I continued the trial of high bandwidth ASC.

## Frequency dependent MN actuator balance

First of all, I tried to take a balance of Type-A MN balance. In the original low-band width ASCs case, we used TM and MN stage as the actuator. A cross over frequency between their stage was 0.1Hz. At that time, we took the actuator balance by using TM and each MN actuator effeiceincy was tuned respectively so that the cross-over frequency became 0.1 Hz (klog). On the other hand, in the high-band width ASC case, we will use only MN stage as the actuator, So, I confimed the the MN actuator efficiecy by measuring the frequency responce of TM oplev when MN was excited.

This TF measurement setup is as below

• Type A suspension guardian state: Lock acquisition
• Turn off both P and Y TM oplev DC controls by engaging null filters in FM9 of {I, E} TM{X, Y}_MN_OLDAMP_{P, Y}
• Excitation signal was injected from DHARD_P_SM_EXC. This time, OUTMTRX was not changed.
• Only gain filters in MN_LOCK filters were engaged, that is, I turned off FM4, FM9 and FM10 in this time.
• TM_LOCK gains were set 0 so that the excitation did not feed back to TM stages.

Fig.1 shows the results of each frequency responce of each TM oplev when each MN was excited. Each DC gain seems to be almost the same, but each gain above 1 Hz seems to be different due to the resonance frequecy's difference (especially ITMY).  Since MN stages were used as the actuator below 0.1 Hz previously, it maybe ok that the just each DC gain was aligned. However, this time, we want to enhance the bandwidth up to several Hz. it may be necessary to adjusted the gain in both DC region and several Hz region. So I attempted a frequency dependent MN actuator balance by implementing frequency dependent gain filter in each MN_LOCK filterbank. This time, I adjusted other 3 Type As' responces based on the ETMX responce,

I summrized the each gain value at 0.14 Hz as a representative DC gain and at 3 Hz as a representative higher freq. region and the difference from ETMX.

As for ITMX, I just adjusted the overall gain by implementing -3.45 (=(3.6+3.3)/2) dB in FM2 of MN_LOCK. As for ITMY and ETMY, I made the filters like fig.2 so that the both gains at 0.1 Hz and 3 Hz were almost the same as the ETMX. In this time, I did not take into account the gain around the 0.8 - 1 Hz. Such filters were labeled "test", and implemented in FM2 of ETMY_MN_LOCK and in FM6 of ITMY_MN_LOCK respectively.

After the implementation, I measured the responces again. Fig. 3 shows the results. the frequency dependent balance seems to work well.

## DHARD and CHARD P

I engaged DHARD P control with new filter. Also, I used the same filter as DHARD for CHARD P control. Fig. 4 and 5 show the OLTFs of DHARD and CHARD, respectively. Their UGFs are set to 1.5 Hz.

Fig.6 shows the spectra of ASC error signals. As for DHARD P, RMS after balancing seems to become bigger than the one before balancing, but it is still lower than the one of old filter.

## Note

I found that there is still couplings. fig. 7 shows the timeseris of the error -feed back of ASC during CHARD _P OLTF measurement. Although CHARD_P was excited, DHARD_P error signals.