Micro-PIXE elemental maps

Figure 4.22. Micro-PIXE elemental map for Si taken on coarse particles (<1.2 pm) within a total scanning area of 25 pm x 25 pm. (Kasahara et al. 2001.)...

An example of micro-PIXE elemental maps shown in Rg. 5 was drawn on a 25 pm X 25 pm scanning area including a single large dust partiele. In Fig. 5, row and col are pixels corresponding beam sean area. In addition, the scale bar shows the intensity of characteristics X-ray count. Each elemental map can be drawn on the 128 x 128 pixels by scanning of about 1 pm micro beam on the surface of the individual particles. Several elements in and/or on a single particle (Dpi 7.7 pm) were detected successfully. Soil components (such as Ca, Fe, and K)... 

Fig. 5 An example of micro-PIXE elemental maps taken on individual ADS particles collected on the stage-1 (50% cut-off size 7.7 pm) of LPAI sampler. Scanning area is 25 x 25 pm ...

Fig. 8 Micro-PIXE elemental maps (scanning area 760 x 760 pm ) on a whole single raindrop (0.5 mm diameter) fallen in a yellow rainfall event...

Figure 7 Micro-PIXE elemental maps for the distribution of C, O, Na, Mg, Si, P, S, K, and Fe in root of plant rape (Brassica napus) (size of scanned area 500 x 500pm). (Reproduced with permission from Kertesz Zs, Uzonyi I, and Kiss Az (2003).)...

Figure 7.68 PIXE elemental maps of Ca of The images were obtained at the Nuclear micro-regions (approx. 250 pm2) of selected Microprobe (NMP) facility of iThemba LABS,...

The sample environment was filled with He gas to prevent the argon X-ray emission from air. Beam scanning, data acquisition, evaluation and the generation of elemental maps were controlled by a computer. Micro-PIXE measurements were performed with a scanning 2.5MeVH+ microbeam accelerated by the 3 MV single-end accelerator. The beam diameter was 1-2 pm, so that individual particles could be analysed. The beam current was < 100 pA and the irradiation time was about 3(M0 min. 

Weiersbye, I.M., Straker, C.J., Przybylowicz, W.J., 1999. Micro-PIXE mapping of elemental distribution in arbuscular mycorrhizal roots of the grass, Cynodon dactylon, from gold and uranium mine tailings. Nucl. Instrum. Methods Phys. Res., Sect. B. 158, 335-343. 

As mentioned above, it is possible to maintain insoluble particles, which were scavenged by raindrop, on individual raindrop replicas by collodion film technique. These insoluble particles are the target of micro-PIXE analysis. An example of the elemental map for Si, S, Cl, K, Ca, and Fe is drawn in Fig. 8. Each elemental map was drawn on the 128 x 128 pixels by scanning of about 1 pm micro beam on the sample surface. Because the residual particles were retained on a raindrop replica as several clusters, we could not radiate the microbeam to individual residual particles. However, the visualized elemental maps of six element types in several particle clusters enable us to estimate the chemical mixing state of raindrop residual particles. In addition, it is also presumed that the chemical transformation of dust particles is made by wet scavenging processes. 

Particle-induced X-ray emission (PIXE) is an elemental analysis technique that employs a beam of energetic heavy charged particles (usually protons of 1-4 MeV) to induce element-specific X-ray emission. Depending on the sample material and thickness and on the conditions of the analysis, the technique offers detection limits at the 0.1-10 mg kg concentration level for low-Z matrices. Applied in nuclear microprobes, micro-PIXE combines a high sensitivity with the possibility of providing elemental maps with a lateral resolution in the sub-micrometer range. 

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