J. Kissel, Cheryl, Sheila, Jenne, Betsy, Jim, Keita, Rahul
Since morning I have been working on the health checks for the QUADs (ETMs & ITMs) and Beam splitter, after we were stuck by 6.5 scale Boise earthquake, as reported by Corey (alog 55838). Jeff. K (and Betsy/Sheila) suggested an extensive health checklist and I am in the process of ticking them off one after other. Given below are the results from today’s measurements. These measurements were performed after coordinating/discussing with many folks remotely (due to COVID-19 Phase 3 state for LHO).
- I glanced over suspensions overview screen and checked for damping loops for the main chain as well as reaction chain. Nothing abnormal, the M0 damping loops were working normally for the main and reaction chain for all the ETMs/ITMs and BS.
- CENTERING (checking the speed dials): I checked if the speed dials were within their normal range (counts: 10k – 20k approximately). I also checked if the values were fluctuating or was constant (like dead).
ETMY, L2 stage inmon values were found to be at 5k, which dropped from 10k after the earthquake. Please find attached an ndscope plot which shows the same. The speed dials for other optics looked fine.
- OPLEV/OPTICALIGN measurements: I took a work permit (no. 8586) to perform the OPLEV measurements to check if the the bottom stage optics moves with the sldiers. Given below are the pitch and yaw numbers which I found,
|
Optics |
Pitch values urad (HEPI OFF) |
Yaw values urad (HEPI OFF) |
Comments based on moving the sliders |
|
ETMX |
37.2 |
-6.3 |
movement observed as expected |
|
ETMY |
-50.4 |
3.9 |
movement observed as expected |
|
ITMX |
-27.3 |
-3.9 |
Very tiny (negligible ) movement observed for the pitch. Yaw looked fine |
|
ITMY |
-5.9 |
19.3 |
movement observed as expected |
|
BEAMSPLITTER |
15.0 |
11.8 |
movement observed as expected |
On moving the OPTICAIGN sliders, I found that ITMX pitch did not change much (0.2 urad change in pitch values, while moving the sliders by 20 urad). Also, for the ETMX and ETMY the pitch values are higher than the typical values (+- 17 urad is highest I have seen).
The above Measurements were done while the HEPI was OFF. Hence, Jim turned the HEPI ON for ETMY and ITMX only. During this time the the Pitch and Yaw for ETMY was recorded as -52.9 and -2.9 respectively. Also, for the ITMX the pitch and Yaw numbers were -27.3 and 2.6. Hence, no significant change was observed after the HEPI was turned on. ITMX pitch was still stuck at -27.3 urad (+- 0.5 urads) on moving the OPTICALIGN sliders.
Next I will be performing a hysteresis measurements on ETM/ITMs and will alog the results. There are many more health checks still left to be performed, I will keep on posting the results as I have them.
I have added ndscope plots for ETMX, ETMY and ITMX, showing the OPLEV pitch values which changed after the earthquake.
Adding an SEI tag to this post. This earthquake event might suggest watchdog updates. Certainly time for a followup with the Washington & Oregon ShakeAlert folks. We've asked to be added to their beta-test notification system, but it has not happened yet. Like the previous ~local quake, this event came from an area not yet covered by that system, but it's still a firm prompt.
The ITMX is no longer on the OPLEV after the Tuesday EQ, so looking at OPLEV channels for this SUS is not valid.