Inside the hutch:
- If not using a FOILVERT reference foil, switch to the new reference foil (usually placed in holder in front of I2 ion chamber, sometimes placed in a scatter holder before I0. Both will show signal on the I2 display if signal cable attached correctly.)
- Make sure there are no samples or holders blocking the beam path through to I2. If using the scatter reference: you can calibrate without opening the sample shutter, which would enable samples to stay in place without risk of beam exposure with some specific adjustments (close shutter and take off computer control, but remember to put shutter back on computer control afterwards).
Turn the beam back on (Search the hutch). (If remote, you will need to ask staff to do this for you)
On WebXAS:
Rough Calibration
- If using FOILVERT, select the reference you want from the dropdown menu in the Data Collector window. It will ask you if you want to move there, affirm and the motor will move to the correct slot.
- Open the beam shutter.
- In the mono controls, move the mono towards the edge of interest and watch the signal on I2. If running remotely with WebXAS, it helps to have two windows open and viewable, one with the Data Collector window, the other with the "Monitor" window. You are looking for where the I2 signal drops with respect to the mono energy (or increases, depending on the direction you are approaching the edge from). When you find this energy (this is a rough calibration), go to “Calibrate” on the Mono controls and set that energy to the known/book edge energy.
Tune/Detune
- Move MONO to (desired edge energy + 1000 eV).
- In XASUTILS window, select the “Mono Tuning” tab. Move the tuning in one direction or the other while monitoring I0 signal, until you reach a maximum in I0.
- BL 7-3 does not run with a harmonic rejection mirror. As a result, there is no cut-off setting, and all harmonic rejection occurs via detuning the mono crystals.
- Depending on what element you will scan, you will want to "Detune" with the UP arrow. eg: If running Mn or Fe, detuning to 50% of the max signal on I0 is a reasonable way to run.
- If at higher energies, you can opt to detune less, and at lower energies, you may want to detune more.
Table Scan
- Close S1VGAP to 1.0 mm and S1HGAP to 6.0 mm.
- Scan TABLEVERT motor while looking at I0 signal. Scan +/- 2.5 mm, with 0.2 mm point spacing (Or use "rel2_5" align region from drop down). After scan, click on the maximum of I0 and "Accept position" to move TABLEVERT motor to this position.
- Scan TABLEHORZ motor while looking at I0 signal. Scan +/- 2.5 mm, with 0.2 mm point spacing (Or use "rel2_5" align region from drop down). After scan, click on the maximum of I0 and "Accept position" to move TABLEHORZ motor to this position.
Gains / Offsets
- Check ion chamber gains while you are at edge energy + 1000 eV (Ion Chambers tab in XAS UTILS). Make sure that the signal you read on the ion chambers is > 0.5 and < 4
- Move the MONO below the edge energy where I2 signal will reach its max. Check again that the signal you read on the ion chambers is > 0.5 and < 4.
- After changing gains, check offsets by closing beam shutter. You want the ion chamber signal to be a positive number which is as close to zero as possible. Adjust the offsets in the Ion Chambers tab.
- After changing offsets, collect offsets on the detector file you plan to use.
Take Calibration Scan and Calibrate
- Run the default queue with a region made for calibration scan at that edge. If you do not have one, you can use the "Region Wizard" to create a "Foil" region.
- Open plotter and plot the LOG(I1/I2)
- When the sweep is complete, while still in the plotter window- click “Modify” and then “Derivative”
- Copy the highlighted value for energy (autoselected by the plotter in the list of energies)
- In the Mono controls:
- Send the Mono to the copied value from the derivative
- In the Calibrate tab: Set to the known/book value.
Now you are able to move on with loading and aligning samples, windowing the detector (if using the 30 Element Ge detector), and running measurements!
NOTES:
- If you were using a filter with the soller slits for a previous edge, you will need to remove this or swap it out for the relevant filter for the edge you have changed to. This would be Z-1 from the element you are wanting to run (ex: Cr filter when scanning the Mn edge, Mn filter when scanning the Fe edge, etc.).
- If you need to change the crystal set for this edge change (go from Phi=0 to Phi=90 or the reverse), coordinate with the beam line scientists to make sure this can happen when they are present.