TJ, Camilla. WP #11483.
Uninstalled the "new" S&K HWS laser (TSOP M1900163) from the ALS table, stored it in it's case in the LVEA TCS cabinets. Removed fiber and fiber launcher. This was installed in 62089.
Reinstalled the "old" diode source M530F2 (eye safe). Using M92L02 20um multi-mode fiber and original D1800125 fiber launcher. Reduced length of the tube of D1800125 fiber launcher as we thought we need to bring the F=125mm lens closer to the launcher.
Realigned the path to get a retro-reflected beam off ETMX and checked this by mis-aligning ETMX. Took new references on EX, and ITMs at 00:08UTC.
Photos before and after attached. Decision made to swap back to original source in T2300336. Will update FRS 14310 with Aidan.
We are getting data, see attached, but the TOTAL_PIXEL_VALUE is changing as we thermalize, which we don't want. There is some clipping happening which we can work to minimize on table.
TJ and I repeated the laser swap EY 73878 but struggled to get an unclipped beam. We went back to EX ~3pm Oct 31st to understand if the EX beam was clipping somewhere to get the bad HWS data above. We saw the beam was clipping on the edges of BS2 and M2 and then after clipping L1 (1" optic), the beam appears round again. Layout D1800270.
In 42171 and T1000717 there is mode matching solutions of this path showing the beam should remain under 10mm diameter until the Transmon telescope. We don't remember this ever being the case. The beam starts around 10mm and then diverges to >1" after L3, rather than converging.
We think we should revisit this mode matching to understand what our input optics should be and check all the lenses are correct (they are labeled as in D1800270).