# OVERVIEW

BACK

Warning! This beamline is currently not available to users.

The XAFS1 beamline is an experimental station dedicated to X-ray Absorption Spectroscopy in the hard x-rays energy range (4 to 23 keV). This beamline is used in the study of the atomic-level structure as well as in the electronic and magnetic properties of matter, finding applications in a wide range of scientific fields, such as materials science and solid state physics, chemistry, earth sciences and biology. Available techniques include high-edge resolution (XANES) and fine structure spectroscopy (EXAFS).

The XAFS1 is a 1.67T bending magnet beamline open to users since July 1997. At the second semester of 2016, this beamline was closed for external users and is conditionally available through Fast Track operation and since then XAS spectra can be collected only in transmission mode.

For usual transmission-mode experiments, three chambers are used. The first one is coupled to the beamline, the second is used for detecting the signal after the sample, and the third is used for measuring a reference sample or doubling the data set. Some sample environments as cryostats, and inert gas chambers are available to users at the XAFS1 beamline.

The experimental station is equipped with a granite table, supporting a 1.60 m long rail aligned to the beam direction on which are mounted an XY remote-controlled sample holder, the detectors, and experimental facilities. The granite table can withstand a maximum weight of 300 kg, and track the vertical position of the beam with an accuracy of 1 mm over a 120 mm stroke. In order to keep the beam spot at the same position on the sample, this track is performed automatically during an energy scan, in fact, the changes in beam offset are important only for rather low energies for most applications, i.e. above 8 keV, the tracking is blocked.

## CONTACT

Coordinator: Daniela Coelho De Oliveira
Coordinator Email: doliveira@lnls.br

# OPTICAL ELEMENTS

ElementTypePosition[m]Description
SourceBending Magnet-Bending Magnetic D04 exit B (15°), 1.67T,
Pre-mono SlitsTwo 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.6.5Two water-cooled slits system. Vertically sets the resolution of the beam profile at sample holder.
MonoChannel-cut Crystal7.7water-cooled Si(111) and Si(220)
Post-mono SlitsTwo 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.9.2Without refrigeration, these slits are used to eliminate the spurious background radiation.

# PARAMETERS

ParameterValueObs. | Condition
Energy range [keV]4-23Si(111), Si (220)
Energy resolution [$\Delta$E/E]$1.31 \times 10^{-4}$Si (111)
Energy resolution [$\Delta$E/E]$5.37 \times 10^{-5}$Si (220)
Beam size at sample [$\mu \rm m^{2}$, FWHM]$\approx$1000 x 1000at 10 keV
Beam divergence at sample [$\rm mrad^{2}$, FWHM]1 x 0.1at 10 keV
Flux density at sample [ph/s/$\rm mm^{2}$]$10^{9}$at 7 keV, Si (111)
Flux density at sample [ph/s/$\rm mm^{2}$]$10^{8}$at 7 keV, Si (220)
Harmonic content<1%For E>5 keV

# INSTRUMENTATION

InstrumentTypeModelSpecificationsManufacturer
DetectorIon chambers-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
CryostatsCooling power He closed cycle cryocoolerDE-202 Cryocooler series(T min = 4 K)ARSCryo
Inert Gas or Vacuum Chamber--Helium, Argon, Nitrogen or Vacuum ambient under flow or sealedLNLS in-house development

# CONTROL AND DATA ACQUISITION

All beamline controls are done through EPICS (Experimental Physics and Industrial Control System), running on a PXI from National Instruments and communicates with Galil/Parker controllers. The beamline controls and data acquisition are made by a linux workstation running Spec. For user-friendly interface in Motif Editor and Display Manager (MEDM) is used as a graphical interface to display and control the beamline devices.

# APPLYING FOR BEAMTIME

This beamline is currently not available to users.

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.