How to set up/modify a .throttle file in GeoPIXE

A .throttle file is used while collecting data to reduce the overall file size. The function of a .throttle file is to scale down the number of photons measured in very strong peaks. Instead of counting every photon for a strong peak (such as a scattering peak), you can use a .throttle file to tell the Maia detector to record only one photon for every 5, 10, or 20, (etc.) incident photons in a specific region of the spectrum. When GeoPIXE reads in the throttled data, it re-scales the throttled region of the spectra by the same throttling factor to restore the correct relative peak heights.

A throttle file is different from a .cuts file. The .cuts file is important when fitting data. The .throttle file is important when saving data, during your experiment at the beamline.

NOTE: This process should be completed in GeoPIXE, not Maia Control. Initiating throttling from the Maia Control Spectrum Display does not save the .throttle file properly.

Video

Steps

1. In the GeoPIXE Spectrum Display window, load or import spectra from the sample that needs throttling. This data usually comes from a short test XRF scan on your sample.

2. Go to Analyze > Throttle. This will open a window asking you to choose the energy range to throttle.

3. In the Spectrum Display, set the view markers around the region you would like to throttle. Or, enter the energy range values manually in the "Set Throttle in View" window.

4. Set the throttling factor for the peak.

5. Press "Throttle" to see the changes applied to the spectrum. Adjust the energy range and throttling factor until you are satisfied with the result. You can add more than one region to your throttle file if you set the view to a different region and press "Throttle" again.

6. When finished, press "Save Throttle spectrum." It's a good idea to put the beam energy and the name of the throttled peak in the filename.

7. To apply this .throttle file to your experiment, you will need to enable throttling and load this throttle file in Maia Control. CHESS staff will help with this step.

-- LouisaSmieska - 10 May 2016