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XAS
BRIGHT Beamlines

Medium Energy X-ray Absorption Spectroscopy Beamline (MEX-1 and MEX-2)

Capability Summary and Techniques

The MEX-1 and MEX-2 beamline utilises one bend magnet as the source and will operate independently and has been designed to be experimentally flexible, extending and complementing the suite of the X-ray spectroscopy techniques already available at the Australian Synchrotron.

At MEX, the instrumental capabilities are focused on:

  • Spanning the soft and hard X-ray energy regimes (1.7 – 13.6 keV).
  • Minimising radiation damage (by using relatively larger beam sizes and lower flux densities).
  • Easily tunable beam sizes (from µm to mm).
  • Routine, high-quality X-ray Absorption Spectroscopy (XANES and EXAFS) of bulk specimens.
  • Routine use of non-ambient sample environments.
  • High energy resolution fluorescence detection (HERFD) X-ray absorption spectroscopy.
  • High quality micro-spectroscopy (2.0 – 13.6 keV).

MEX-1

This beamline will offer monochromatic X-rays (from a Si<111> double crystal monochromator) at one of three endstations, with variable beam sizes at a fixed height from the floor. The different MEX-1 endstations will not be able to operate simultaneously.

Multiple modes of operation:

  1. Bulk XAS (EXAFS and XANES) 3.5 – 13.6 keV in transmission and fluorescence. Sample in helium gas environment at ambient or variable temperatures (10-300K).
  2. Bulk HERFD-XAS (EXAFS and XANES) 3.5 – 13.6 keV, via a 5-crystal 0.5m Johann-type spectrometer. Sample environment: variable temperature (10 – 300 K), helium gas atmosphere and/or vacuum (continuous gas flow cryostat).
  3. Range of non-ambient sample environments, including electrochemical cell, flow cell, pressure cell or furnace. Please get in contact with the Beamline Team to discuss the details.
  4. Scanning X-ray fluorescence microscopy, optimised for microspectroscopy (EXAFS and XANES) 2.1 – 13.6 keV, harmonic content < 10-4. Microfocus will be adjustable between 2 and > 10 μm. Sample in helium gas atmosphere, variable temperature (80 – 500 K) via liquid nitrogen cooled He(g) cryostream.

MEX-2

This branch line will offer low energy monochromatic X-rays – from either InSb<111> or Si<111> – double crystal monochromators at a fixed position and with a maximum beam size of 2 x 5 mm2. Slits can be used to reduce the beam profile on the sample. Sample environment: variable temperature (~10 – 500 K), helium gas atmosphere and/or vacuum.

Multiple modes of operation:

  1. Bulk XAS (EXAFS and XANES) 1.7 – 3.5 keV in transmission, drain current and fluorescence.
  2. Bulk HERFD-XAS (EXAFS and XANES) 1.7 – 3.5 keV via single crystal, dispersive refocusing Rowland circle geometry-type spectrometer.

Scientific Applications

The MEX beamlines have been designed to offer a range of capabilities for undertaking XAS measurements across a wide range of scientific applications, with a particular emphasis on in situ and in operando experiments. Collecting high-quality data while minimising the dose delivered to the sample is expected to be another strength. MEX will also bring the new and powerful tool for chemical research, HERFD-XAS, to the Australian Synchrotron, opening new avenues for material characterisation.

Human Health and Biology 
  • Studies of the chemistry and function of metalloproteins in biology. As much as one-half of all biological catalysts require a metal for activity, and iron-containing metalloproteins like haemoglobin perform vital functions like storing and transporting oxygen throughout the body.  Understanding the molecular-scale structure, function and mechanism of such proteins is essential in determining how metal biology contributes to health and disease.
  • Oxidative stress in cells and tissues contributes to diseases of ageing like dementia and can be quantified by determining the chemical ratio of sulfur-containing thiols and thiolates. The distribution and abundance of these molecules within cells are also crucial to a myriad of biological processes, including tumorigenesis.
  • The chemical state and distribution of phosphorus is key to understanding cellular the structure and well-being of bone and teeth.
  • K-edge XAS is an ideal tool to study the binding and transport of potassium and calcium ions by coronavirus viroporins, information useful for screening drug candidates during pre-clinical development.
Food, agriculture, and plant biology

In soils and minerals, silicates, phosphates, sulfur and chloride ions are common, and X-ray absorption spectroscopy of these ions can reveal the chemical environment in which they are present. When combined with the XAS on metals present in the same milieu, superior definition of the chemical speciation and spatial distributions will be possible compared to relying on a metal K-edge XAS alone. Such information is invaluable for the study of soil salination, the efficacy of fertilisers in agriculture, plant growth and micro-nutrient transport, as well as the distribution and bioavailability of essential micro-nutrients in food.

Advanced materials, catalysis, and chemistry

The target energy range of the MEX beamlines will open up numerous avenues of research into advanced materials.

  • Silicon is the backbone of the electronics industry and more exotic semiconductors such as indium phosphide are emerging for specialist applications. The ability to characterise these materials post modification allows the details of atomic structures that directly impact performance and suitability for applications in electronic components to be observed.
  • Many emerging materials technologies include amorphous and micro-crystalline materials, nano-particulates and composites.  The MEX beamlines can investigate the chemistry and local atomic structure of these materials that often ill-suited for characterisation via diffraction-based techniques. 
  • Silicon has multiple commercial and a better understanding of the structure/function relationship of amorphous and crystalline phases of silicon, and silicon oxide is relevant to several industrial and engineering process but critical to the development more efficient silicon-based photovoltaics.
Environmental studies

Studies of numerous pollutants in the environment and their decomposition are readily studies using the MEX beamlines.  Examples include:

  • The redox status and speciation of sulfur-containing compounds in the environment;
  • The distribution and speciation of inorganic and organophosphate pollutants and their breakdown;
  • The speciation of organochlorine pollutants and their breakdown to inorganic chlorides. Chlorine K-edge XAS for example, can be used to study the fate of NaCl in coal to determine temperature thresholds for the formation of highly undesirable organochlorine by-products of coal combustion.
Earth Science and minerals formation

By making use of non-ambient sample environments, experiments designed to reveal the speciation of complexes under hydrothermal conditions or lead to a better understanding of geochemical process like the transport and deposition of precious metals through the earth’s crust can be undertaken. Examples include:

  • Studies of acid sulfate soils.  Sulfur K-edge XAS can be used to identify reactive intermediates in reduced sulfur sediments to characterise biotic versus abiotic reaction chemistry, as well as to understand the chemistry in different acid sulfate soil environments.
  • Numerous precious metals are present in ore bodies as sulfide minerals.  The MEX beamlines can be used to study mineral formation processes, as well as methods to optimise their extraction.
  • The redox state of Fe and S in glasses and melt inclusions. The oxygen fugacity of magmas can be inferred from Fe redox state. The solubility of sulfur in magmas, and hence magmatic ore deposit formation, is highly dependent on the speciation of sulfur. The MEX1 microprobe will permit microspectroscopic mapping at 2-10 microns spatial resolution.
Cultural Heritage, Archaeology, and Arts

Many of the pigments used in artworks and prevalent in archaeological artefacts contain metals as well as sulfur-containing, chloride and phosphate ions. 

  • MEX measurements of artwork and cultural heritage artefacts will assist significantly in the identification of pigments, as well as their ageing and weathering processes. 
  • In combined with historical records, characterisation of such pigments and dyes are essential in establishing provenance, and also provides vital information to support curatorial practices and restoration projects.

When MEX studies are combined with the dating of samples, information such as ancient cultural practices and trade associations lead to important understandings of many aspects of the development of civilisation and the preservation of cultural heritage worldwide

Technical Information and Specifications

Beamline Layout

Beamline layout 1 - MEX 1 2

Beamline layout 2 - MEX 1 2

Beamline layout 3 - MEX 1 2

Technical Specifications

View MEX 1 and 2 Technical Specifications

Number of Beamlines

MEX-1: monochromatic, 2.1 – 13.6 keV

MEX-2: monochromatic 1.7 – 3.5 keV

Number of Endstations

MEX-1: 3

MEX-2: 1

Source

 

Bending magnet (BM12-1)

 

 

 

Optics

MEX-1

 

 

Mirror 1 (M1) –

Vertical collimation

 

- Fixed, flat Si substrate

- Cylindrically bent

- Bounce up (4.75 mrad)

- Exchangeable C, Ni and Rh stripes

 

Double crystal monochromators

 (DCM)

- Si<111>, 𝛥E/E ≈ 1.4 ×10-4

- Crystal azimuth (𝜙) 0° and 30°

- Vertical bounce

 

Mirror 2 (M2) –

Vertical and horizontal focussing

- Cylindrical + flat Si substrate

- Elliptically bent

- Bounce down (4.75 mrad)

- Exchangeable C and Rh stripes

 

 

 

 

MEX-2

 

 

Front end mirror (M1) –

Vertical collimation

- Fixed sagittal cylinder

- Horizontal bounce (15 mrad)

- Cr stripe

 

Mirror 2 (M2) –

Horizontal collimating

- Fixed cylinder

- Horizontal bounce (15 mrad)

- Cr stripe

 

Double crystal monochromators

 (DCM)

- Si<111>, 𝛥E/E ≈ 1.4 ×10-4

- InSb<111>, 𝛥E/E ≈ 3 ×10-4

- Crystal azimuth (𝜙) 0°

- Vertical bounce

 

 

 

Endstations

MEX -1

 

 

XAFS Station

- EXAFS/XANES

- 3.5 – 13.6 keV

- Transmission and florescence (4 el. Si SDD)

- Sample temperature 10 – 300 K (in He(g))

- HERFD-XAS:

> 0.5 m Johann-type crystal analyser

> 5x spherically bent crystals

- Non-ambient sample environments

- Beam size 0.15 – 0.5 x 1.8 – 7 mm2

- Flux 3 x 1011 ph-1 sec-1

 

Microprobe station

- µEXAFS/µXANES

- 2.1 – 13.6 keV

- 3 el. Si SDD

- 2-moment KB mirror system

- Exchangeable C and Rh stripes

- Beam size: 2 – >10 µm

- Flux 108 ph-1 sec-1 µm2

- Sample in He(g)

- Sample temperature 80 – 500 K

- Scan range < 80 × 80 mm

 

MEX-2

(“Low energy station”)

EXAFS/XANES

- 1.7 – 3.5 keV

- Transmission, drain current and florescence

(4 el. Si SDD)

- HERFD-XAS:

>Dispersive refocusing Rowland geometry

>Single cylindrically bent, Si<111> Johann analyser

- Beam size 0.1 – 2 x 0.1 – 5 mm2

- Flux:

Si<111> 5 x 1010 ph-1 sec-1

InSb<111> 1 x 1011 ph-1 sec-1

- Sample in He(g) or vacuum

- Sample temperature 10 – 300 K

Beamline Status

View beamline status

Date

Status

2017 July

Project started

2018 January

Investment Case (IC) approved and endorsed by ANSTO

2018 June

Conceptual Design Report

2019 March

PDS Contract Placed (Axilon, Germany)

2019 July

Technical Design Report

2019 August

DCM (X2) Contract Placed (IDT, UK).

2020 February

Crystal Spectrometer Order Placed (Huber, Germany)

* Plus delay to be determined following resolution of covid-19 related restrictions

*2020 – 2021

Installation of Hutches and User cabin

*2021

Installation of PDS and DCMs

*2021

Installation of Endstations

*2021

Hot Commissioning begins, includes expert users

*2021 Q3

First User Experiments; Beamline fully commissioned over the next 12 months

Staff

Mr Mohamed Elrabiey – Project Manager

Dr Chris Glover - Lead Scientist

Dr Jeremy Wykes - Beamline Scientist

Dr Simon James - Beamline Scientist

Mr Ben Pocock – Mechanical Engineer

Mr Ben Baldwinson – Senior Controls Engineer

Dr Letizia Sammut – Senior Scientific Software Engineer

Alex Palma - Scientific Software Engineer

Beamline Advisory Panel

Professor Peter Lay (Chair) – University of Sydney

Prof. Dr Serena DeBeer - Max Planck Institute for Chemical Energy Conversion

Associate Professor Peter Kopittke - The University of Queensland

Dr Rosalie Hocking - Swinburne University of Technology

Dr Mark Hackett - Curtin University

Dr Andrew Berry – Australian National University

Contact

as-mex@ansto.gov.au