SudarshanK, PaulM

Summary:

We moved the Pcal beam spot on EndX by about 8 mm in y direction such that the beams are close towards the center of the optic from their optimal position of +/- 111.6 mm.

Details:

We moved the inner (top beam) using the last steering mirror on the Tx module  and moving the mirror mount screw clockwise in pitch. We were able to get the Pcal beam close to our desire location with about a quarter turn of the screw. The beam came out on the receiver side without clipping in vacuum but the receiver side optics had to be adjusted to get the beam into the RxPD.

For outer beam (bottom beam) we moved the beam by moving the mirror mount clockwise in yaw. We were not able to get the entire beam out of the vacuum when Pcal beam was moved to the desired position. We have no way of knowing if the clipping is happening on the way to the ETM or the way out from the ETM. We didn't feel comfortable (on Rick's advice) to translate the beam to relieve the clipping. We are hoping the beam is clipped on the way out and we can use the TxPD signal to calibrate the displacement. We will be able to figure this out once we have a locked interferometer by comparing the displacement measured by the interferometer and predicted by the Pcal photodetectors (TxPD in this case).

This new Pcal beam position will introduce a calibration error on hardware injection at a level of 2% at 2 kHz  and much smaller at lower frequencies. However, if the clipping is happening on the way to the ETM this will introduce significant error not only on hardware injection but the study that I am trying to do so we will have to come up with a plan to relieve the clipping.

The position of the Pcal beam spot before and after are as follows:

Also, the injection of high frequency lines are scheduled using the Guardian as described in alog 37765. The frequencies we will be running are: [5001.3, 4751.3, 4501.3, 4251.3, 4001.3, 3501.3, 3001.3, 2001.3]