Fujimoto, Hirose, Tanaka
## SRM ADS
SRM ADS also improved AS34. It seems to be reproducible yesterday's setting (fig.1). We implemented it to the ASC_LOCK guardian
## BS ADS trial
### change dither frquency
#### from 22.125 Hz (PIT) and 24.125 Hz (YAW) to 36.125 Hz (PIT) and 38.125 Hz (YAW)
BS oplev seems to have a peak at 24 Hz even though we don't inject any excitaion to BS (fig.2). So we decided to change the dither frequencies. We looked into the frquency region. There are no peaks both in POP90 and in AS34 above 35 Hz. We changed the dither frequencies from 22.125 Hz (PIT) and 24.125 Hz (YAW) to 36.125 Hz (PIT) and 38.125 Hz (YAW). We used the ADS-{PIT,YAW}_{TMSX, TMSY}_DEMOD_SIG_OUT channels as AS34 and ASDC signals. We measured the demod. phases by POP90 (fig.3), AS34(fig.4), and ASDC(fig.5) several times. And we remeasure the deomod. phases every lock restorements. As for ASDC, AS34, there seem to be low coherence about BS alignments even though peaks are observed in ASDC or AS34. On the other hands, in POP90, there are some coherences. However, YAW phasing seems to be no reproducibility. Therefore, there seems to be other coupling, for example, L to Y.
Unfortunately, Since MICH Lenght control UGF is close to these dither frequencies, we could not engage resG filters. We considered that L2Y coupling can be decreased by changing the rotation center of BS but this adjustment depends on the beam position on BS and the position is changed by the alignements of DRMI. Therefore, we changed the dither frequencies again to lower frequencies and tried to decrease the L2Y coupling by implementing resG filters in MICH loop.
### from 36.125 Hz (PIT) and 38.125 Hz (YAW) to 16.125 Hz (PIT) and 14.125 Hz (YAW)
We looked into the frequency region again. Then, around 14 Hz, 16 Hz, and 18 Hz, there seems to be no peaks. So we tried to implement YAW and PIT ADSs with 14.125 Hz and 16.125 Hz, respectively. We confirmed the reprocibility of phasing if we use the resG filters in MICH filters. I tried to engage the BS ADS but PO90 decreased (fig.6). Also, SRM seems to move the opposite direction when BS ADS was engaged
