[Miyoki, Nakano]

Since we tweaked the loop gain of ALS PDH, PLL, and FNC without careful investigation, they often got unstable these days. We went into the mine and check those loops. Also the ALS CARM has been modified. As the result, the ALS DARM signal has been improved by blue to red in the first attached figure.

• I summarized the OLG of each loop in https://gwdoc.icrr.u-tokyo.ac.jp/cgi-bin/private/DocDB/ShowDocument?docid=12016
• I made several templates to check the ALS performance. these are located in /kagra/Dropbox/Measurements/IFO/ALS
• PLL/PLL_ERR_FB.xml is the template to check the PLL performance. It shows the error signal and the feedback signal. I took the reference when the PLL is locked, and any other loop is not.
• PDH/PDH/ALS_PDH_ERR_FB.xml is for the ALS PDH loop. The reference of each signal was when the PDH and the FNC loop has been closed. No ALS_CARM, ALS_DARM, and so on. Ref4,5 is the feedback signal without FNC.
• FNC/FNC_ERR_FB.xml shows the error signal and feedback signals of the FNC loop. The reference is the ones when FNC and PDH loop is locked.
• ALS CARM loop OLG is shown in the attached figure. UGF is 2 kHz with 40degrees of phase margin.