Alexa, Sheila, Daniel, Keita, Kiwamu, Stefan

We tried to lock the x-arm today, but we stumbled over a couple of mysteries.

- For the initial alignment we first pointed TMS onto ITM baffle PD1, and found TMS PIT=107, YAW=-207. This was -2urad, -4urad less in PIT, YAW than the previous alignment measurements (alog 9126), so we subtracted these values from the subsequent ones. We repeated this for the ITM using the ETM baffle PD. The ITM was PIT=57, YAW=-78.

- With both optics aligned we get about 18000 counts on REFL_B_LF. Surprisingly though, misalignment of ITMX (yes ITM) dropped this to 12000 counts

- We do get a PDH signal of about 5V out of the Imon demod. However, with the cavity just slightly misaligned, we still get a sinusoidal PDH signal of about 2V. We are not sure why, but are afraid it could be some scattered light.

- The PDH loop does lock temporarily, but the arm motion was slightly too large -- the sus pro-team is working on this.

- Next we misaligned PR3 in yaw by -150urad (from -272urad to -422urad). This put the straight through beam nicely on the Swiss cheese baffle.

- We also noticed a ghost beam to the right of the straight shot. It moves with ITMX and CPX, which pretty much nails down what it is.

- There is also a 2nd copy of the straight though and ghost beam visible to the left of the POP hole in the Swiss cheese baffle.