Camilla, Rahul
SUS ZM2 in HAM7 chamber needed a pitch offload since it was using up a lot of DAC output. This morning we went to HAM7 chamber and at first confirmed the beam alignment and its position on the irises. Then I entered in HAM7 chamber and locked the suspension and unlocked the pitch adjuster screw. At first I gave it a full 1 turn anti-clockwise making ZM2 pitch down (and then unlocked the suspension) and Camilla confirmed that the alignment looked better but perhaps we overshot by a small amount. I retracted by 1/4 turn (thus making 3/4 turn anti-clockwise in total) and then the beam looked good on the iris. Before exiting the chamber I locked the screw for pitch adjuster and checked if all EQ stops were set free from the suspension chain.
Finally Camilla adjusted the alignment sliders on ZM2 for fine tuning it.
I took a quick chamber side transfer function measurements and the suspension was found to be healthy.
While I was fine tuning the alignment after this offload, I realized that the PSAMs setting was wrong. It appears that while this ZM2 work was happening that the ZM2 strain gauge reading has been shifted. We still have the same ΔV of 5V but the range used to be 1.2 to 6.2V plot and now is 4.6 to 9.6V plot. CIT has possibly seen this before in T2300426 but the effect was less.
Our nominal was 3.15V before, now I'm assume it should now be 6.55V (4.6V + (3.15V - 1.2V)). We will confirm this with beam scan measurements in chamber.
Ryan and I went to ZM2 PSAMS strain gauge at 6.55V and took data in 2 similar locations to in 91142. The beam size lis very similar to expected so we think ZM2 is fine, just the strain gauge now has an offset. Will look at the data in more detail tomorrow.