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DXAS Beamline

The DXAS beamline is an experimental station dedicated to dispersive x-ray absorption spectroscopy (acronym for DXAS) techniques, in the hard x-ray energy range (5 to 14 keV). The peculiarity of this beamline is the capability to collect absorption spectra over an extended range of photon energies without any mechanical movement of its optical elements. The DXAS is especially suited for detecting weak signals in XANES (X-ray Absorption Near-Edge Spectroscopy) and XMCD (X-ray Magnetic Circular Dichroism) experiments and for tracking time-dependent evolution of chemical reactions.

DXAS is installed on a 1.67T bending-magnet source, and it was opened to users in 2005. The beamline is comprised by the synchrotron light source, a vertically focusing bendable mirror, a bent crystal polychromator, and an area detector. The beam path over the optical elements starts when it hits the bendable mirror, used for vertical focusing as well as harmonic rejection. Then the light beam impinges onto a polychromator bent crystal at several different incident angles, resulting in a polychromatic beam after reflection. The reflected beam is selected with a specific bandwidth of hundreds of eV, and is horizontally focused at the sample position. The transmitted signal, after the sample position, reaches an area detector. The photon energy–direction correlation is transformed into an energy–position correlation along the horizontal axis of the detector.

The main features of the beam line are fast acquisition and stability.  A whole X-ray absorption spectrum is acquired in a single detector shot. Thus, it makes the technique especially useful for the study of fast processes. Due to the absence of movement of the optical elements during the data acquisition, the focused beam at the sample position is inherently stable.

The beamline has been used to support studies in the fields of materials science, solution chemistry, heterogeneous and homogeneous catalysis, electrochemistry, magnetism and geosciences.

CONTACT & STAFF

For more information on this beamline, contact us.

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.

X-RAY ABSORPTION SPECTROSCOPY (XAS)

X-ray absorption spectroscopy (XAS) is a widely used technique for determining the local geometric on the atomic scale and/or electronic structure of matter. It provides information about a selected element in a material and is very effective for establishing structure-property relationships in any kind of materials.

Setup: Time-resolved XAS measurements in transmission mode

This setup is optimised for time-resolved measurements in transmission mode of homogeneous samples. The high penetration of hard X-rays allows working with a wide variety of sample environments (with gas, liquid, pressure…) in order to perform in situ and even operando time-resolved experiments that are crucial to better understand materials. Only transmission measurements are available on the DXAS beamline and the sample environment must fit within this restriction. Depending of the sample and sample environments, milliseconds time resolution is available.

X-RAY MAGNETIC CIRCULAR DICHROISM (XMCD)

X-ray magnetic circular dichroism (XMCD) technique is used to determine the element, orbital and spin magnetic properties of a material as a function of the environmental condition of the sample (temperature, pressure, applied field).

Setup: XMCD in transmission mode

This setup is optimised for transmission detection of XMCD signal, where the sample is between the pole pieces of a electromagnet with field up to 1 T and inside a cryostat allowing temperatures in the range of 20 to 300 K. High pressure anvil cell can also be employed for pressures up to 50 GPa.

Setup: XMCD in reflectivity mode

This setup is optimised for detection of the dichroic signal at the reflectivity of the x-rays from thin film samples, where the sample is between the pole pieces of an electromagnet with field up to 1 T.

LAYOUT & OPTICAL ELEMENTS

Element Type Position [m] Description
Source Bending magnet 0.00 Bending Magnet D06 exit A (4°), 1.67 T, 750 µm x 168 µm
Mirror Vertical focusing mirror 6.50 800 mm long Rh coated
Crystal Crystal polychromator 9.75 Water-cooled Si(111)

PARAMETERS

Parameter Value Condition
Energy range [keV] 5 – 14 Si(111)
Energy resolution [ΔE/E] 13.1 x 10-5 Si(111)
Energy band-pass [eV] Hundreds of eV
Beam size at sample [µm2, FWHM] 150 x 200 at 8 keV
Photon flux at sample [ph/s] 2 x 1011 at 8 keV

INSTRUMENTATION

Instrument Type Model Manufacturer Specifications
Detector Area detector Pylon2048F Princeton Instruments
Furnace Capillary, provide attachments to gas lines Max. temp.: 1000°C Max. heating ramp: 20°C/min Quartz capillary inner/outer diameters [mm]: 0.8/1.0; 1.0/1.2 and 2.0/2.4 LNLS in-house development
Furnace Tubular, provide attachments to gas lines Max. temp.: 1000°C Max. heating ramp: 20°C/min Pellet sample with a diameter of 13 or 6 mm LNLS in-house development
Mass flow controllers Gas flow [mL.min-1]: 0.2 – 750 BROOKS
Gas cylinders Pure gases: Ar, He, N2, synthetic air Gas mixture (% diluted in He): CO (20%), O2 (5 and 40%), H2 (5%), CO (5%), NO (5%), CH4 (20%), C3H8 (20%), C4H10 (30%), C2H4 (3%), C3H6 (5%), H2S (5%)
Thermoregulated bath TE2005 Down to -10°C and up to 80°C. Control accuracy of 0.1°C Tecnal
Mass spectrometer Gas analysis system OmniStar Tungsten (standard) filament. Mass range 1-100 amu. Gas flow rate 1-2 sccm. Qualitative and quantitative gas analysis Pfeiffer Vacuum
Liquid cell Optic path length [mm]: 0.3 – 7.5 LNLS in-house development
Potentiostats/Galvanostats N series 273A Autolab EG&G
Diffractometer 4 circle 424-511.1 For sample alignment (θ, 2θ, φ, χ) = 0.001° Huber
Electromagnetic coils Magnetic field Up to 1.5 T LNLS in-house development
Rotary permanent magnet Magnetic field Up to 0.9 T Magnetic Solutions
Voltage/Current power source BOP-GL 1KW 4 quadrant bipolar power supply. (0 to ± 50 Vdc) (0 to ± 20 Adc) Kepco
Picoammeter 6485 Keithley
Cryostats Down to 15 K and up to 420 K ARS
High-pressure cell High-pressure Diamond anvil cell Membrane and screw driven Up to 80 Gpa LNLS in-house development, Syntek, Princeton

