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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

PIGE - Proton Induced Gamma-ray Emission

In low energy encounters between ions and atoms, the Coulomb repulsion between the charged ion and the nucleus of the atom prevent any close interaction between the ion and the nucleus. However, MeV energy protons can penetrate the Coulomb barrier on light elements and induce various nuclear reactions. Many of these reaction channels involve the emission of gamma-rays.

Detection of nuclear reaction induced gamma-rays, and detailed characterization of reaction cross-sections, has enabled quantitative analysis methods to be developed. The lower Coulomb barrier of light elements makes PIGE particularly suitable for the analysis of light elements such as Li, Be, B, F, Na, and Al.



A weakness of PIXE is the general inaccessibility of light elements (Z<13). While complimentary tools, such as the EMP help to fill this gap for major elements, providing routine major element data down to at least Na, the lightest elements (e.g. H, Li, B) require nuclear reaction or recoil methods.

The Laboratoire Pierre Sue, Saclay, and the Bruyeres le Chatel nuclear microprobe facility, Paris, have developed nuclear reaction methods for the measurement of 1,2H, 6,7Li, 10,11B, 12C, 14N, 16O, 19F, 23Na, 24,25Mg, 27Al, 28Si, 32S and 35Cl in minerals (Courel et al., 1991; see review by Ryan and Griffin, 1993, and references therein). The isotopes 7Li, 19F, 23Na, 24,25Mg, 27Al, 28Si and 35Cl are determined using (p,p'gamma) reactions (PIGE) at proton energies from less than 2 MeV up to 3.5 MeV, suitable for simultaneous PIXE analysis of heavier elements. A similar approach is taken by the Queen's University group (MacArthur and Ma, 1991). H is determined by elastic recoil detection (ERDA). The remaining isotopes are determined using (d,a), (d,p), (p,a) and (p,a gamma) reactions. The corresponding elemental detection limits for all elements between H and F are 10-50 ppm. For the elements Na and heavier the detection limits grow from ~200 to ~2000 ppm.

The notation used for nuclear reactions, (x,yz), denotes the incident beam particle "x" and the reaction products "y" and "z", where "p" is a proton, "d" is a deuteron (2H), "a" is an alpha particle (4He) and "g" or "gamma" denotes a gamma-ray. "p'" denotes an inelastically scattered proton; it leaves the target nucleus in an excited state.

Further Reading:

  • C.G. Ryan, "The Nuclear Microprobe as a probe of earth structure and geological processes", Nucl. Instr. Meth. B104 (1995) 377-394.
  • M.B.H. Breese, D.N. Jamieson and P.J.C. King, "Materials Analysis using a Nuclear Microprobe", Wiley and Sons, New York, 1996.
References:
  • P. Courel, P. Trocellier, M. Mosbah, N. Toulhoat, J. Gosset, P. Massiot and D. Piccot, Nucl. Instr. Meth. B54 (1991) 429.
  • J.D. MacArthur and X.-P. Ma, J. PIXE 1 (1991) 311.
  • C.G. Ryan and W.L. Griffin, "The Nuclear Microprobe as a tool in geology and mineral exploration", Nucl. Instr. Meth. B77 (1993) 381-398.

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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