KAGRA Logbook

MIF (ITF Control)

masayuki.nakano - 3:39 Monday 03 February 2020 (12747)

Weekend IFO work

MICH 1f

- The MICH1f loop is not really stable. It lost lock every a couple of minutes.

- I tried to adjust the offset, demod phase, and so on, but they are not helpful.

DC-readout

- I tried to hand-off to the OMC DC signal. I measured the relative gain, and the attached file shows that.

- I put 3e-4 as the DARM offset and then mixed the OMC DC signal into DARM servo. I tried to hold the DC output at 50 cnts, but it was kicked within 30 sec. The attached time series shows when I tried. Maybe the offset is too small.

Images attached to this report

Comments to this report:

masayuki.nakano - 4:00 Monday 03 February 2020 (12748)

I put several inv-filters into K1:LSC-OMC_DC filter bank. Now the relative gain is unity.

Also I found that the current zero point of RF error signal is not really zero, and the AS has some DC light. It seems good point for DC-readout as shown in attahced figure.

Images attached to this comment

yoichi.aso - 15:55 Monday 03 February 2020 (12758)

In LIGO, they seem to use 20mW as the DC readout operation point.

This corresponds to 11800 cnts in K1:OMC-TRANS_DC_SUM.

So 50 cnts was probably too small.