[Alexa, JoeG, Paul, Kiwamu]

 Today we mainly installed the optics on the west side (which is close to ISCT1) in HAM1 and placed all the optics in the west side except for the in-vac POP PD.

The REFL AIR path is aligned. We didn't align the POP/ALS path because we didn't have green light or bright POP beam at the moment. As for the in-vac REFL detector path we placed only M2. We will install the rest of them on the east side tomorrow.

Below are notes for some particular sections of the west side :

Beam Diverter 1 :

We had to rotate the beam diverter #1 (BVD1) by 180 deg. The beam diverter has a couple of small PEEK materials on the mirror holder and they were initially on the side where the REFL beam hits. So we wanted to avoid this. Since there is no PEEK materials on the other side of the holder we simply rotated the whole structure by 180 deg. Of course we also flipped the mirror itself such that its high reflection surface remains facing to the REFL beam. Note that the rotation of the actual BDV1 is now different from that in the layout drawing (LIGO-D1000313-v10) because of this modification.

REFL path :

Looking at M7, which we had installed before the HIFO started, we noticed that M7 was not at the place that the diagram showed (LIGO-D1000313-v10). It was too far from the west by 2" or so. But I remembered that the position of this mirror was adjusted to catch the REFL beam at its center. So we used this mirror as a reference to recover the good alignment of the IMs and PRM. After Paul untripped IM1-4, enabled the master switch of IM1-4 and set the alignment of PRM back to that in April, we got a decent alignment without a fine tuning.Checking the REFL beam on ISCT1 we confirmed the good alignment as the beam hit the REFL shutter trigger PD.

 We also checked the beam position on the view port on the HAM1/2 septum. It was well-centered. So regarding the REFL beam as a good reference we installed the relevant optics without touching the REFL beam pointing. So for the reason M7, M1, HW1 and M14 are off from the layout (LIGO-D1000313-v10) by about 2 inches or less toward the east. Finally M7 was repositioned because we added two beam splitters which can change the beam trace by non-negligible amount. Currently the REFL beam hits the center of the top periscope mirror on ISCT1. The beam is off somewhat on the bottom periscope mirror because we touched M7 but this is not a big deal because we can steer the top mirror.

M14 (a.k.a. pick off for high power beam dump):

M14, which had been a 50 % BS dedicated for HIFO (see LIGO-D1201390-v2), was replaced by a 90% S-pol BS (LIGO-E040512-B4 and also mentioned in Keita's alog #7844). The removed 50% BS is currently ln the clean booth nearby HAM1 in a bag labeled as "M14".