IM2's alignment changes after a shaking event (ISI trip) such that the alignment drive is unchanged, but the pointing of the optics (as measured on OSEMs) is different.

These jumps in alignment are anywhere from 5urad to 42urad in pitch.

IM2 is the most effected, but IM1 and IM3 also show this behavior.

I've looked at six shaking / alignment change events, and recorded the amount of motion (shaking) the optic, ISI, and HEPI experienced.

The results shows that the amount of HEPI-ISI shaking can vary during an event that results in a change in IM2 alignment.

What is consistant is the average amount the optic shakes (pitch plus yaw divided by two) to produce a jump in alignment are between 2.1 and 6.1 urad of optic alignment change per urad of average optic shaking.

This suggests the conclusion that optic shaking is the cause of the alignment change, however, in looking at a few events where the optic tripped but HEPI and ISI didn't, I have not seen a significant alignment change, so this part of the IM alignment jump investigation is ongoing.

Based on my curent data, the mechanism that creats and alignment jump on IM2 is a combination of optic shaking and HEPI-ISI shaking.