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H1 ISC
elenna.capote@LIGO.ORG - posted 13:03, Thursday 29 August 2024 - last comment - 09:23, Friday 30 August 2024(79799)
New HAM1 FF for CHARD P and INP1 P - Improvement

We did a 10 minute on/off HAM1 FF test today. I determined from that test that improvement could be made to the feedforward to CHARD P and INP1 P, so I used that off time to train new filters (time here: 79792).

I took a screenshot of the DTT results. The golden traces represent the various loop spectra with the feedforward OFF. Blue represents the previous feedforward, and red represents the new feedforward I fit today. First, look at the top and bottom plots on the left, showing CHARD P and INP1 P. You can see that the old feedforward was having minimal benefit (gold to blue), and the new feedforward is performing much better (gold to red).

Next, look at the middle plot on the left showing CHARD Y. This plot shows that the feedforward is making CHARD Y WORSE (blue worse than gold). Therefore, I just turned it off. I am not yet happy with the fitting results for CHARD Y, so I will continue to work on them.

You can also see in the middle right plot, PRC2 P current feedforward is performing well (gold to blue), so I made no change, red still matches blue.

Note! This means the significant change here must be related to RF45- PRC2 is only sensed on RF9, while INP1 and CHARD use RF45.

Finally, DARM on the right hand side shows improvement from blue to red. It looks like HAM1 FF off is better below 15 Hz, maybe due to CHARD Y.

The new CHARD P and INP1 P filters are all saved in FM9 of their respective banks. I SDFed the new filters, and the CHARD Y gains to zero, second screenshot.

I made one mistake which is that I did not SDF these changes in SAFE, only in OBSERVE, which means that needs to be done before an SDF revert, since they are not guardian controlled!

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elenna.capote@LIGO.ORG - 09:23, Friday 30 August 2024 (79816)
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