XRF Beamline

The XRF beamline is an experimental station dedicated to X-ray Fluorescence Microscopy (XRFM), X-ray Fluorescence Tomography (XFCT) and Total Reflection X-ray Fluorescence (TXRF) analysis in the hard X-rays energy range (5 to 20 keV). The beamline’s focus is on the determination and mapping of trace chemical elements in samples with applications in the fields of analytical chemistry, biomedicine, environmental geochemistry and materials science.

XRF’s source is a 1.67T bending magnet. The monochromator vacuum chamber can be laterally displaced, so that the whole synchrotron spectra can also be used to excite the samples. The experimental facilities include one station consisting of a high vacuum chamber in which grazing incidence x-ray fluorescence experiments can be carried out. The chamber is equipped with remote-controlled XY$\rm \theta$y sample stages and a HPGe solid state detector, optimised for the detection of light element. The whole setup is mounted in the motorised lift table, which allows vertical positioning of the instruments on the plane where the incoming beam is mostly linearly polarized.

Applications include 2D XRF mapping and speciation of trace elements at 20 microns resolution, 3D information of elements in volumetric samples, analysis of very small masses deposited on flat substrate, trace impurities on surfaces of flat samples, chemical depth profiling surface analysis (from sub nm to mm range).

## 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 Fluorescence (XRF) Analysis

X-ray Fluorescence (XRF) is a well-established bulk analytical method for qualitative as well as quantitative determination of several elements in a sample, independent of their chemical form. Depending on the detection system configuration, can be classified as Energy Dispersive (EDXRF) or Wavelength Dispersive (WDXRF) systems.

Setup: X-ray Fluorescence Microscopy (XRFM)

This setup allows performing experiments with an X-ray microbeam. The microfocusing optics consists of a pair of bendable mirrors arranged in the so called Kirkpatrick-Baez configuration (KB). The X-ray microbeam is around 12 microns (vertical) by 22 microns (horizontal) in size. Fully remote-controlled XYZz sample stages can operate in air or under a nitrogen gas environment. The $\rm \mu$-XRF setup also includes an optical microscope and a Silicon Drift Detector (SSD).

Other setups include:

• Setup: Grazing Incidence X-ray Fluorescence Analysis (GI-XRF)
• Setup: X-ray Fluorescence Tomography (XFCT)
• Setup: Total Reflection X-ray Fluorescence (TXRF)

## LAYOUT & OPTICAL ELEMENTS

Element Type Position [m] Description
SOURCE Bending Magnet 0.0 Bending Magnet D09 exit B (15°), 1.67 T , 0.92 mm x 0.57 mm
Mono Double Crystal Monochromator 11.2 Si(111), Si(220), channel-cut type
M1 Elliptical Vertical Micro- focusing Mirror 14.9 Rh coated, RT=334m (center), θ=4 mrad
M2 Elliptical Horizontal Microfocusing Mirror 15.3 Rh coated, RT=334m (center), θ=4 mrad Rh coated, RT = 176m (center), θ

$\theta$

## PARAMETERS

Parameter Value Condition
Energy range [keV] 5-20 Si(111) / Si(220)
Energy resolution [ΔE/E] 10-4 Si(111)
Beam size at sample [µm2, FWHM] 22 x 12 at 10 keV
Beam divergence at sample [mrad2, FWHM] 10 x 1 at 10 keV
Flux density at sample [ph/s/mm2/100 mA] 2 x 108 at 10 keV
Flux density at spot [ph/s/100mA] 2 x 1012 White beam

## INSTRUMENTATION

Instrument Type Model Manufacturer Specifications
Detector Silicon drift AXAS-A 30 mm2 SDD, FWHM ≤ 139eV at 5.9keV KETEK GmbH
Detector Silicon drift AXAS-A 7 mm2 SDD, FWHM ≤ 139eV at 5.9keV KETEK GmbH
Detector HPGe GUL0035 30 mm2 Ultra-LGe, FWHM = 140 eV at 5.9keV Canberra
Cryostat Cryostream Cooler 700 Series Minimum of 173K, with a gas stability of 0.1K Oxford

## 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) are used as a graphical interface to display and control the beamline devices. Point-to-point or continuous scanning (“on-the-fly”) modes of operation can be used for data acquisition in 2D/3D experiments.

## 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.

PÉREZ, C. A., RADTKE, M., SÁNCHEZ, H. J., TOLENTINO, H., NEUENSCHWANDER, R. T., BARG, W., RUBIO, M., BUENO, M. I. S., RAIMUNDO I. M. & ROHWEDDER, J. J. R., Synchrotron Radiation X-Ray Fluorescence at the LNLS: Beamline Instrumentation and Experiments, X-Ray Spectrometry 28, 320–326 (1999). doi: 10.1002/(SICI)1097-4539(199909/10)28:53.0.CO;2-1

The x-ray fluorescence beamline of the Laboratorio Nacional de Luz S´ıncrotron (LNLS) is described. The main optical component of the beamline is a silicon (111) channel-cut monochromator, which can tune energies between 3 and 14 keV. A general description of two experimental stations is given. Beam characterization was done by measuring experimental parameters such as vertical profile and monochromatic flux. These results show that the photon flux at 8 keV in an area of 20 mm2 is 4.2 × 109 photons s−1. The possibility of achieving fine tuning of energies (high resolution) was confirmed. This paper presents some original results derived from the commissioning of the beamline, such as a comparison of detection limits in different experimental conditions, and a novel mechanical system to align capillaries together with a semi-automatic adjustment procedure. So far, there have been several proposals to perform a variety of experiments at this beamline, covering different fields, such as physics, chemistry, geology and biology.

## 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 at the SAU Online website.