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- Set up an aluminum core tray to hold the unwrapped section half (you will wrap it with Ultralene Ultralene® later, but GLAD® Plastic Wrap is thick enough to interfere with measurements). Place the core tray far enough back from the edge of the bench that the pXRF will be several feet away from the operator.
- Put a long ruler next to the aluminum tray to measure the measurement offset.
- Place the docking station to the side of the core tray.
- Collect the rubber lead impregnated shield. Place a plastic window in the dedicated area and measure the offset. The point at the intersection of the blue lines is the offset (Figure 13).
- When it is time to take a measurement the pXRF will lock in to the mat as shown in Figure 14.
Figure 13. Measuring the offset. A. Lead mat with offset window. B. Offset window (crossing point of the blue lines is the offset)
Figure 1314. pXRF being lowered into section half shielding. pXRF oriented with indents facing set screws.
Again, please note that it will be necessary to cover the core surface with Ultralene® film and GLAD® Plastic Wrap in order to protect the nose of the instrument and the underside of the shield from contamination. See Preparing Section Halves, below.
Important! Do not measure the core section half without covering it with film!
INFORMATION TO UPDATE: Note for tech: section half: sediment vs. hard rock it seems that the section half prep described above is for sediment. Double-check. write a paragraph for hard rock prep. In College Station: film not used for hard rock sections (core surface is cleaned before measurement).
Sample Preparation
Sample preparation is split into two main categories: discrete samples and section halves.
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To create a discrete XRF sample, assemble the following components as shown in Figure 1415, below:
- Powdered & dried sample
- Scoopula
- XRF sample cups (32 mm Double Open Ended)
- SPEX Ultralene Ultralene® thin film (0.16 mil; 4 µm thick)
- Whatman Filter Paper Circles (32mm) or Parafilm M® film
- Foam plug
Figure 1415. Mortar and pestle along with scoopula. XRF Sample Cup components denoted with red arrows A. Open-end Ring B. Cup C. Cap D. Ultralene® film box E. Whatman Filter Paper F. Foam plug inserts
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3. Next place a barrier layer on top of the powder, either Whatman Filter Paper or ParafilmParafilm®. This creates a seal that prevents contamination and keeps powder secured in place. Take a piece of Whatman filter paper and put it on the powder or cut a square of parafilm, wrap it over the end of the foam plug and put inside the cup. Press down evenly until it is firmly on the powder.
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Note: When using the Flex Stand, it is possible to perform the Cal Check by simply placing a stainless steel disk on the instrument nose and closing the lid of the Flex Stand. An extra stainless steel disk can be found in the pXRF supplies.
Figure 20. Performing a Calibration Check. A. CalCheck Button B. Indicator Bar C. Disabled ‘Start’ button
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Choose either the Geochemical or the Soil Mode; each one has specific scanning parameters, and preferentially scans certain elements. Discuss with scientists which mode is preferred.
Note: Once a mode is selected, it does not have to be re-chosen before each measurement or when the gun is turned on/off.
Click on Mode, located top right in Figure 21 (arrow A). On the left hand panel, you can choose between Geochemistry and Soil modes (Figure 21, B). Click on each to see the elements scanned and the beam conditions used in each mode.
Figure 21. Mode window. A. 'Mode' tab B. Measuring Mode options. Elements and beam information for Geochem (on the left) and Soil (on the right) modes
Selecting Measuring Time
Establish Establish the measuring time for each beam. To access this, click the Set Up button at the top of the screen as shown in Figure 22, arrow A, below. On the left hand panel, click Test Condition. This will show the minimum (Beam # Min) and maximum (Beam # Max) time currently set for each beam. Adjust the settings as desired in seconds and click Save.
Note: Check to make sure the Spectrum files are set to one spectrum output for each reading, not an averaged spectrum file. You can verify a spectrum file was created for each run by seeing a spectrum graph in the results window.
Figure 22. Innov-X Set Up Screen. A. Set Up tab B. Test Condition button C. Test Time area D. Save button
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