Fluorescence Scan

A critical step in performing a successful MAD experiment is the measurement and analysis of a fluorescence spectrum from the sample. The first step is to move the beamline energy to the region of interest. Open the hutch page and follow the directions for moving the energy, as follows:

On 22ID, move the beamline energy to 100 eV about the absorption edge of the metal of interest and optimize the beamline;

On 22BM, move the beamline energy to the absorption edge of the metal of interest and optimize the beamline.

Once the energy has been properly set and the beamline optimized, mount your sample and collect a single image (at the current energy) to verify that the system is properly aligned.

After you measure a diffraction image, open the MAD page (note that it is set up for a Se scan).

If the incorrect metal is shown in the edge setup section, press the Periodic Table button and select the correct metal. The metals shown in bold are within the operational envelope of the beamline. If the metal you are interested in is grayed out, then you cannot perform a MAD experiment at this beamline.

Fluorescence Detector: The detectors used for measuring the fluorescence signal have a fairly high linear dynamic range, but can be still be saturated. To verify that the detector will not be saturated during the fluorescence scan you can perform a 5-second test measurement by pressing the Test button in the Test Fluorescence section (bottom right hand corner of MAD page). After the Test button has been pushed, the values for I0, fluorescence, and ratio will update. The value in the fluorescence measurement should be kept below 200,000. If the fluorescence value is above 200,000, change the attenuation accordingly.

Once the proper attenuation has been set you are almost ready to collect you fluorescence data. The last step is to properly set your Output Directory. The default directory is your /home/user directory. If you want to take the raw data home, you will need to redirect the output directory to your /u#/yr_mo_day_user/ directory.

 Once you have set your output directory, collect your fluorescence data by pushing the Run Scan button in the Fluorescence Scan section of the page. The fluorescence scan should take about 1 minute to complete. After the scan is finished you will see a pop-up of the raw data; a typical Se scan is shown below.

The next step is to analyze the raw data. After the scan is completed, you will notice that the Input Filename field in the Analyze section will have updated to the name of your raw data. If you want to analyze an old data file, you can either manually enter the name or browse for the file. Once the proper filename has been set, pressing the Analyze Button will start the Benny-Chooch program, which when complete will pop up a results window similar to the one shown below.

This page will automatically print at the local beamline printer and will only stay open for a short period of time. The f’ and f’’ fields in the Analyze section will update to reflect the Benny-Chooch results. The energies defined for the Edge, Peak, and High Remote will automatically be downloaded to the Energy section of the Collect Strategy page.

You should be ready to collect your MAD data.

It is always a good idea to let your user support person know if you are going to perform a MAD data collection so that they can spend a little extra time during your beamline training to prepare you to work on your own.

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