Reports until 04:50, Tuesday 04 June 2013
H1 IOO
kiwamu.izumi@LIGO.ORG - posted 04:50, Tuesday 04 June 2013 - last comment - 10:41, Tuesday 04 June 2013(6610)
IMC WFS commissioning : not sensitive to MC1/MC3

I am in the process of measuring the sensing matrix for the IMC WFS.

An issue I have been facing is that both WFS-A and B seem quite insensitive to the angular motion of MC1 and MC3. no

 

(measurement of sensing matrix)

To measure the sensing matrix the way I have been doing is that :

  1. Excitation on one of the MC mirrors in either YAW or PIT. I usually excite the very bottom stage at around 5 Hz with amplitude of 200 - 10000 counts in LOCK_P/Y_EXC.
  2. Monitoring of the excitation lines in diaggui in both WFS-A and B to make sure that the excitation is big enough.
  3. Take a transfer function (or transfer point at the excitation frequency) from the excitation point to the WFS sensors.

I always get a signal with a high SNR when MC2 is excited. This is good. However the signal is always quite small when MC1 and/or MC3 are excited. In fact WFS-A and B are unable to detect the excited motions. I am not sure why at the moment. My feeling is that they behave as if the actuators on MC1 and MC3 are super weak.

Comments related to this report
suresh.doravari@LIGO.ORG - 10:41, Tuesday 04 June 2013 (6613)
Link 

In L1 we used the 'Witness' channels (such as L1:SUS-MC1_M3_WIT_PMON) to look at the actual motion excited in M3 while the drive was applied to M1.