This is a summary of the PR trips occurred recently.

SInce the beginning of O4, almost 3 days, we had 15 trips. At least ten of them would have unlocked, but the feed-forward prevented it. Only one unlocked the ITF: it was the smallest one, almost invisible in PR_F0_TY, but anticipated by the usual fast glitch on the accelerometers as all the others. Its impact would have been null, but the anti-trip applied by feed-forward produced 6 V of locking correction, enough to unlock.

Considering that the correction resulting from the largest trip was 5 V, it has been decided to reduce e little bit the amplitude of the back action. After this modification, the largest trip arrived at 5.5 V of correction and the ITF survived.

It is clear that we are at the limit and there is the possibility of an unlock both with the large and the small trips. So far we have been lucky and we can hope that things will continue like that, but it would be better to have something a bit more robust. The variable back action, based on a measurement of the foreseen amplitude of the trip, seem a feasible strategy, but needs to be validated on the machine.