View of the XPD beamline and of the workstation.

OVERVIEW

The XPD beamline is an experimental station dedicated to Powder X-ray Diffraction analysis and operates from 6 to 12 keV. However, the energy is set at 8keV (for maximum flux) and it is only changed to perform anomalous scattering experiments or to eliminate the effect of fluorescence for samples containing specific elements, such as Fe, Cu and Co. The beamline focuses on the structural studies of crystalline and nanocrystalline materials and it is able to perform both high resolution and faster in-situ experiments under non-ambient conditions.

XPD’s source is a 1.67T bending magnet, with a Huber 4+2 circle diffractomete, working in Bragg-Brentano geometry (theta-2theta) providing high quality powder diffraction data. Powder X-ray diffraction techniques largely benefit from the high-brilliance of synchrotron light sources in terms of photon flux, angular resolution, higher resolution, energy tunability as well as in situ studies in combination with fast detectors.

XPD is a beamline for studying the structure of all forms of polycrystalline materials, especially in a powder form. It offers the acquisition of powder patterns in high resolution mode, allowing the investigation of strain, lattice defects, and micro-structure of materials at ambient and cryogenic temperatures. In addition, powder diffraction using a synchrotron radiation X-rays source and fast detectors has become an essential technique for studying the change in crystalline or nanosized materials as a function of time under a variety of experimental conditions such as, temperatures ans gas. XPD allows kinetic experiments using a furnace installed onto the diffractometer, which allows gases to interact with the samples to simulate various reaction conditions or environments. A Mythen 1k linear detector can be used for fast data acquisition during in situ experiments. The beamline energy can be changed to perform anomalous scattering experiments, in which the contrast between scattering factors of different elements can be conveniently tuned. Energy tunability also eliminates the effects of fluorescence.

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.

AMBIENT MEASUREMENTS

Ambient measurements are conducted on samples which require the high resolution capability of the beamline. Here samples are measured under ambient temperatures and are exposed to the atmosphere during measurements. The setup gives accurate peak position and shape and reduces peak overlap of highly crystalline materials while reducing background signal. This set-up is normally required for quantitative analysis of samples, i. e. Structure determination of performing Rietveld Refinement to determine crystalline parameters, such as cell parameter and volume, crystal size, investigation of strain, lattice defects and micro-structure of materials. It is carried out at ambient conditions (room temperature) in Bragg-Brentano geometry or at cryogenic temperature with a cryostat. It is important to note that the cryostats work without sample spinning during the measurement. High resolution requires an analyzer crystal, a Ge (111) crystal, installed before the point detector (Cyberstar scintillation detector), which provides a step-size resolution of 0.002° in 2θ2θ. This analysis mode results in low photons flux and thus a lower intensity of the diffracted beam and consequently, longer data acquisition times (8-14 hours for each sample).

IN-SITU MEASUREMENTS

Canario Furnace

These measurements involve the use of a furnace with the additional capability of gas flow. With this setup various types of reactions can be simulated. The temperature range is dependent on the furnace used (please see types of furnaces available at the beamline). Various gas environments are allowed to simulate chemical reactions. Some restrictions are in place for safety as well as preventing damage to the furnaces. Thus, no corrosive gases are allowed. Further, restrictions apply to the use of hydrogen (5% max) and oxygen (20% max). We strongly urge you to contact the beamline staff prior to sending a beamtime proposal to certify that your experiment fits into our safety regulations. A mild vacuum may be applied to the furnace as well as humidity if required. A mass spectrometer is also available to analyze the chemical composition at the outlet of the furnace. The appropriate furnace will be selected by the beamline staff depending on the needs of the user.

The in-situ setup works for both fast measurements (lower resolution) using the Mythen 1K detector as well as the High resolution setup using the Cyberstar point detector. Please note the large time differences in collecting data between these two detectors. For further information about more complex setups, please contact the beamline staff.

CRYOSTAT

For low temperature measurements, a cryostat from Advanced research systems is available. The lowest temperature achievable is around 10 K. The measurement at low tempetature using cryostat can be carried out using fast detector Mythen or the Cyberstar point detector

SAMPLE PREPARATION

Sample holders from left to right: Furnace, cryostat, High-resolution

Depending on the type of experimental setup required samples may be prepared as either a powder or pellet. Powder samples are preferred however. Samples need to be ground down to the finest possible size to avoid sample related effects affecting the data. This applies to all data collections.

BEAMLINE ENERGY

XPD is normally fixed at 8 keV (λ=1.5498Å) which corresponds to the highest photon flux and is equivalent to Cu Kα wavelength used in conventional X-ray sources. However, the energy may be changed if anomalous diffraction experiment are required or if the sample is composed of Fe and/or Co. The energy is then set to 7 keV to avoid fluorescence. It is also possible to work at higher energies if it is important to increase the penetration depth of the X-rays into the sample, in the case of samples composed of high Z materials.

