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Update SOPHIE Alignment

watts
2024-05-02 15:37:15 +02:00
parent c0885d47b7
commit 8013416a6d
1 changed files with 9 additions and 2 deletions
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SOPHIE-Alignment.md

@@ -30,7 +30,7 @@ The SOPHIE endstation uses a novel interferometer design where:
| ![Interferometer_Schematic.svg](uploads/76677416d91bb6052882bbc0a687a685/Interferometer_Schematic.svg) |
|:--:|
| Figure 1. Schematic of the SOPHIE position-interferometer design. The red and blue lines are the two orthogonal linear polarisations of the laser beam and their reflections from the polarising beamsplitters (yellow) are offset to clarify the beam trajectories. The green objects are quarter-wave plates that rotate the beam polarisation by 45°. |
| Figure 1. Schematic of the SOPHIE position-interferometer design. The red and blue lines are the two orthogonal linear polarisations of the laser beam and their reflections from the polarising beamsplitters (yellow) are offset to clarify the beam trajectories. The green objects are quarter-wave plates that rotate the beam polarisation by 45°. The corner cube will always reflect the beams along a trajectory parallel to the incident beam, but with a small position offset (determined by how far the incidence point is from the central corner).|
| ![SOPHIE_interferometer](uploads/43bfb17f3f46e87154275bf1e8b9672b/SOPHIE_interferometer.png) |
|:--:|
@@ -59,11 +59,18 @@ Sensor1.zCorrectMatrix[1] = 0.0
7. Calculate the effective mirror tilts of the J and K interferometer reference mirrors.
8. Calculate the number of screw turns required to remove the calculated tilt from the reference mirrors.
If one is unable (or unwilling) to get the interferometer signal high enough to reliably lock after adjusting the reference mirrors, then the drift correction could instead be applied to the software zCorrectMatrix.
### Fix the Virtual Drift
Apply the calculated screw turns to make the reference mirror parallel and then further adjust the interferometer components to compensate the beam alignment and optimise the signal strength.
### Characterise and Fix the Real Drift (Requires X-rays)
1. Find an easily locatable feature that is also small and doesn't change in appearance very much when changing photon energy. A metal particle close to the corner of a membrane is ideal. Symmetry is often important.
2. Select a pair of photon energies that will give a significant difference in focal length (i.e. movement of the ZP-Z stage).
3. Measure the position of the object at each energy and note the change in position.
4. Rotate the endstation using the Girder Mover.
5. Optimise the X-Y position of the Girder Mover for maximum X-ray signal.
6. Iterate steps 3-5 until the drift is minimised.