Performing MCA and EXAFS experiments


Choose the atom type

  • Enter in the XAFS experiments mode by clicking the [XAFS] tab.

    Choose the atom which might be in the crystal from the pulldown menu of the >Atom< section.
    (or eventually choose from the [Periodic Table...].)

MCA

Please note that the initial value is derived from the output of the boxes for the Wavelength, the Attenuator, and the Range after selecting the fluorescent atom. Start of the MCA experiment and optimization of the experimental conditions.

  1. Start the measurement by clicking the [Start] button of the [MCA] tab.

  2. As a consequence, the experimental mode changes to "XAFS Measurement", and the measurement will start automatically after a couple of minutes.
    When the selected atom can be detected in the sample, the output MCA graph represents two peaks. (Left-side: X-ray fluorescence; Right-side: dispersion of the incident X-rays.)

  3. If necessary, you can stop the measurements by using the [Stop] button.

  4. When the peak of X-ray fluorescence is not within the gray shaded area on the graph:
    - at first, check the Lower (or Upper) radio button;
    - next, drag the blue (or red) vertical line, and move it to the starting point of X-rays fluorescence.
    In the case both peaks overlap each other, select the minimum concave point between the X-ray fluorescence and the dispersion of incident X-ray curves.


SCAN

As a second step, this part will scan the X-ray fluorescence energy change by the incident X-rays.
Important notice!!
This program sometimes looks like freezing. The reason is that it automatically moves to the [CHOOCH] tab, followed by automatic calculation of the peak, edge, remoteL, and remoteH positions once the scan is finished.

  1. To proceed, select the [SCAN] tab, and then click the [Start] button with default values already inputed the box. These values are coming from the previous MCA step.

    The graph is an example when the selected atom is present within the crystal.

  2. It is possible to enlarge the gray zone by clicking the [Zoom In] button (lower-left part of the plot).
    You should then check that the change of energy intensity near the absorption edge is within the range of the enlarged graph .

  3. When the plot of energy range is not within the gray area, you can change the measurement range by playing with the [Advanced ...] option.


CHOOCH

  1. After the [SCAN] process is finished, the program automatically move to the [CHOOCH] tab. Please note that the values of peak and edge are shown on the left-side.


  2. You can enlarge the gray area by clicking the [Zoom In] button (lower-left part of the plot). The principle is the same as for the [SCAN] tab.
    The value of Edge (or Peak) can be changed by moving the vertical lines on the display, after selecting the corresponding check boxes at the bottom of the graph (Peak / Edge).

  3. By clicking the [Confirm] button, the results calculated by [CHOOCH] are copied into the [Submit] sub-tab of the [Collect] tab.
    As a rule, the value for the RemoteH is calculated by energy conversion: +200 eV from the Peak position. Similarly, the RemoteL value corresponds at: -50 eV from the Peak position.

Data Backup

MCA, SCAN, and CHOOCH results are saved automatically into a reserved directory designated by the file manager ([Special]-[Files/Directories name]). The files have the "xfs" extensions that can be read under Microsoft Excel or any similar calculation software.



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