Chien-Ming, Te-Hui, Hsun-Chung, Michael

We remembered that the OPO cavity was redesigned to have the input mirror on the right side rather than the left side. The green SHG fiber output was reversed as a result, pointing towards the door.

Two of the mirrors were fixed at the wrong orientation, with the wedge pointing vertical rather than horizontal. This would cause beams to be deflected up and down. Since the screw holes for the custom mirror mounts are only oriented for the horizontal direction, we had to glue them again. With permission of Takahashi-san I took Cosmotec VE-22 vac seal from the TAMA South End dessicator. We then glued the mirrors in the correct orientation.

I practiced a bit my First Contact technique on a laser line mirror. We peeled First Contact from one face of the OPO successfully, but for the other one the tab came unstuck before the polymer, so I had to reapply and properly soak the tab. The four OPO cavity mirrors also have First Contact applied.

We could see the alignment of the green beam inside the OPO using spare mirrors.

Te-Huei told me about the operation of the homodyne detector. It is somewhat based on Advanced LIGO design. We can as for TAMA separately monitor AC (10-10000 Hz) and DC output. Instead of SUM out we can monitor each PD directly. We also have some test diagnostics for the resonant frequency of the PD circuit. The one currently mounted has some spurious resonance at 20 kHz in the noise spectrum. There is a spare homodyne which doesn't seem to have this resonance if it is in contact with the optical table. The black coating on the case of the spare was ground off near the screws which apparently makes it better (I don't know why). The spare one doesn't have high quantum efficiency PDs installed, but according to Chien-Ming we can just easily remove and replace between the two.

The old TAMA spectrum analyzer seems to have some plastic film peeling off of the back of the screen, which causes it to be hard to view. Maybe this was caused by some temperature difference during the period the ATC room was not air conditioned?