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MIF (General)

hirose.chiaki - 5:56 Wednesday 01 February 2023 (23596)

Yarm trans power was 20% lower.

Hirose, Tanaka(remort)

Before starting Yarm ASC work, I let Yarm lock. However, on the 29th and 31st, Yarm trans power was lowered by 20%.
We do not know the cause.

When ADS (TMSY->IMMT 2, PR2) was turned on, it maximized to 0.8, not 1.
Checked their channels. (Trans of IMC, SUM of QPD1 in IMMT2, SUM of QPD1,2 in POP FOR, OUTPUT of PD in REFL and POP)
-> When TMSY power was lower, the incident power was not changed much and reflected power was changed lower. (I don't understand the reason.)
Checked the channels of the beam spot of TMSY QPD.
->QPD2 was changed a little.

How to read the figures
I worked on it for about 4 hours every last 3 days.
In the figure, Yarm was locked for about 4 hours from "2day6h", "1day6h" and "6h".
Before "2day6h" and "6h", Yarm trans power was 0.8.
Before "1day6h", Yarm trans power was 1.0.

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Comments to this report:

takafumi.ushiba - 16:10 Wednesday 01 February 2023 (23788)

Hirose-san,

I checked the relations of Y arm transmission power and REFL power.
Figure 1 shows the time series data of TRY NORM and REFL PD output.
Left T cursor shows the timing when TRY NORM is about 1 while right T cursor shows the timing when TRY NORM is about 0.8.
As you can see, REFL power at left T cursor is about 0.23 while right is 0.017.

Since the single arm lock is managed so as locking stably only when REFL power is around 0.23, it might cause problems.
So, please check IFO REFL power if you feel Y arm lock is strange.

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