Proton Microprobes

Proton microprobes represent a natural evolution of the PIXE analysis work which seek smaller area beams for lowered minimum detectable mass levels and allows an expansion of such analyses to encompass even the spatial 

The sensitivity of 10-100 ppm has been obtained for a current of 1-100 nA by using the microbeam. 

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Grime, G.W. (1999) Proton microprobe (methods and background) in Encyclopaedia of Spectroscopy and Spectrometry, J.C. Lindon, G.E. Tranter J.L. Holmes, Ed. Academic Press, Chichester, pp. 1901-1905. 

Figure 3. Starting with the binocular microscope, discriminatory power increases in a counterclockwise direction, as indicated by the circular background. Variations in flowline width reflect the differential sampling capabilities of the techniques. Special petrological techniques include X-ray diffraction, electron and proton microprobe, staining, and heavy mineral separation.

Malmqvist KG. Proton microprobe analysis in biology. Scanning Electron Microsc 1986 IB 821-845. 

Some of the disadvantages of the electron-probe method may be overcome, as in other methods, by the use of complementary techniques. Such techniques can complete the results obtained by electron microprobe. For instance, the introduction of a proton microprobe [39], which is much more sensitive (by two orders of magnitude) than the electron microprobe, and may be used with very good results in geochemical and cosmochemical studies. 

NMR spectra heteronuclear gold cluster compounds, 39 345-348 Phalaris canariensis esophageal cancer, 36 144-145 scanning proton microprobe, 36 149 structural motifs of silicas, 36 146 Pharmaceuticals, 18 177 Phase transitions, in chalcogenide halide compounds, 23 332, 408, 412 [PhCHjMejNAlHjlj, 41 225-226 [(PhCH2)jNLi]3 molecular structure, 37 94, 96 in solution, 37 107-108... 

Cahill, T. A, Proton Microprobes and Particle-Induced X-Ray Analytical Systems, Annu. Rev. Nucl. Part. Sci., 30, 211-252 (1980). 

Morrison et al. (1981) have used the proton microprobe to map K, Ca, Mn and Co by scanning across a leaf. The instrument is similar to the electron microprobe, but has a sensitivity of the order of 1 -10 pg g 1. It can also be operated in air instead of vacuum, these two differences rendering the method very suitable for plant analyses. The results showed that in the region of potassium deficiency there were elevated levels of calcium and cobalt. 

G.E. Coote, R.W. Gauldie, W.J. Trompetter, I.C. Vickridge, A. Markwitz, Twenty years of proton microprobe research in biominerals a tribute to Graeme Ernest Coote, 1935-1997, Nucl. Instr. Meth. B158 (1999) 1-5. 

G.W. Grime, M.H. Abraham, M.A. Marsh, The new external beam facility of the Oxford scanning proton microprobe, Nucl. Instr. Meth. B181 (2001) 66-70. 

O Reilly S. Y., Griffin W. L., and Ryan C. G. (1991) Residence of trace elements in metasomatized spinel Iherzolite xenohths a proton-microprobe study. Contrib. Mineral. Petrol. 109, 98-113. 

Ewart A. and Griffin W. L. (1994) Application of proton-microprobe data to trace-element partitioning in volcanic rocks. Chem. Geol. 117, 251—284. 

The application of the Oxford scanning proton microprobe to these studies was of particular importance in the monitoring of trace ele-... 

Ryan C G, Cousins D R, Sie S H, Griffin W L, Suter G F and Clayton E 1990 Quantitative PIXE microanalysis of geological material using the CSIRO proton microprobe Nucl. Instrum. Methods B 47 55... 

Lindh, U. and Tveit, A.-B. (1980) Proton microprobe determination of fluorine depth distributions and surface multielement characterisation of dental enamel. J. radioanal. Chem., 59, 167-191. 

The Proton Microprobe. No discussion of ion beam analytical systems would be complete without mention of the ultimate ion beam system— the proton microprobe. As shown in the excellent review articles by Cookson (5) and Martin and Nobiling (19), ion beams can be prepared with dimensions of a micron or so. Such finely focussed ion beams can be supported by the nuclear or atomic analytical methodologies mentioned above, with PIXE being the most widely used. Since the PIXE system s fractional mass sensitivity is not changed by beam area, one can have a 1-ppm measurement made over an area of 10 cm, yielding mass sensitivities of 10" g or so in a nondestructive multiele-mental analysis as shown in Figure 6. No other method exists that can obtain such data, so the role of ion beams is well foimded. Explosive growth of these expensive systems has occurred in the past five years, but the cost has limited applications to most environmental samples. 

Acronyms I PM A, SIMP (scaiming ion microprobe) PMP (proton microprobe)... 

Scanning ion microprobe and scanning proton microprobe are very useful techniques for in situ element or isotope distribution analysis. With protons or heavy ions, the mean free path between ionising events is generally much shorter than the specimen thickness and hence multiple inelastic scattering occurs. The energy loss spectrum is then a measure of specimen thickness. If the specimen thickness exceeds the range of the slow heavy ions in an IMP (ion microprobe) then trans-... 

Figure 2 Detection limits as a function of Zfor two proton energies and for thin and thick specimens. The minimum detection limit is defined here as the concentration giving a peak-to-background ratio of 1. The calculations are done for a carbon matrix. (Reprinted with permission from Vis RD (1985) The Proton Microprobe Applications in the Biomedical field. Boca Raton, FC CRC Press CRC Press.)...

The main trend in PIXE analysis had also been on the development and extensive application of proton microprobe (beam diameter = micrometer) as it offers better spatial resolution, generates a far lower background resulting in better detection ability. 

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