Acquiring Line Scans
Line Scans in AugerMap 2 are different from other acquisitions in that the
result is a graph of one line, as opposed to an image. Functionally, the data is
acquired in a manner similar to that of SEM and elemental images, but at one-pixel width. Therefore, the data is graphed (as opposed
to being displayed as a grey-scale image).
Since line scans can be acquired much more quickly than full images, you can
acquire higher resolution spatial data, and spend more time on each point,
resulting in a better signal-to-noise ratio.
With AugerMap 2, you can mix both SED and ABS lines, as well as elemental
lines. The SED or ABS line can give a good topographic reference for the element. Note that you can only mix SED with non-SED lines if you have a digital SED
multiplier control.
Defining a Line
With AugerMap 2, you can place a line anywhere on a map, in any direction.
Note that, when data is acquired, the orientation is normally from the top-left
of the line.
To define a line, first select the image you wish to define the line on.
Ensure you haven’t selected any other objects on the image (such as annotations). Then, click Line from the Acquisition menu. The cursor will change to a cross-hair. Click-and-drag (hold down the
left mouse button, move the mouse, then release when done) the cursor from one
end of the line to the other (it doesn’t matter which end you start at). You can start “outside” the image if you wish to catch the edge.
Once you release the mouse, you’ll be presented with the “Setup Line Scan Acquisition” dialog.
Line Scan Acquisition Dialog
From here, you can setup all the SEM and/or elemental region parameters for
this line scan.
Comment
Type a comment in this field (optional) for the selected line scan. The
comment will also appear in the Project Window, and on the printout, so it can be a useful reference.
Resolution
Use this drop-down box to select the resolution (number of data points) of the
line scan. The choices available are 64x64, 128x128, 256x256, 512x512, and
1024x1024. The line scan resolution is unaffected by the resolution of the image
it was defined on (or any other image) – it is independent. Therefore, you can choose a 1024x1024 line scan even if
the image you defined it on was 64x64.
Sem Lines
SEM Line List
The SEM Line list is a list of all the SED and ABS video lines for this line scan. To add
an SED line, simply click the Add SED button. To add an ABS line, click the Add ABS button. To remove a line, select the line from the list and click the Remove button.
Sweeps
For each line selected, you can set the number of times the data is collected
(and averaged) for each pixel on this line. For SEM lines, 1 sweep is usually
enough, however, if you are encountering unwanted noise, adding sweeps may be
helpful.
Elemental Lines
Elemental Line List
The Elemental Line list is a list of all the elemental lines for this line scan. To add an
elemental line, simply click the Add button. To remove an elemental line, select the line from the list and click
the Remove button. To remove all the elemental lines, click the Remove All button.
The rest of the parameters reflect the selected element. This is reflected in
the text of the group box below the list.
Energy
These parameters determine what kinetic energies will be used to acquired data
for the selected element. Each element can be acquired using data from the
peak energy only (not normally recommended), from the peak minus one background
energy (recommended), and from the peak minus the intersection of two
backgrounds (used in special cases).
The Peak energy is always selected. To select either the Background E1 or Background E2 energies, check the boxes next to the edit fields. Note that you cannot use
the Background E2 energy unless the Background E1 energy is selected.
The default values for the peak and background energies are provided by the element table. However, these values are not always recommended, as they will often not
result in good data. The best way to obtain these values is to use AugerScan to
do a quick survey of the area.
You must always specify a peak energy by entering a value in the Peak energy field. This energy should normally be the actual maximum count value
of this element’s signature.
The Background E1 energy is normally a kinetic energy (higher than the peak value) at which the
signature of the peak reaches a minimum. When this energy is selected, the
resulting data is the Peak – Background E1, which should yield stable, noise-free data.
The Background E2 energy is normally a stable minimum that occurs at an energy lower than the
peak energy. When this background is selected, the actual background used (for
peak – background data) occurs at the intersection of the peak with a line drawn
between the E1 and E2 backgrounds. This is useful when the E1 (higher energy)
background is fluctuating, which may occur if there is another peak near this
higher energy.
Time Per Step
This value determines the amount of time (in milliseconds) spent acquiring
data at each energy, for each point on the line. For example, if you were using
the peak and one background, data would be acquired at 50ms for the peak and
50ms for the background, for a total of 100ms. Note that the total time is
affected by the number of sweeps (total time = time/step * number of sweeps)
The default time per step is 50 msec.
Sweeps
For each line selected, you can set the number of times the data is collected
(and averaged) for each point on this line. The default number of sweeps is
determined by the element table. Some elements need to be collected for a longer time to build counts and
average out the noise. Although the total data collection time is the number of
sweeps times the time/step, it is usually better to add sweeps then to add
time/step.
Acquisition Control
To cancel the rest of a line scan acquisition click Stop Now from the Acquisition menu. Note that this removes all previously collected data (since it is
incomplete).
After Acquisition
You can adjust the global properties of all line scan graphs (colors, line
styles, etc.). Click here for more information.
You can also edit the line scan to remove regions and apply topographic correction.
Lastly, saving, exporting and printing commands are covered in the File Management topic.