All in-lock charge measurements taken this morning using the SUS_CHARGE guardian after taking ISC_LOCK to NLN_CAL_MEAS. Analysis following wiki. Plots attached showing data from this year only.
We had a lockloss while transitioning ESD control back from ITMX to ETMX: 1362334890, lost lock 8 seconds into the 20second ramp between ITMX and ETMX L3_DRIVEALIGN_L2L. See attached plot. I'm not yet sure the the exact cause. The SUS outputs don't look too bad but the ASD monitors show a large excursion in the 8 seconds before lockloss, see plot.
To improve these charge measurements:
- Some of our ramp times might be longer than needed
- These is a few SUS output spikes that we should look into the cause of
- Do we need to be in NLN_CAL_MEAS, this will be tricky once the measurements are automatic. What NLN_CAL_MEAS steps do we need to take?.
- Sheila suggested also including the effective voltages in the anaylis (equations 7 and 9 from T1700446).
| Previous Measurments | ITMX | ITMY | ETMX | ETMY |
| 2023 March 08 | yes | yes | yes | yes |
| 2023 March 01 | X | X | X | yes |
| 2023 Feb 10 | yes | yes | X | X |
| 2022 July 29 | X | yes | yes | yes |
| 2022 July 14 | yes | yes | X | yes |
| 2021 May 14 | yes | yes | yes | yes |
The lockloss was caused by the SUS_CHARGE guardian setting the ETMX_L3_DRIVEALIGN_L2L gain back to an obsolete value which corresponded to a different ESD bias. The gain was hard coded to the old -35.7 value, see attached plots, but recently the drivealign gain was updated for the new low-EMI-coupling ESD bias (alog 67698 and alog 67831).
I edited SUS_CHARGE.py:
- Adding a line importing lscparams
- Setting the drivealign gain to the
lscparams.ETMX_GND_MIN_DriveAlign_gainif we change for example the name of the parameter in the future we'll need to update the SUS_CHARGE guardian too