LAYOUT & OPTICAL ELEMENTS

Element	Type	Position [m]	Description
SRC	Bending Magnet	0.0	Bending Magnet D10 exit B (15°), 1.67 T,
FE	Front-end	-	-
S1	White Beam Slits	6.2	LNLS Slits (Cu and Ta)
M1	Cylindrical Vertical Collimating Mirror	7.3	Rh coated ULE, R = 1.7 to 21.7 km, $ \theta$ = 4.5 mrad
DCM	Double Crystal Monochromator	8.6	Water cooled Si (111)
S2	Monochromatic Beam Slits	20.0	LNLS Slits (Cu and Ta)
S3	Sample Slits	21.4	ADC Motorized Sample slits
ES	Experimental Station	21.9	4+2 circles Huber diffractometer

PARAMETERS

Parameter	Value	Condition
Critical Energy [keV]	2.08	-
Energy range [keV][Å]	4.5-15 (2.76-0.83)	Si (111)
Energy resolution [$ \Delta$E/E]	$ 2.5 \times 10^{-4}$	Si (111)
Beam size at sample [$ \rm mm^{2}$, FWHM]	3 x 2	at 8 keV
Beam divergence at sample [$ \rm mrad^{2}$, FWHM]	1 x 0.1	at 8 keV
Flux density at sample [ph/s/$ \rm mm^{2}$]	$ 2.5 \times 10^{10}$	at 8 keV

INSTRUMENTATION

Instrument	Type	Model	Specifications	Manufacturer
Detector	Linear	Mythen 1k	$ 50 \mu \rm m$ pixel, 1280 pixel, 2kHz frame rate	Dectris
Detector	Point Detector	Cyberstar X1000	$ \phi$ = 30 mm, Tl-doped NaI (NaI(Tl)), $ 10^6\, \rm counts.s^{-1}$	FMB Oxford
Detector	CCD Camera	X-ray eye	A-ray sensitive CCD	Photonic Science
Furnace	In-situ High Temperature Diffraction chamber	Arara	Max Temp.: 1000°C, Temp Rate: 10K/s, window port 210°	LNLS in-house development
Furnace	In-situ High Temperature Diffraction chamber	Canario	Max Temp.: 1000°C, Temp Rate: 10K/s, window port 210°	LNLS in-house development
Furnace	In-situ High Temperature Diffraction chamber	XRK900	Max Temp.: 900°C, Temp Rate: 20K/s	Anton Paar
Diffractometer	4+2 circles	5020	$ 2 \theta$ max=150°; $ \theta$ max=90°	Huber
Eurellian Cradle	2 circles	513	360° $ \Phi$; $\chi$ max=150°, min=-45°	Huber
Cryostats	He Closed Cycle Diffraction Cryostat	DE-202	Closed Cycle Cryo-cooler, Temperature range: <10 K – 350K, Window Ports: 5 - 90° Apart	ARS Cryo
Analyzer Crystal	Monochromatic Crystal	Ge(111)	$ 2 \theta$ step: 0.0025°	LNLS in-house development
Analyzer Crystal	Monochromatic Crystal	Si(111)	$ 2 \theta$ step: 0.0025°	LNLS in-house development
Analyzer Crystal	Monochromatic Crystal	HOPG(002)	$ 2\theta$ step: 0.05°	LNLS in-house development
Gas detector	Mass Spectrometer	QMA 100	-	Pfeiffer Vacuum
Gas detector	Mass Spectrometer	QMA 200	-	Pfeiffer Vacuum

CONTROL AND DATA ACQUISITION

The beamline is controlled using EPICS (Experimental Physics and Industrial Control System) that is running on a PXI from National Instruments. All data acquisition and diffractometer movements are done using fourc mode on SPEC (software for instrumentation control and data acquisition in X-ray diffraction experiments from Certified Science Software). For some graphical interfaces and beamline devices can be controlled using CSS (Control System Studio).

HOW TO CITE THIS FACILITY

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.

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.

XPD

Forbes, R. P.; Barrett, D. H.; Rodella, C. B.; Billing, D. G.. The thermoresponsive behaviour of Nasicon-like CuTi2(PO4)(3), Materials Characterization, v. 155, p. UNSP 109795, 2019. DOI: 10.1016/j.matchar.2019.109795

XPD

Ávila, Y. ; Plasencia, Y.; Osiry, H.; Martinez-DlCruz; Gonzalez, M.; Reguera, E.. Thermally Induced Spin Transition in a 2D Ferrous Nitroprusside, European Journal of Inorganic Chemistry, Early Access, 2019. DOI: 10.1002/ejic.201900837

DXAS PGM XDS XPD

Coutrim. L. T.; Rigitano, D. ; Macchiutti, C. ; Mori, T. J. A.; Lora-Serrano, R.; Granado, E.; Sadrollahi, E. ; Litterst, F. J.; Fontes, M. B. ; Baggio-Saitovich, E.; Bittar, E. M.; Bufaiçal, L.F. S.. Zero-field-cooled exchange bias effect in phase-segregated La2-xA(x)CoMnO(6-delta) (A = Ba,Ca,Sr; x=0, 0.5), Physical Review B, v. 100, n. 5, p. 054428, 2019. DOI: 10.1103/PhysRevB.100.054428

XPD

Toncon-Leal, C. F. ; Amaya-Roncancio, S. ; García-Blanco, A. A. ; Moreno, M. S.; Sapag, K.. Confined Iron Nanoparticles on Mesoporous Ordered Silica for Fischer-Tropsch Synthesis, Topics in Catalysis, v. 62, n. 12-16, p. 1086-1095, 2019. DOI: 10.1007/s11244-019-01201-1

XPD

Thyssen, V. V.; Assaf, E. M.; Sartore, D. M.. Effect of preparation method on the performance of Ni/MgO-SiO2 catalysts for glycerol steam reforming, Journal of the Energy Institute, v. 92, n. 4, p. 947-958, 2019. DOI: 10.1016/j.joei.2018.07.010

XPD

Ávila, Y. ; Osiry, H.; Plasencia, Y.; Torres, A. E. ; Gonzalez, M.; Lemus-Santana, A. A.; Reguera, E.. From 3D to 2D Transition Metal Nitroprussides by Selective Rupture of Axial Bonds, Chemistry-A European Journal, Early Access, 2019. DOI: 10.1002/chem.201902168

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