So far it was pointed out that when a large offset on the End IPs stage along L direction is applied to compensate the tidal effect, because of L2Y coupling a large drift in TM_Y is observed.

Today I tried to estimate and reduce this coupling.

%%% ETMY%%%

I changed the offset of the IP from 0 to 100 microns and I looked at the variation of the TM_L and TM_Y and I estimated that L2Y coupling was about 14 %.

I changed the L2Y coffecient in the sensing matrix from -0.5247 to -0.5166 and I measured again the coupling (about 1%) (see Pic1)

%%% ETMX%%%%

I changed the offset of the IP from 0 to 100 microns and I looked at the variation of the TM_L and TM_Y and I estimated that L2Y coupling was about 4 %.


I changed the L2Y coffecient in the sensing matric from -0.2262 to -0.662 and I measured again the coupling (about 1%) (see Pic2)

I hope that these values are small enough to keep the IFO aligned.