NAOJ GW Elog Logbook 3.2
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YuhangZhao - 00:34, Wednesday 10 July 2019 (1454)
Replacement of Green phase shifter base plate(thick post for mirror mount)
Pierre and Yuhang
Since Matteo designed the new base plate for the new mirror mount (RadiantDyes), I replaced the old base plate with this new one. This new one has two holes in the plate, so we expect it to have a better performance.
After the replacement, I tried to lock again with the new MZ/GRMC servo realized by Pierre. But at that moment, we didn't succeed. The reason was found out that somehow GRMC transmission was reduced. Now the highest power we can have for GRMC transmission is around 55mW.
Then we tried to find the coherent control error signal for CC1. But we failed. We will try to figure out the reason tomorrow.
After I did this replacement, I found there is a new peak appeared. Compared with the alignment Chien-ming did for GRMC, this additional peak has a much higher height.
Today I use a camera to check this peak and it shows shape like the attached figures.
But I think this is not a big issue since we just need to lock on TEM00. But we will lose some power.
Aritomi and Yuhang
I found beam was cut obviously at the output port of MZ. The cut position is shown in the attached figure 1.
There is also a very good point to check if the beam is cut or not. In the attached figure 2, the shown place is a round shape. But when the beam was cut, I saw clearly there is an unfilled corner.(I am sorry I didn't realize to take a picture at that time)
In the attached figure 3(cut) and 4(no cut), you can see the difference before and after solving the problem of cutting. The higher order mode becomes a lit bit lower. After that we tried to change the offset of MZ servo, then we found we could reach GRMC transmitted power of 70mW. This meets the requirement of high BAB amplification for filter cavity alignment.