TJ, Camilla. WP 11730 Table: D1800270
TJ and I swapped the EX HWS fiber from a M92L02 200um 0.22NA multi-mode fiber to a M14L01 50um 0.22NA fiber, the same that LLO successfully uses. This gave us a focus ~150mm after the 125mm lens, where D1800125 suggests our focus should be 1.25m from the launcher (or ~100mm from L2 62398). TJ found we need to change the spacers in the D1800125 launcher, from the design 12mm closer to 11mm to get the beam focus at 1.25m. We got a beam a much more sensible size by only securing the launcher on one side and could see a return beam off ETMX, image will be commented. We plan to buy/find more spacers before continuing this work.
LLO has recently been swapping 1" optics to 2" to reduce clipping 69891. We did this in 62995 and 73878 so have M1A, M1B and M1C on EX as 2" optics but currently no picomotors in the HWS path.
Attached image with the plate off. Looks much better than before in the size and uniformity, but it would need more alignment and focusing if we decide to stay near this launcher to lens length.
From March 19th. TJ, Gabriele, Camilla
On March 12th, TJ and I tried to change the length of spacers in D1800125 by 1mm increments. This still didn't give us the required beam size.
On March 19th, TJ, Gabriele and I measured the beam straight out of the fiber and SM05SMA adapter, before the spacers and f = 20.0 mm bi-convex collimating lens. We used a ruler for horizontal, put white laminated paper on a stand to see the beamsize and measured the diameter with calipers, as the beam is too large for beamscanner. Results attached. Plan to use this to make a mode matching solution.