Reports until 14:05, Wednesday 26 June 2019
H1 ISC
jenne.driggers@LIGO.ORG - posted 14:05, Wednesday 26 June 2019 - last comment - 14:59, Tuesday 02 July 2019(50209)
Identifying the 10.43 kHz mode

[Georgia, Jenne]

Comments related to this report
georgia.mansell@LIGO.ORG - 15:00, Wednesday 26 June 2019 (50213)

Terra called the control room and helped me excite the mode by increasing the gain in the dampining filter for mode 24 (no excitation required). We excited the mode until the PI_ESD_DRIVER_OUT monitors were several thousand counts. Though as we increased the gain we saw some broadband noise around our mechanical modes.

We set the ESD output matrix in the butterfly configuration (diagonal quadrants out of phase) and managed to ring up the slightly-lower-frequency 10.428 kHz mode (see first attachment, red is with the mode rung up). We then switched to the drumhead configuration (diagonal quadrants in phase), and managed to ring up the same mode again. So as yet we have not distingushed which mode this really is.

They saw something similar at LLO, and looked at the downconverted transmon QPD signal to distinguish between the two modes. During the first round of excitations I had the TR_Y QPD input matrix in the drumhead configuration (all quadrants added together). For the second round of excitations we switched the matrix to a pringle-mode. I will need to look back at the data and see if we saw our down-converted excited mode in the QPD.

 

Second attachment is the broadband noise with the ETMY ESD bias on, as noted by Jenne above.

Images attached to this comment
peter.fritschel@LIGO.ORG - 11:35, Thursday 27 June 2019 (50247)

The beams on the TransMon QPDs are so off-center that it might be hard or not possible to identify the modes using them. On each QPD (A & B) the lowest light segment has about 20x less light on it than the highest light segment. I think you'll need to center the beams on the QPDs to use them as a diagnostic.

georgia.mansell@LIGO.ORG - 17:24, Thursday 27 June 2019 (50251)

I had a look anyway, and only see the downconverted mode when the Transmon QPD input matrix is in the pringle configuration, suggesting that the 10.427 kHz mode is a flower mode of ETMY. (I'm not sure if this is using only one QPD or some combination of both, it's not obvious to me from the PI screen.)

We didn't manage to ring up the 10.4305 kHz mode with our ETMY excitations, perhaps it is on a different test mass?

Images attached to this comment
georgia.mansell@LIGO.ORG - 14:59, Tuesday 02 July 2019 (50354)

The last plots in this thread could be misleading. Slawek has pointed out that the QPDs should see the second order optical mode, but the linewidth we saw was too narrow for this... Maybe some electronic cross-talk?