[Michimura, Enomoto, Nakano, and more]

We succeeded to control the MICH with RF demodulation signal.

Procedure

1.Gained the error signal

When the IFO got re-aligned as this entry, the RF staff for MICH control at dark fringe were ready as this entry. Those worked without any problem and we got the error signal from a I&Q demodulator.

2. Adjusted the I&Q rotator angle

I rotated the I&Q rotator angle in the MEDM screen so that the I signal get smallest. (You should be careful that the measured difference in the MEDM screen of the I&Q rotator should be set to 90, the default of this number is zero.) The amplitude of the Q signal, which is the error signal, was 9000 counts peak-to-peak

3. Changed the sensing matrix

The sensing matrix for MICH was changed, I swap the signal from DCPD to from RFPD-Q to fed back. 

4. Optimized the gain

A gain of a MICH servo was set to -50. It was decided to make UGF to 100Hz. 

5. Modified the guardian

The MICH guardian modified for the RF locking, and checked that worked well.

Next

The MICH will be operated over night with this configuration. We will see how stable it is.

We would aligned finely with locked MICH at dark fringe. The visibility is around 60 % and can get better. 

The noise budget would be done by some students.