Fluorescence

The beamline experimental table is equipped with a fluorescence detector in order to obtain fluorescence measurements on the samples. Please check the site http://xdb.lbl.gov/ for characteristic K, L, andM x-ray line energies (emission)and electron binding energies (absorption).In order to produce the spectra, follow the procedure below:

1. Protect the x-ray detector from the direct beam with the proper shield.
2. Remove the X-Ray nozzle.
3. Set the fluorescence detector at 90 degrees with respect to the X-ray beam.
4. Switch on the fluorescence detector power supply.
5. Close the beamline slits after the monochromator (compulsory for high energy resolution).
6. Open the beamline (you probably need to reduce the photon flux).
7. Run the fluorescence control panel using the Fluorecence button on the XRD1 Control Panel window.
8. Select the channels number (default 4096) and the preset time (in seconds; 0 for continuous collection). You can load a raw calibration curve using the proper button. The curve matches the channel number with the energy, using - for the 4096 channels configuration - the following values: (Ch 1350->8041 eV), (Ch 2238->13375 eV), (Ch 2918->17443 eV). The files are called "calibration_4096_channels.dat" and "calibration_Linear.dat".
9. It is possible to run a element threshold scan using the monochromator panel, entering the initial and final channel number (use the mouse pointer to check the values on the graph).

If the florescence scan contains the edge of a known element, it is possible to use the edge energy value to calibrate the monochromator (a CHOOCH link will show suggested values). The procedure to calculate the offset between the actual and experimental values and consecutively modify the monochromator position/angle is reported below:

1. Using a browser, connect to the monochromator setup web page and type the password to access the calibration webpage.
2. Select the crystal you are working with.
3. Put in the experimentally fixed energy field the theoretical value of absorption for the used atomic edge [as example, 8.979 KeV for Copper].
4. Put in the actual monochromator energy the value you have found from the florescence scan (or any other method used) [as example, 8.994 for Copper].
5. Press the Calculate Offset button and Confirm the result if ok.
6. Use the BeamWatch utilities to call the INIT function for the XDIFF_mono element.