Beamline Layout

Introduction

Beamline Overview
Overview

VESPERS (Very sensitive Elemental and Structural Probe Employing Radiation from a Synchrotron) is currently installed and under commissioning at the Canadian Light Source. The objective of VESPERS is to deliver a micro-focussed hard X-ray beam to solid materials in such a manner that a microscopic volume can be analyzed by X-ray Diffraction (XRD) analysis and X-ray Fluorescence (XRF) spectrometry, either simultaneously or sequentially.  In addition, it should also be possible to obtain X-ray Absorption Spectrometry (XAS) measurements on the same sample volume. Therefore, this is a microprobe capable of providing a high level of complementary structural and chemical analytical information

Laue XRD will be the principal structural analytical technique. Laue diffraction uses polychromatic X-rays to diffract from many crystallographic planes in a material without the necessity of rotating the sample in the X-ray beam. However, to be able to index reflections from all crystal planes there is an additional requirement to be able to switch the bandwidth of the incident radiation from pink to near monochromatic in a routine manner. Therefore, the VESPERS monochromator is equipped to produce X-rays with several widely differing bandwidths.

X-ray fluorescence is used to detect the presence of different chemical elements within the analytical volume. The sensitivity and speed with which a particular element is detected depends on many factors: the X-ray flux, the excitation energy of the fluorescence line used and the background from X-rays scattered from other elements.  Since the VESPERS monochromator can produce a range of X-ray energies and bandwidths, it is possible to alter the excitation conditions to suit the analytical requirement. For example, for highest analytical counting speed and multi-element detection, a band pass of 10% or even pink radiation might be selected, while for higher sensitivity (but lower counting speed), a band pass of 1% or even 0.01% could be chosen.

For XAS analysis, the availability of a very narrow bandpass setting also allows the X-ray absorption edge of a particular element to be scanned, thereby permitting the chemical state of a particular element to be sensed (e.g. XANES analysis). The small size of the X-ray beam is competitive with other synchrotron microbeams, as normal operation will be in the range of 2-4 micrometres, but sub-micrometre beam sizes will be achievable.

VESPERS Beamline Layout

Overview

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Source
Bending Magnet
Energy Range
6 – 30 keV
Wavelength
2.0 – 0.4 Å
Resolution Δ E / E @ E
Si(111) – 10-4
MLM2 – 10-1
MLM1 – 10-2
Pink Beam
Flux ( γ /s/0.1%BW) @ 100 mA
Si-111 ~ 2 x 109 @ 15 keV
MLM1 ~ 1 x 1011 @ 15 keV
MLM2 ~ 4 x 1011 @ 15 keV
Spot size (Horizontal x Vertical)
(2 – 4) µm x (2 – 4) µm
Description:
VESPER is a hard x-ray microprobe capable of providing a high level of complementary structural and analytical information. The techniques of x-ray diffraction and x-ray fluorescence spectroscopy are employed to analyze a microscopic volume in the sample. Multi-bandpass and pink beam capability are built in to meet variable requirements.
Endstation(s):
  • Microprobe
  • Diffraction (CCD Camera)
  • Fluorescence (Solid State Detector)
  • Ion Chambers
Techniques:
  • Microprobe
  • X-ray Laue Diffraction
  • X-ray Fluorescence Spectroscopy
  • X-ray Absorption Near Edge Structure
  • Differential Aperture X-ray Microscopy
  • Multi-Bandpass and Pink Beam capability
Optics:
Compounding focusing, multi-stripe mirrors, crystal and multilayer monochromator, KB mirrors