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6) Click the Save button at the bottom of the sidebar to store the table.
7) Next, enter the mass or density as shown in the Absorber section at the top of the sidebar (Fig. 147), and click
Calculate.
8) Click Save again to store the complete record in the database.
5. MENU COMMANDS
Fig. 149. Adding a New
Constituent to the
Database.
Calculate from Spectra
Selecting this command opens the External Attenuation Sidebar, shown in Fig. 150. External attenuation tables can be built automatically using analysis results (
.UFO
) files, or manually by entering the peak net area rates for specific energies.
Automatic Calculation
In the automatic mode, select the UFO Files for the analysis of two spectra (Reference and Current) and click Calculate.
These two spectra must be the spectrum without the absorber
and the spectrum with the absorber. The two samples should be otherwise as similar as possible. This will produce a table that is the ratio of the net peak areas for all the peaks that are in both spectra. The matching is done by using the identified (library) peak list in both
.UFO
files. The calculated table is now displayed as shown in Fig. 147.
Enter the thickness of the absorber in the Length field at the bottom of the Table section of the sidebar. This is important because the attenuation in the database is normalized to 1 cm, and the thickness of the actual sample is entered in the attenuation dialog.
Fig. 150. External
Attenuation Sidebar.
Click the Description button to add a description to the file (see Fig. 151). This is used to label the files and is copied into the spectrum file for added verification of results.
Manual Calculation
In the manual mode, you enter the values. In the Linear Attenuation section at the top of the sidebar, enter the Ref Rate (no absorber), the Cur Rate (with absorber), and the energy, then
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click Enter. The Ratio (correction factor) will be displayed above the Ref Rate field and in the
Attenuation Table.
NOTE
The Ref Rate must always be greater than the Cur Rate.
Enter the thickness of the absorber in the Length field at the bottom of the Table section of the sidebar. This is important because the attenuation in the database is normalized to 1 cm, and the thickness of the actual sample is entered in the attenuation dialog.
Fig. 151. Attenuation Description.
Click the Description button to add a description to the file. This is used to label the files and is copied into the spectrum file for added verification of results.
Editing the External Attenuation Table
To remove an energy from the Attenuation Table window, select it with the mouse and click the sidebar’s Delete button. To change an energy, select it from the table with the mouse, go to the
Linear Attenuation section of the sidebar, change the values, and click Enter.
To save the current table, click the Save... button in the sidebar. Click Recall... to open a standard file-open to recall an existing table (which has the default extension
.ATT
).
The External Attenuation Sidebar’s Control Menu
Figure 152 shows the External Attenuation Sidebar’s control menu
(which opens when you click the title bar icon). To edit an existing file in a Notepad-like editor, click Edit File.... This opens a standard file-open dialog to select the file, then an ASCII editor screen showing the file contents. Any changes made will be saved to the file.
The formatting does not have to be exactly as shown.
Fig. 152.
The Destroy selection erases all the values and energies in the currently displayed table. It does not alter the disk file (if any) unless the current table is then saved with the same filename. Restore will undo any changes made to the current table, including
Destroy, as long as it is used before the External Attenuation Sidebar is closed.
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