BOZ (TZPG) alignment

  1. Defocus KB mirrors by sending both HFM and VFM benders to CW limit switches (largest position, close to 200 mm). This can take ~30 min, so plan ahead.

    ../_images/KB_defocused.png

    KB mirrors fully defocused (from elog 2078).

  2. Switch off all FFT LEDs to maximize the FDM camera sensitivity for low intense beams. This avoids using high GATT transmission on the zone plate unnecessarily. Look at the FEL (SA3 mono 1st or 2nd order) on pBN at the sample position, with typically 2 - 10% GATT transmission. The beam should look like this:

    ../_images/FEL_on_pBN_defocused.jpg

    1st order of FEL on pBN at the sample position with defocused KB mirrors, from elog 2497/36.

  3. In XFEL Synch and Share, open the document SCS > Instrument > PSI-Optics > TZPG.odp. Choose the desired TZPG from the last updated picture in the presentation.

  4. Move the TZPG stage into the beam. Rough positionning to find the right TZPG is indicated on the FFT_TZPG scene. A Point And Click device will simplify the rough positioning in the near future.

    ../_images/TZPG_scene.png

  5. With LED off for better sensitivity, locate the 3 diffracted beams on the pBN. They should appear above the defocused beam located earlier. At this point, a rough adjustment of the guard stage is possible to limit the exposition of the neighbouring TZPG. Final adjustment of the guard stage is done using the DSSC signal.

  6. Lower the GATT transmission to < 1% for DSSC. We need a lot more photon to see the beam on the pBN than we need to fully saturate the DSSC. If proper GATT is not known, find it by starting with very very low transmission and increasing step wise, looking at DSSC.

  7. With low GATT transmission, open the gate valve to the DSSC, let the beam go through the FSSS.

  8. Observe the signal on DSSC. It should look like this:

    ../_images/DSSC_BOZ.png

    DSSC signal from BOZ setup, from elog 2609/30. A gradient of intensity from left to right is observed. It may be a sign of non-homogeneous illumination of the BOZ.

  9. Move the zone plate to obtain homogeneous illumination.

  10. Close the guard stages to avoid overlap between ROIs on the DSSC.

  11. Save the TZPG position in the Store/Recall device (link on the FFT_TZPG scene).

  12. Go back to the pBN and mark the position of the beam with 3 rectangles on the pBN.

../_images/FEL_pBN_BOZ.png
  1. To save these ROIs, change the scene to design mode (top left button), right clik on the image widget and select ImageGraph: Properties > Set ROI and Aux, and save the Karabo project.
../_images/save_ROI.png

Example how to save the ROI and crosses on a scene for future reference.