SNRLXRF Installation and Users Guide
(S. Sutton, Dec. 2000)
Launching the IDL user interface
Overview of the SNRLXRF Interface
Major Element Composition and Thickness
NRLXRF (Criss 1977) is a Fortran program written for conventional XRF analyses where one has a standard for every element of interest. Trace element standards with micrometer scale homogeneity are rare. The modified version of NRLXRF used here is designed for “standard-less” analysis of XRF spectra obtained with monochromatic radiation. The standard-less approach is to use an internal reference element, i.e., concentration of one element in the spectrum is known independently (stoichiometry, EMP analysis, etc.), and compute relative sensitivities using the prediction capabilities of NRLXRF. An IDL interface called snrlxrf.pro has been written to provide an easy user interface to the NRLXRF program. This document describes the use of the Windows version of this software.
The package consists of the following files:
nrlxrf.exe |
executable version of NRLXRF |
snrlxrf.pro |
IDL user interface to NRLXRF |
nrl_init.pro |
structure definitions |
run_nrl.inp |
command file used during NRLXRF execution |
run_nrl.bat |
batch file used in executing NRLXRF |
mono.dat |
input file with incident energy data generated by snrlxrf.pro |
comp_file.dat |
list of user defined major element compositions |
xrdat2.dat |
input file containing NRLXRF commands generated by snrlxrf.pro |
xrdat3.dat |
additional input file (typically not used) |
xrdat4.dat |
additional input file (typically not used) |
xrdatc.dat |
list of compositions of frequently used compounds |
xrdatp.dat |
data file containing fundamental x-ray data (not to be user modified) |
Place all the above files in a single folder.
Define a new system environment variable NRLXRF_DIR to be the folder containing these files (access environment variable definitions through the system control panel)
Give all users write permission to this folder.
Launching the IDL user interface
Add the NRLXRF folder to the IDL path through the IDL preferences
At the IDL prompt, type "snrlxrf"
Overview of the SNRLXRF Interface
(Click on a particular widget to go directly to its description.)
NRLXRF has two modes: Analyze and Predict. Use the former
to compute concentrations based on peak areas. Use the latter to predict
the relative sensitivities for specific fluorescence lines. Type in the
relevant incident beam energy (monochromatic). In this and all editable
fields, the ENTER key on your keyboard must be struck for the change to take
effect. A 45 degree in/ 45 degree out analysis geometry is hardwired into
the program but other geometries are possible (consult your local SNRLXRF
expert). Return to Graphic
NRLXRF allows use of an incident beam filter but such filters are irrelevant for the monochromatic/relative sensitivity approach used here. The detector filtering is important because relative sensitivities can be affected by absorption through these materials. Three filters can be defined. For each of the 3, the user can select one of the built-in choices, or, by selecting "Other", enter an element of choice in the adjacent editable field. Also enter the density and thickness of each filter. Zero, 1, 2 or 3 detector filters may be used. Return to Graphic
Major Element Composition and Thickness
The user must define the major element composition and thickness of the sample to allow NRLXRF to make absorption, secondary fluorescence, etc. corrections. As for filters, the user can chose one of the built-in materials from the droplist or define a completely new material through the "Composition Editing Fields" (see below). When a built-in material is selected, the density and major element composition are displayed (the former in the adjacent editable field; the latter in the "Element List" field). Three "types" of samples are available via the droplist: Homogeneous, Separate and Particulate. Homogeneous, the typical selection, assumes the sample is a homogeneous parallel-plate. Separate assumes the sample consists of separated particles (implementation not fully tested). Particulate assumes the sample consists of densely-packed particles such that shadowing is significant (not implemented in current release). Return to Graphic
Shows the current composition defined for the sample. Elements listed as "Fixed" are unaltered during the analysis whereas those listed as "Unknown" are optimized. All "unknown" elements are given an initial (seed) concentration of 0.1 wt % but these can be changed through the "Composition Editing Fields" (see below). Self-explanatory buttons to the left also allow these entries to be modified. Return to Graphic
Allows modification of the compositions shown in the "Element List" field. Element symbol, concentration and optimization parameter can be modified by selecting the appropriate entry in the Element List. Remember to use the Enter key on your keyboard after making changes. Return to Graphic
Press the "Clear all elements" button then make new definitions using the "Add new element" button. Use the "Edit COMP. NAME >" button to give the material a name then press the "NAME and SAVE this composition" button. The new material will now appear in the Major Element Composition droplist in this and subsequent sessions. Return to Graphic
This routine is designed to be used on fluorescence peak area files generated by M. Rivers EPICS MCA program or his VMS routine called fit_spect.pro. Choose the appropriate Peak File Type through the droplist. To read in one of these files, press the "READ A PEAK FITS FILE" button. A dialog box will appear to allow you to navigate to the file of interest. Such files typically contain multiple spectra fits and these will appear in the adjacent field. The process of selecting a particular fit causes the net peak areas of ALL fitted peaks in that fit to appear in the "Peak List" field. Return to Graphic
Select the specific peaks which will be used for the concentration calculations (typically the K alpha and L alpha peaks). Use the Windows mouse features, shift left button and ctrl left button to make multiple selections. All element selected in this way will be added to the Element List unless they already exist there. Also, "Unknown" is the default but again this can be changed via the modification fields above. Return to Graphic
You must select one fluorescence peak which will be treated as the internal reference element. Type this peak name (Ca Ka, Fe Ka, Pb La1, etc.) in the editable field (hit Enter). Important Note: This peak must occur in the Peak List and that element must appear as a Fixed entry in the Element List!! Return to Graphic
These widgets allow you to control where the composition results are written. The file name is sequenced but this can be manually overwritten via the editable field. Return to Graphic
Once you're happy with all the settings, hit the "Run SNRLXRF" button. A text window will appear containing the results. One of the nice features of this interface is the ease of repeating the calculations - simply make any desired changes and hit the run button again. Return to Graphic
Each time an event occurs in the interface screen (e.g., button push, droplist selection), the procedure structures are written to a file called snrlxrf.sav in the user's default directory. Each time SNRLXRF is launched it will restore values from this file if it exists. This makes it easy to begin a new session with the previous settings intact. Return to Graphic
Click here to view a sample output from SNRLXRF. The computed concentrations (wt %) are at the end of these files. Element concentrations fixed during the optimization are so indicated.
COMPONENT
AMOUNT IMPREC.
BIAS
ADJUSTED
SI 70.00000
(FIXED)
70.00000
C
30.00000 (FIXED)
30.00000
TI
0.1101385 +/-0.0011014 +0.0000000
0.110
V
0.0113847 +/-0.0001138 +0.0000000
0.0113847
CR
0.0235369 +/-0.0002354 +0.0000000
0.0235369
MN
0.0102146 +/-0.0001021 +0.0000000
0.0102146
FE
0.0096415 +/-0.0000964 -0.0000000
0.0096415
W
0.0568666 +/-0.0005687 -0.0000000
0.0568666
SR
0.0002410 +/-0.0000024 -0.0000000
0.0002410
Y
0.0036567 +/-0.0000366 +0.0000000
0.0036567
ZR
0.0065216 +/-0.0000652 -0.0000000
0.0065216
(TOTAL) 100.2322006
+/-0.0012768 +0.0000000
100.232
This page was last updated on December 11, 2000