MAXRAY CALIBRATION
Position the spectrometer to element’s theoretical energy location via the element scan. If this is a new
crystal point set get the new Bragg angle from the WDS calculator in step 6, and setup a new crystal
set point by using the offsets of the closest bragg angle for that diffractor.
Under the service menu select diffractor scan and setup a range around the theoretical peak location.
(Note the lower the 2d spacing the wider range that will be required). The range and 2d spacing can be
found under the settings configuration. The program after a scan will display the centroid of the peak.
Now perform a smaller scan and lower step size (must have a defined peak). This is to insure proper
centroid location. Make a note this location and write it down this will be used later to step up the
correct offsets. Close the diffractor scan window
In the send command window do an energy = to the location in the previous step.
Under the service menu open up a detector scan window (the lower the 2d spacing larger the scan that
is required, for Copper it may be as high as +/- 3keV and for Carbon as low as +/- 50 eV). Usually only
one scan is required for the detector scan. Make a note this location and write it down.
Now calculate the diffractor and detector offset. Open the WDS calculator program if there is no
shortcut it can be found under c:\NORAN\eds\bin\calc.exe.
In the WDS calculator enter in the Crystal 2d Spacing for the diffractor the Theoretical Peak Energy
and the Measured Peak Energy from step 3 this is the offset for the diffractor. Select the Compute the
Calibration Offset. Make a note of the Theoretical bragg angle this be automatically calculated along
with the offset value (write it down).
In the WDS calculator enter in the Measured Peak energy from step 5 this is the detector offset. Write
it down.
If there is crystal set point for that Bragg angle add the offsets to the previous values enter in the the
calib.txt file. You must remove the original crystal set via the send command. The Bragg angle must be
enter to have the crystal point set removed.
In the send command window select the Crystal X Point Set (X being the diffractor number that has
just been calibrated). NOTE in the configuration under settings the first diffractor is 1 that would be
crystal 0 in the calibration file and so on….
Enter in the bragg angle, the diffractor offset and the detector offset. There are spaces in between all
numbers. Use the complete value given in the WDS calculator. If number is negative put a – in front of
the offset and send it to the controller.
Save the crystal point set by scrolling down in the send command window and select save calibration.
This will write to the floppy diskette in the controller.
Perform an element scan on the element that was just calibrated. Verify the peak location matches the
theoretical peak energy. NOTE within +/- 2eV for the light elements and 5eV for the heavier
elements
This should be performed on all diffractors. The LiF should have three points calibrated (Copper, Iron
and Titanium). The PET should have two points calibrated (Silicon and Titanium). Note the second
and three points may require several runs to get the location correct. This is do to the fact the software
will try to calculate an offset from the nearest bragg angle calibration point. Note this can be done on
as many elements that are required by the customer.
If the counts are low the turret scan should be run to verify the angle of the diffactor. One caution on
changing the crystal angle on wide range diffactors this may effect counts on the extreme ends. Set the
spectrometer to the peak location via Setting Position Spectrometer. Perform a turret scan. This is
under Servicesturret scan. If the turret position is off the crystal.txt file will have to be modified. Do
this by removing the floppy diskette from the controller open a notepad window open the floppy
drive and select crystal.txt file locate the crystal and edit the position, and then save it. Close the
Maxray program. Place the floppy diskette back in the controller and reboot the controller. Note
usually if the turret position is off for one the others will be off but please run a turret scan on all
diffractors.