Laboratório Nacional
de Luz Síncrotron

Português

OVERVIEW

BACK

ABOUT THIS 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


Beamline Email: N/A

Beamline Telephone Number: + 55 19 3512 1141

Coordinator: Amélie Rochet

Coordinator Email: amelie.rochet@lnls.br

Coordinator Telephone Number: + 55 19 3512 5180

For more information on the Beamline Team, check out the Beamline Team’s page here

LAYOUT


OPTICAL ELEMENTS

ElementTypePosition[m]Description
SourceBending magnet0.00Bending Magnet D06 exit A (4°), 1.67 T, 750 $ \mu \rm m$ x 168 $ \mu \rm m$
MirrorVertical focusing mirror6.50800 mm long Rh coated
CrystalCrystal polychromator9.75Water-cooled Si(111)

PARAMETERS

ParameterValueObs. | Condition
Energy range [keV]5 - 14Si(111)
Energy resolution [$ \Delta$E/E]$ 13.1 \times 10^{-5}$Si(111)
Energy band-pass [eV]Hundreds of eV-
Beam size at sample [$ \mu \rm m^2$, FWHM]150 x 200at 8 keV
Photon flux at sample [ph/s]$ 2 \times 10^{11}$at 8 keV

INSTRUMENTATION

InstrumentTypeModelSpecificationsManufacturer
DetectorArea detectorPylon2048F-Princeton Instruments
FurnaceCapillary, 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 2.0/2.4LNLS in-house development
FurnaceTubular, provide attachments to gas lines-Max. temp.: 1000°C Max. heating ramp: 20°C/min Pellet sample with a diameter of 13 or 6 mmLNLS in-house development
Mass flow controllers--Gas flow [mL.$ \rm{min}^{-1}$]: 0.2 - 750BROOKS
Gas cylinders--Pure gases: Ar, He, N2, synthetic air Gas mixture (% diluted in He): CO (20%), O2 (5 and 40%), H2 (5%), CO (5%), NO (5%), CH4 (20%), C3H8 (20%), C4H10 (30%), C2H4 (3%), C3H6 (5%), H2S (5%)-
Thermoregulated bath-TE2005Down to -10°C and up to 80°C. Control accuracy of 0.1°CTecnal
Mass spectrometerGas analysis systemOmniStarTungsten (standard) filament. Mass range 1-100 amu. Gas flow rate 1-2 sccm. Qualitative and quantitative gas analysisPfeiffer Vacuum
Liquid cell--Optic path length [mm]: 0.3 – 7.5LNLS in-house development
Potentiostats/Galvanostats-N series 273A-Autolab EG&G
Diffractometer4 circle424-511.1For sample alignment ($ \theta$, $ 2\theta$, $ \phi$, $ \chi$) = 0.001°Huber
Electromagnetic coilsMagnetic field-Up to 1.5 TLNLS in-house development
Rotary permanent magnetMagnetic field-Up to 0.9 TMagnetic Solutions
Voltage/Current power source-BOP-GL 1KW4 quadrant bipolar power supply. ($ 0 \rm to \pm 50 \rm V_{dc}$) ($ 0 \rm to \pm 20 \rm A_{dc}$)Kepco
Picoammeter-6485-Keithley
Cryostats--Down to 15 K and up to 420 KARS
High-pressure cellHigh-pressure Diamond anvil cellMembrane and screw drivenUp to 80 GpaLNLS 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.

 

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.

It is recommended that the proposer contact the beamline staff to obtain any information required for preparing their proposal prior to submission and for preparing for beamtime. For time-resolved XAS studies, please contact Amélie Rochet (amelie.rochet@lnls.br), for XMCD studies, please contact Narcizo M. Souza Neto (narcizo.souza@lnls.br).

 

PHOTOS

DXAS: Visão Geral / Overview



Português:
Visão Geral da Linha DXAS.

English:
DXAS beamline overview.

DXAS (2)



Português:


English: