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CSIRO-GEMOC Nuclear Microprobe CSIRO
Interactions of MeV ions with matter permit microanalysis and imaging of sample constituents using excited X-rays (PIXE - Proton Induced X-ray Emission), gamma-rays from nuclear reactions (PIGE - Proton Induced Gamma-ray Emission), outgoing nuclear reaction particles (NRA - Nuclear Reaction Analysis), elastically scattered ions (BS - Backscattering), (ERDA - Elastic Recoil Detection Analysis), or visible and infrared emissions from the sample (IL - Ionoluminescence).

The ion beam can also be channelled down crystal axes and planes. Many of these techniques can be combined with channelling to study the lattice location of species (CCM - Channelling Contrast Microscopy).

MeV protons are very penetrating while producing very little sample damage. These qualities permit the in situ, non-destructive analysis and imaging of buried structures such as solid and fluid inclusions in minerals.

Proton Induced X-ray Emission

Proton Induced Gamma-ray Emission

Backscattering

Elastic Recoil Detection Analysis

Nuclear Reaction Analysis

Channelling Contrast Microscopy

Ionoluminescence



Return to NMP microanalysis

CCM - Channelling Contrast Microscopy

MeV ion beams, directed onto oriented crystalline solids, can channel down crystal axes and planes over rocking angles of ~1° (angle depends on ion mass, energy and axis order). Backscattering and PIXE yields from impurity atoms are reduced when the impurity is substitutional on the crystal lattice (or enhanced for certain interstitial sites) due to reduced (enhanced) interaction with the passing ions. This provides analysts with a tool for determining whether an impurity element (a precious metal, for example) is in the structure of a mineral, or simply present in some sub-microscopic inclusion phase.



Exploratory work by Jamieson and Ryan (1993) has shown that channeling can be combined with microbeam techniques to provide a powerful tool for characterizing the crystallographic residence of precious or geochemically interesting trace elements in minerals. A good example of the application of the technique is the investigation of the crystallographic residence of gold in pyrite.

Jamieson and Ryan (1993) succeeded in channeling beams of 3 MeV protons and 2 MeV He+ ions into the <210> oriented pyritohedral face of a 400 µm pyrite grain, from the ore-zone of the Emperor Mine, Fiji. Comparing spectra collected while channeling (yellow curve) and at a random orientation (pink curve), they observed reduced scattering yield from trace Au in the channeling case consistent with a ~50% substitutional Au component. This result confirmed the significant solid-solution Au component observed in the PIXE true elemental imaging.

Further Reading:

  • M.B.H. Breese, D.N. Jamieson and P.J.C. King, "Materials Analysis using a Nuclear Microprobe", Wiley and Sons, New York, 1996.
  • C.G. Ryan, "The Nuclear Microprobe as a probe of earth structure and geological processes", Nucl. Instr. Meth. B104 (1995) 377-394.
References:

For further information contact: Dr. Chris Ryan via email: (Chris.Ryan@csiro.au)

+61-2-9490 8673
+61-2-9490 8909

CSIRO Exploration and Mining
PO Box 136
North Ryde NSW 2113
Australia


CSIRO-GEMOC Nuclear Microprobe
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