[Aidan,TJ,Nutsinee]

Following the HWSY lens replacement during last week's mini-vent, we have been working to recover the alignment of both HWS beams. Without the ALS beams, this is accomplished using the more laborious method of injecting the HWS beams into the vacuum system, close to centered on the in-vacuum lens, and swinging SR3 around in PITCH and YAW. The return power on the HWS CCDs is plotted as a function of position and yaw. This technique relies on the ITMs being properly aligned.

HWSX

We received no return beam from ITMX in any portion of the PIT and YAW phase space. We concluded that, given the HEPI lock down and ITMX activity last week, ITMX has not returned to the same alignment that it had before the vent. Without access to the ALS beams or the optical levers, it was difficult to make any progress on HWS alignment until the ITMX alignment is corrected. The HWSX alignment effort is on hold until ITMX is fixed.

HWSY

After locating three regions in SR3 angular phase space that held a total of four return beams, we identified which belonged to the ITMY HR surface by running a ring heater test and observing the expected thermal lens (in agreement with the online simulation).

We had to fold the HWSY layout to lengthen the distance from the last lens to the HWSY CCD such that the latter could be placed at the image plane of ITMY. We added an additional optic and moved the HWS CCD as shown in the attached images. The return beam looked much cleaner and the main BS EQ stops look much sharper (less diffraction).

The current status is that the HWSY camera is running WITHOUT the Hartmann plate installed but WITH the bandpass filter installed. The HWSY CCD is currently attached to the HWSX computer (H1HWSMSR) instead of HWSX. This is a temporary measure until the HWSY computer (H1HWSMSR1) is functioning correctly.

Before:

After:

HWSY return beam - misaligned to show the EQ stops.