I found that it apeared the offset in WFSf3. I manually moved ITMX to center the ETMX beam position. Now, FIG1 and FIG2 are when I put an offset in PIT and when you put an offset in YAW. The transmitted power has increased slightly. I need to find out what causes this. I also want to consider how far I can investigate the schedule. I will write more details later.
I tried the same experiment again today. PIT and YAW are FIG1 and FIG2. They are offsets. Changes due to offset cannot be detected in the PRCL OUTPUT signal. I don't know if this offset is uniquely determined, but it is hard to think that it is an offset due to length.
In FIG3, I added an offset to the PRCL signal, and the POPRF90 power is highest when the offset is 0. It appears to be WFSf3 due to the change in the L2A signal or REFL power.
I also thought that by installing ITMX's BPC, I could reduce the number of candidates for offset factors by suppressing drift. However, if you want to detect the ITMX signal from REFLRF45, it will be difficult without changing the current k1LSC and k1BPC models.(FIG4: k1LSC,FIG5: k1BPC)
Also, when moving with the IMMT2 PIT, the movement of the IMMT2 PIT appears in the WFS signal. Setting the offset of WFSf3 increases POP90. There is also a possibility of IMMT2 coupling. (FIG6)
This time, the possibility of an offset due to the DC centering loop is also suggested.
In addition klog30739 work to the RF90 centering loop installation, I need to set the model to normalize with SUM like DC(FIG7).
I also examined the coupling of the WFS signal with IMMT2. (/users/Commissioning/data/ASC/2024/PRXARM/20240820/Coupling_IMMT2_{PIT/YAW}_20240820.xml)
| ERROR/OPLEV | |
| PIT | 7.97 |
| YAW | 15.56 |
This is an additional explanation.
Originally, WFS used a DCcentring loop to eliminate the offset of the length signal. However, in the case of WFSf3, because it detects beat signals of RF45 and RF56, a centering loop using an RF signal at twice the RF45 should have been designed. However, the conventional DCcentring loop is now set by klog30793. Therefore, there is a concern that the offset of the length signal is not canceled.
However, as shown in FIG3, when an offset is set to the PRCL signal, the POPRF90 signal is at its maximum when it is 0, so the length signal is not detuned and is controlled by the LSC. The offset due to the length may be shown by DCcenteringloop, but according to FIG3, the offset may not be visible and may be small enough. I would like to prepare a model with an RF90 centering loop, for that it may appear in PRFPMI.
It is certain that a mysterious offset has appeared in WFSf3 in FIGS. 1 and 2, but I don'tm know what it is coming from. I haven't done a test yet where I set an offset on the CARM and detune it, but it's indistinguishable from RFAM. It could be a coupling issue. BPC control of IMMT2 is possible from PRCL, so it may be worth trying.
Also, regarding the offset setting of WFSf3, the current DCcentringloop range is narrow and it is not possible to set a large offset, so I do not know which is the optimal offset.