm and 4 mm diametersLNLS in-house development
Diffractometer4-circle424-511.1Resolution ($\theta$, $2\theta$, $\phi$, $\chi$) = 0.001°Huber
Mass spectrometerGas Analysis SystemOmniStar QMS 200Tungsten (standard) filament. Mass range 1-100 amu. Gas flow rate 1-2 sccm. Qualitative and quantitative gas analysis.Pfeiffer Vacuum
CryostatCryogen free and top loading sample in helium, fast sample change.Omniplex: CS204*F-FMX-19OPHigh cooling power and fast cooldown. 4 K cold head (0.2 W at 4.2 K). 180° Kapton window for x-ray fluorescence detection modeARS
Cryostat for cryo-XEOLCooling power He closed cycle cryocoolerDE-202 Cryocooler series$T_min = 15 K$

# CONTROL AND DATA ACQUISITION

All beamline controls are done through EPICS (Experimental Physics and Industrial Control System), running on a PXI from National Instruments. The data acquisition is done using a Red Hat workstation with the Py4Syn, developed at LNLS by SOL group. CSS (Control System Studio) is used as a graphical interface to display and control the beamline devices.

The beamline can be operated remotely by using LabWeb for experiments in conventional transmission (without furnaces and gases). We are working to improve these possibilities on Sirius. For more details, contact the beamline coordinator.

# APPLYING FOR BEAMTIME

Submission calls are usually announced twice per year, one for each semester. All the academic research proposals must be submitted electronically through the SAU Online portal. Learn more about how to submit a proposal here.

# HOW TO CITE THIS BEAMLINE

Users are required to acknowledge the use of LNLS facilities in any publications and to inform the Laboratory about any publications, thesis and other published materials. Users must also cooperate by supplying this information upon request.

Support text for acknowledgements:

This research used resources of the Brazilian Synchrotron Light Laboratory (LNLS), an open national facility operated by the Brazilian Centre for Research in Energy and Materials (CNPEM) for the Brazilian Ministry for Science, Technology, Innovations and Communications (MCTIC). The _ _ _ beamline staff is acknowledged for the assistance during the experiments.

Additionally, in publications related to this facility, please cite the following publication.

FIGUEROA, S. J. A.; MAURICIO, J. C.; MURARI, J.; BENIZ, D. B.; PITON, J. R.; SLEPICKA, H. H.; FALCÃO DE SOUSA, M.; ESPÍNDOLA, A. M.; LEVINSKY, A. P. S.. Journal of Physics: Conference Series 712 (2016) 012022. DOI: 10.1088/1742-6596/712/1/012022

The XAFS2 is a general-purpose X-ray absorption beamline. It is the second one built at the LNLS. After approximately 7 years in operation this beamline has been substantially updated in order to improve its experimental possibilities. Recently arrived, a 4-circle Huber diffractometer has been incorporated to perform combined experiments. This collects XRD patterns with the XAFS. Through the development of a new sampling environment it is now also possible to perform these measurements in situ/operando conditions. Other upgrades include a complete remodelling of the beamline software and its control system. The following new systems are crucial for the next steps that are currently underway at the beamline, namely, (i) enabling remote access for users and (ii) the testing of QEXAFS measurements.

# PUBLICATIONS

Scientific publications produced with data obtained at the facilities of this beamline, and published in journals indexed by the Web of Science, are listed below.

Attention Users: Given the importance of the previous scientific results to the overall proposal evaluation process, users are strongly advised to check and update their publication record both at the SAU Online website and at the For the library, updates can be made by sending the full bibliographic data to the CNPEM library (biblioteca@cnpem.br). Publications are included in the database after being checked by the CNPEM librarians and the beamline coordinators.

MORE PUBLICATIONS

XAFS2

Teixeira, V. C.; Andrade, A. B.; Ferreira, N. S.; Galante, D.; Rodrigues, L. C. V.; Rezende, M. V. dos S.. X-ray excited optical luminescence and morphological studies of Eu-doped LiAl5O8, PHYSICA B-CONDENSED MATTER, v. 559, p. 62-65, 2019. DOI: 10.1016/j.physb.2019.01.050

XAFS2

Fonseca, J.; Bion, N.; Licea, Y. E.; Morais, C. M. ; Rangel, M. C. do; Dupres, D. ; Epron, F.. Unexpected redox behaviour of large surface alumina containing highly dispersed ceria nanoclusters, Nanoscale, v. 11, n. 3, p. 1273-1285, 2019. DOI: 10.1039/c8nr07898j

XAFS1   XAFS2

Arruda, E. G. R. de; Rocha, B. A. ; Barrionuevo, M. V. F. ; Aoalssteinsson, H. M. ; Galdino, F. E.; Loh, W.; Lima, F. A.; Abbehausen, C.. The influence of Zn-II coordination sphere and chemical structure over the reactivity of metallo-beta-lactamase model compounds, Dalton Transactions, v. 48, n. 9, p. 2900-2916, 2019. DOI: 10.1039/c8dt03905d

XAFS2

Nieva, N. E. ; Bia, G.; Garcia, M. G.; Borgnino, L.. Synchrotron XAS study on the As transformations during the weathering of sulfide-rich mine wastes, Science of the Total Environment, v. 669p. 798-811, 2019. DOI: 10.1016/j.scitotenv.2019.03.160

XAFS2

Castells, M. P. L. ; Hauser, A. W. ; Ramallo-López, J. M.; Buceta, D.; Giovanetti, L. J.; López-Quintela, M. A.; Requejo, F. G.. Increasing the optical response of TiO2 and extending it into the visible region through surface activation with highly stable Cu-5 clusters, Journal of Materials Chemistry A, v. 7, n. 13, p. 7489-7500, 2019. DOI: 10.1039/c9ta00994a

XAFS2

Teles, C. A.; Souza, P. M. de; Braga, A. H.; Rabelo Neto, R. C.; Teran, A. ; Jacobs, G.; Resasco, D. E.; Noronha, F. B.. The role of defect sites and oxophilicity of the support on the phenol hydrodeoxygenation reaction, Applied Catalysis B-Environmental, v. 249,p. 292-305, 2019. DOI: 10.1016/j.apcatb.2019.02.077

MORE PUBLICATIONS