Blue Team
We ramped up the effort to get the geen ALS WFS used for the One Arm Test on ISCT EX, to help us with the alignment-induced noise between red and green.
Here is where we stand at the moment:
- Electronics: mostly installed, see entry by Filiberto and Daniel
- WFSs + cables + patch panel: found, in the EX VEA
- Picomotors, breakout box and cables : found (breakout box already at EX), picomotors mirrors on Evan's desk
- New WFS layout designed by Jax and Evan: lenses, mirrors, beam splitters -- all in hand
- Cabling: Mostly done by Filiberto between the field rack and the remote rack; the cables between the optics table and the field rack need to be made - list sent to Filiberto
Plan for tomorrow/Friday (in parallel with Filiberto's work)
- Get new optics, WFS and picomotors on the table (when the green team is not working)
- Install patch panels and cables as they become available
- Update electronics drawings
- RCG model update
A quick outline of the proposed mode-matching solution:
We are working from D1100607. This is the layout for ISCTEY, but is (I am told) a pretty good description of the current state of ISCTEX (moreso than the ISCTEX document, anyway).
According to Sheila, mirror M16 is some sort of beamsplitter (labeled as 90/10, but measurements show more like 50/50). The transmission of M16 goes onto a high reflector, which then goes onto a QPD. This is meant to be temporary, and we intend to remove it when laying down the WFS. Apparently there is 6 mW going through M16. In order to get < 1 mW on the WFS, we will probably replace the high reflector with a 90/10 BS and a dump in transmission.
We will propagate the reflection of the 90/10 BS through a lens and then onto a 50/50 BS. The reflection of the 50/50 BS will go onto a picomotor-mounted high reflector, and then onto a WFS. The transmission of the 50/50 BS will then go onto two folding mirrors, then a picomotor-mounted high reflector, and then the other WFS (or maybe we will make one of the picomotor mirrors do double duty as a folding mirror).
An a la mode optimization plot is attached. The position of M16 is taken to be 0 m. The 200 µm waist at -0.41 m is taken from the ISCTEY document; there is no guarantee that it's actually there. alm says to place an f = 544 mm lens at 0.27 m. This gives a 400 µm waist at 1.35 m. The Rayleigh range is then 0.94 m. For optimal Gouy phase separation and spot size, we want to place each WFS one Rayleigh range away from the waist; i.e., one at 0.41 m and another at 2.29 m.
The spot size on each WFS should be 560 µm, giving a diameter of a little over 1 mm.