Takano

This work was done yesterday.

I checked the sensitivity with changing the amplitude of the dithering at 5000.1 Hz for sening OMC length signal. I changed the gain of K1:OMC-PZT_LV from 0.1 to 2. To keep the open loop transfer function unchanged, I also changed the gain of the feed back filter.

Figure1 shows the results; I plotted the power spectra of OMC TRANS (normalized) and the error signal of OMC length control. When the dither filter gain is less than 0.2, an excess noise appears between 20 and 250 Hz. When increasing the gain, no significant change could not be seen. But unfortunately when I took the data with higer gain the floor noise level got worse, and so it could happen that the effect of increasing the amplitude was just buried beneath the floor noise.