[Ohishi, Yuzurihara, Michimura; Kambara, Miyo, Ueno, Kokeyama, Aso, Kawamura with helps from all the people around]

X arm beam got back to the BS chamber. Right after that, we could see the beam at REFL port.

What we did:
 1. Swept ETMX randomly with coils and found the signal at BS PD (klog #1022). The misalignment was just roughly -90 urad in pitch, -90 urad in yaw after superb initial alignment by Miyoki-san et al (klog #1034).

 2. Centered the ETMX oplev QPD, zeroed coil offsets, and restored the alignment with picomotors.

 3. Fine adjusted ETMX alignment with picomotors for few urads. During this adjustment, we turned down the PD gain to be 70dB to 50 dB.

 4. After alignement, we got ~3000 counts at max which corresponds to ~30 uW. Since the BS PD is clipping the main beam and the aprerture of the PD is 9.8 mm dia, we should get more at REFL port.

 5. Checked the beam at AS port and could see the X arm returning beam with an IR card.

 6. Checked the beam at REFL port and could see the X arm returnning beam with an IR card.

Attached plot:
  Attached plot show the output of the BS PD (in blue). When ETMX is mis-aligned, the signal dissapear with background of ~50 counts. This tells you that the signal is actually from ETMX.

Next:
  1. Remove BS PD
  2. Set up REFL optics
  3. Measure power at REFL port