[PatrickT, Jenne]
We've struggled to keep Yarm ALS locked this morning since we have particularly bad ground motion today. We started down a path of trying to figure out why.
The Yarm SUSPOINT length projection from the seismic tables doesn't seem very coherent with the power fluctuations in the Yarm. This led us to look at the angular motion of the optics.
In the attached ndscope figure, you can see that the oplevs for ITMY and ETMY, pitch and yaw are on the same y-axis range of 0.8 urad. However, ITMY pit is moving more than this scale. (Stefan has some plots up that show that a similar phenomenon is happening on the Xarm).
We took a measurement of the ITMY pit oplev loop, with a thought toward using the oplev to damp this motion. However, before we go further down this path, we're looking with Sheila and Stefan if there are any inconsistencies in the seismic isolation or suspension top stage damping that may have potentially come in during some maintenance or computer reboot time.
I've added links to BRS overviews for the non-existent CS BRS to the ISI-CONFIG screen so we have an easy way to check the status of these paths in the future. They're in the bottom left quarter of the screen, above the configuration guide. I had to modify the ITMX/Y bsc-isi macros to get them to work, which breaks Hugh's clever "Not Built" labels on the ISI overviews.
*This comment is a follow up to the comments below. Why is this post appearing above the earlier comments? It makes no sense out of order...*
J. Kissel, H. Radkins, J. Warner Problems appear to arise from a factor 2.0 error in the sensor correction system to the ITM ISIs. Actively under investigation. Band-aid solution for now is to turn down the calibration of the ITMY STS for the entire corner by 0.5 via the STS selection matrix elements in H1:ISI-GND_STS_MTRX channels. It looks to be a problem with the newly installed super sensor generation in the corner (ISI_GND_SENSCOR_ITMX or ISI_GND_SENSCOR_ITMY) which only affects the X and Y DOFs. As we know and have begun to hate, all new filters get started in the front end as input ON, output ON, and a gain of 1. THIS SUCKS. Since LHO has no corner station BRSs, we want any correction paths to be OFF. However, the TORQUE correction path for the STS was ON as a direct pass through, and thus doubling the signal. As soon as I post this aLOG, Hugh and I will rip off the bandaid solution, and make the real fix. Unrelated confusing, but inconsequential error: STS mapping of the three corner station STSs on the way to the new seiproc model might be screwed up. See attached images. According to D0901301, the third card, ADC3, in the h1 isiitmy I/O chassis receives the STSs in the following order: Location Physical Nickname Electronics Name ADC Channels for BSC1 aka ITMY (the blue text in the drawing) HAM2 HAM2 STS A X 23 Y 24 Z 25 Beer Garden ITMY STS B X 26 Y 27 Z 28 HAM5 HAM5 STS C X 29 Y 30 Z 31 And this is the order in which the ADC selector attached to the ADC3 part in the h1isiitmy model is broadcasting the signals. However, the *bus creator* that receives and concatenates these signals into a tag *incorrectly* labels things in a different, labeling 23-25 (STSA/HAM2) to "26-28 (STSB/ITMY)", 26-28 (STSB/ITMY) to "23-25 (STSA/HAM2)", and leaves 29-31 (STSC/HAM5) correct. Thankfully, at the other end of the tag, the bus selector -- retaining this incorrect order -- maps the signals to IPC connections that are in the end, still correct, such that STSA/HAM2 gets broadcast as STSA, and STSB/ITMY gets broadcast as STSB. We should fix this, but *phew*.
First image is the offending doubling in the "BRS" area. The STS_X_TORQUE filter path was ON as JK says but with no filters so passing through and doubling the SUPER_X(Y)_OUT.
After correcting this by ramping the TORQUE gain to zero and the selection matrix gain (e.g. H1:ISI-GND_STS_MTRX_1_4) back to 1, the signals look back to correct--see second attachment:
The solid references are from hours ago and the 2x is evident comparing the ground STS to the SENSCOR SUPER OUT. The current dashed traces have those signal now just overlapping (reduced BW-sorry) and the same as the earlier GND signal.
Will attach attack SDF now for posterity. SDF values updated.
