Dynamic Analysis PIXE Imaging

These PIXE images were collected using the Nuclear Microprobe, Sandia, Department of Radiation Solid Interactions. The event data were analyzed using the CSIRO Dynamic Analysis method, which enables quantitative, true-elemental images to be un-mixed from the generally complex PIXE energy spectrum. The images shown below are reduced in size in this summary. To view the full image, click on the image.

Dynamic Matrix: G:\IDL\Data\Sandia\MPA3\24\Test-Iodine024.cuts

Sample: Grain: 
Charge: 1.00000
Cal: A= 1.00000, B= 0.000000, Units= keV
Scan: X= 0.000000, Y= 0.000000 mm
X Compress: 1, Y Compress: 1
X Scaled: 1.00000, Y Scaled: 1.00000
X size: 256, Y Size: 256

Processed: 7690846, Bad: 10148001
Valid: 7690110, Clipped: 736

DA Matrix: Cuts
DA Charge: 0.000000

Dynamic Analysis PIXE Imaging

Display Maximum Values
<15 570.% 15-25 1.81E+007 ppm 25-35 2.12E+007 ppm 35-50 1.56E+007 ppm 50-80 924.% >80 184.%

The counting statistics in a single pixel are generally low. This means that there can be large differences in deduced ppm.charge between neighbouring pixels. This is normal. Estimation of concentration in portions of the image involves integrating an average over the region. This averages out much of this statistics variation to yield concentration estimation with low detection limits.

However, these statistics can lead to a misleading colour scale for the image, as the image appears to show concentration variation over a large range at the pixel level. This means that some images show large maximum values despite a generally low concentration. (To help alleviate this problem, use image smoothing filters, or use average concentrations over a selected region, as shown below.)

It should also be noted that overlap and background subtraction may lead to some pixels having negative values. For example, areas with zero concentration will have as many negative as positive pixels. When regions are integrated, all values are averaged and the correct concentration results. However, some images may appear to show areas with positive signal due to statistical fluctuations despite zero average concentration because negative pixels are shown in black.

Average Concentration in Current Region

No specific region was specified.
Sandia, Department of Radiation Solid Interactions © 2002