Difference between revisions of "SBS HARP scan"
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Revision as of 09:00, 16 June 2021
Description
The purpose of the harp scans is to verify the operation of the scanners with beam on. Additionally, it confirms an acceptablebeam profile. Ideally, we need σ = 100–500 μm on both the IHA1H04A and IHA1H04B harps. If σx or σy is larger than 750μm (or less than 100 μm), ask MCC to try and improve the beam focus to be closer than our required specification. If ittakes more than 30 minutes, contact the Run Coordinator for advice.
Setup
- Beam current: 5 μA (tune beam)
- Target: No target
- Raster: Turned OFF
Procedure
- Verify the raster is OFF
- Ask MCC for harp scans with IHA1H04A and IHA1H04B, and to post the results to the HALOG.
- Verify the beam profile
- Find the harp scans on the HALOG; they should have titles along the lines of HarpFitter: 1HA1H04A and HarpFitter: 1HA1H04B
- For both scans, check if the fit is good. For example, a bad fit is shown in the figure below.
- If a bad fit is seen, you need to perform the fit manually:
- In a terminal, type jmenu; this brings up a GUI
- Search for harp fitter and click on the Harp Fitter Tool (HFT)
- On the HFT, click Modify Fit Parameters. A GUI called Expert Constants will pop up. Change exclude points on whichever peak you are trying to fit.
- After the changes, re-fit the peak by clicking on the corresponding Re-Fit button. Iterate as necessary to achieve a good fit to the data.
Special Procedures
Only perform these steps if requested by the Run Coordinator
