Aritomi, Marc

Following the discovery of the not fixed lens on the IR path, we started to realign this beam.

First, I fixed by hand this lens at a position where the AC signal with the surface reference sample was ~0.08 (to compare to the previous ~0.25 and expected 0.36).

Then, we made sure the beam was horizontal after the 2 lenses using the pinhole at 45 and 27 mm on Z.

This allowed us to measure the beam power transmitted by the pinhole at various Z position.

From this measurement, it was possible to extract the waist size (~70um ) and position (~34 mm).

I took 2 points for the red beam to find the crossing point of these 2 beams.

And it can be seen (fig 1) that the ir beam has to be shifted horizontally by 232 um to have the crossing point at the the ir waist.

I started to move the ir beam using again the pinhole at 2 positions but it was required to move this beam both horizontally and vertically.

I'll finish this alignment this morning.

Note that compared to the previous situation, the crossing point is 3 mm closer towards the periscope.