We centerd the input of WFS QPD.
We found that the MC REFL image was no longer round and that the MCWFS DC quadrant spots were mostly
in one quadrant. So we re-centered the MCWFS beams in the following way:
1) We unlocked the MZ and adjusted the PZT voltage to keep the beam on the WFS from saturating.
2) Re-aligned the black hole beam dump to center its beam in its aperture.
3) centered the beam on the MCWFS optics and MCWFS QPD displays.
4) Relocked MC.
Below is the image of the IOO Strip tool. You can see that the MC REFL DC is now more flat. The
MC pointing has also been changed (see the MC TRANS HOR & VERT channels). The MC transmitted
light is also now more stable and higher.
We tried to center the QPD, and we found that there were a few hundred mV of dark offset for each
quadrant of QPD. We adjusted them with this scripts:
The power supply of a lock-in amp, which is on the Y-arm side of PSL clean room, was pulled out by my mistake.
Then I reconnected it, but I don't know whether it is re-adjusted properly.
I'm sorry about this. If you are using that amp, it should be checked.
On Monday evening, I ran this command: trianglewave C1:IOO-MC_REFL_OFFSET 0 4 120 600;ezcawrite C1:IOO-MC_REFL_OFFSET 1.76
trianglewave C1:IOO-MC_REFL_OFFSET 0 4 120 600;ezcawrite C1:IOO-MC_REFL_OFFSET 1.76
which I thought (from the syntax help) would move that offset slider with a period of 120 seconds for 600 seconds. In actuality, the last argument is the
run time in number of periods. So the offset slider has been changing by 8 Vpp for most of the last day. Oops. The attached image shows what effect
this had in the MC transmitted power (not negligible). This would also make the locking pretty difficult.
In the second plot you can see the zoom in view for ~30 minutes. During the first part, the MCWFS are on and there are large fluctuations
in the transmitted power as the WFS offset changes. This implies that the large TEM00 carrier offset we induce with the slider couples into
the WFS signals because of imbalances in the quadrant gains - we need someone to balance the RF gains in the WFS quadrants by injecting
an AM laser signal and adjusting the digital gains.
Since there is still a modulation of the MC RFPD DC with the WFS on, we can use this to optimize the REFL OFFSET slider. The third plot
shows a 8 minute second trend of this. Looks like the slider offset of zero would be pretty good.
This morning, MC alignment was gone and MC wasn't lock.
We checked old value of pitch, yaw, and position offset of each MC mirror, and found they were jumped.
We don't know the reason of this jump, but we restore each offset value and MC backed to lock.
Kakeru and Kiwamu
We placed a QPD on the PSL bench for PSL angle monitor.
I checked a broken QPD, which was placed for PSL angle monitor, and finally I cocluded one segment of the quadrant diode was broken.
The broken segment has a offset voltage of -0.7V after 1st I-V amplifier. It means the diode segment has a current offset without any injection of light.
Tomorrow I will check a new QPD for replacement.
As we mentioned before, old QPD which used to be placed is broken.
And we put broken QPD into the "photodiodes" box under the soldering table.
We found the MC reflection was distorted . And WFC beam went to upward of QPD
We recentered WFC beam and these problems were fixed