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 the SOL group. MEDM (Motif Editor and Display Manager) and Python are used as a graphical interface to display and control the beamline devices.

HOW TO CITE THIS FACILITY

Users are required to acknowledge the use of LNLS facilities in any paper, conference presentation, thesis and any other published material that uses data obtained in the execution of their proposal.

 

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

CEZAR, J. C., SOUZA-NETO, N. M., PIAMONTEZE, C., TAMURA, E., GARCIA, F., CARVALHO, E. J., NEUESCHWANDER, R. T., RAMOS, A. Y., TOLENTINO, H. C. N., CANEIRO, A., MASSA, N. E., MARTINEZ-LOPE, M. J., ALONSO, J. A. & ITIE, J.-P.. Energy-dispersive X-ray absorption spectroscopy at LNLS: investigation on strongly correlated metal oxides. J. Synchrotron Rad. 17, 93-102 (2010). doi:10.1107/S0909049509041119.

An energy-dispersive X-ray absorption spectroscopy beamline mainly dedicated to X-ray magnetic circular dichroism (XMCD) and material science under extreme conditions has been implemented in a bending-magnet port at the Brazilian Synchrotron Light Laboratory. Here the beamline technical characteristics are described, including the most important aspects of the mechanics, optical elements and detection set-up. The beamline performance is then illustrated through two case studies on strongly correlated transition metal oxides: an XMCD insight into the modifications of the magnetic properties of Cr-doped manganites and the structural deformation in nickel perovskites under high applied pressure.

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 CNPEM library database. 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.


Medeiros, G. A. ; Corrêa, J.R.; Andrade, L. P.; Lopes, T. O. ; Oliveira, H. C. B. de; Diniz, A. B. ; Menezes, G. B. de; Rodrigues, M. O.; Neto, B.A.D.. A benzothiadiazole-quinoline hybrid sensor for specific bioimaging and surgery procedures in mice, Sensors and Actuators B-Chemical, v.328, p. 128998, 2021. DOI:10.1016/j.snb.2020.128998


García- Basabe, Y.; Gordo, V. O. ; Daminelli, L. M.; Mendoza, C. D.; Vicentin, F. C.; Matusalem, F.; Rocha, A. R.; Matos, C. J. S. de; Larrude, D. G.. Interfacial electronic coupling and band alignment of P3HT and exfoliated black phosphorous van der Waals heterojunctions, Applied Surface Science, v. 541, p.148455, 2021. DOI:10.1016/j.apsusc.2020.148455


Ramoni, M. ; Bassi, M. de J. ; Wouk, L. ; Pacheco, K. R. M. ; Fernández, A. B. ; Renzi, W.; Duarte, J. L. ; Rocco, M. L. M.; Roman, L. S.. Morphology, Photoexcitation Dynamics and Stability of Water-Dispersed Nanoparticle Films based on Semiconducting Copolymer, Thin Solid Films, v.721, p. 138536, 2021. DOI:10.1016/j.tsf.2021.138536


Sammaritano, M. L. A. ; Cometto, P. M. ; Bustos, D. A. ; Wannaz, E. D.. Monitoring of particulate matter (PM2.5 and PM10) in San Juan city, Argentina, using active samplers and the species Tillandsia capillaris, Environmental Science and Pollution Research, v.28, p.32962–32972, 2021. DOI:10.1007/s11356-021-13174-4


Rodrigues, L. do N. ; Scolfaro, D.; Conceição, L. da; Malachias, A.; Couto Jr., O. D. D.; Iikawa, F.; Deneke, C.. Rolled-Up Quantum Wells Composed of Nanolayered InGaAs/GaAs Heterostructures as Optical Materials for Quantum Information Technology, ACS Applied Nano Materials, v.4, n.3, p.3140-3147, 2021. DOI:10.1021/acsanm.1c00354


Soares, B. M.; Sodré, P. T.; Aguilar, A. M. ; Gerbelli, B. B. ; Pelin, J. N. B. D.; Arguello, K. B. ; Silva, E. R. da; Farias, M. A. de; Portugal, R. V.; Schmuck, C. ; Coutinho Neto, M. D.; Alves, W. A.. Structure optimization of lipopeptide assemblies for aldol reactions in an aqueous medium, Physical Chemistry Chemical Physics, v.23, n.18, p. 10953-10963, 2021. DOI:10.1039/d1cp01060c