The goal of this shift was to continue the work started yesterday afternoon, i.e. to compensate the north CP cold lens with the DAS power.
Since last time we checked several values of the outer ring, this time we decided to start from the best point of yesterday (Inner ~70mW, outer ~1W) and to change only the inner power.
To be noted that, as explained after the morning shift, in order to avoid misalignment of PR/BS and arms we perform an unlock/realignment each ~20-30 minutes and we use the new function for the drift control of the arms on the green during all the scans.
A summary of all the several steps performed are shown in figure 1. It seems that the last power chosen for the inner ring (~700mW) improved a lot the north arm matching, which is now close to the west one. Also, it appears that after ~45 minutes we reached the minimum for the north matching . It is maybe worth to fine tune tomorrow morning the inner power around the last chosen value.
In agreement with Alessio, we then decided to leave the arms locked in IR with the North Inner DAS ON.
Below a detailed list of the actions:
We first scan the TEM0 and TEM2 with only the inner NI ring switched on at 14:06 UTC for TEM00 and 14:16 UTC for TEM02
We then put the outer DAS at 1W:
1337005078 19 May 2022 14:17:40 UTC (19 May 2022 16:17:40 CEST)
and we leave the scan of TEM2 going on.
Unlock & cavity realignment
1337006416 19 May 2022 14:39:58 UTC # self unlock
1337009119 19 May 2022 15:25:01 UTC (19 May 2022 17:25:01 CEST)
Scan of the TEM0 mode
1337009456 19 May 2022 15:30:38 UTC (19 May 2022 17:30:38 CEST)
Unlock & cavity realignment
1337010062 19 May 2022 15:40:44 UTC (19 May 2022 17:40:44 CEST)# self unlock
After thermalized, we do a first step on the inner ring, doubling its value from 60 to 120mW:
1337010492 19 May 2022 15:47:54 UTC (19 May 2022 17:47:54 CEST)
and then we start back the scan on TEM02
Unlock & cavity realignment
1337012028 19 May 2022 16:13:30 UTC (19 May 2022 18:13:30 CEST)
We do a TEM00 scan
1337013927 19 May 2022 16:45:09 UTC (19 May 2022 18:45:09 CEST)
The matching seems to improve, thus we decide to double again the inner das up to 250mW:
1337014819 19 May 2022 17:00:01 UTC (19 May 2022 19:00:01 CEST)
Unlock & cavity realignment
19 May 2022 17:08:30 UTC
1337015565 19 May 2022 17:12:27 UTC (19 May 2022 19:12:27 CEST)# self unlock
At this time, we experienced a failure while doing the Fmoderr with the automation and we found out that it was due to the hardware. In fact the LNFS (low noise frequency synthesizer, for the 56, 6 and 8 MHz sidebands generation) was in a faulty state. We solved it by switching off and on again but the data acquired till 17:30 UTC are not reliable.
Once the LNFS problem solved, we start again with a TEM00 scan
1337018984 19 May 2022 18:09:26 UTC (19 May 2022 20:09:26 CEST)
We start back to scan the TEM02
19 May 2022 18:17:35 UTC
Unlock & cavity realignment
1337020729 19 May 2022 18:38:31 UTC (19 May 2022 20:38:31 CEST)
We unlock again to start the new measurement, and we do a TEM00 scan
1337021485 19 May 2022 18:51:07 UTC (19 May 2022 20:51:07 CEST)
The matching seems to improve, we decide to double again the inner das up to 410mW
1337021506 19 May 2022 18:51:28 UTC (19 May 2022 20:51:28 CEST)
Unlock & cavity realignment
1337024342 19 May 2022 19:38:44 UTC (19 May 2022 21:38:44 CEST)
The matching improves very slightly, we decide to increase again the inner das up to ~710mW to see if we can find a value where the matching degrades:
1337027106 19 May 2022 20:24:48 UTC (19 May 2022 22:24:48 CEST)
We redo the scan on TEM00
1337027210 19 May 2022 20:26:32 UTC (19 May 2022 22:26:32 CEST)
Unlock & cavity realignment
1337028880 19 May 2022 20:54:22 UTC (19 May 2022 22:54:22 CEST)