A few further points, using the same methods as in the link above:
1) If H1 had the same jitter noise but the L1 coupling, things would be kind of alright for the current noise/power - see first plot.
2) Comparing to O1 couplings there are some interesting things... We did two tests, one in the beginning and one at the end, after Robert's work. The couplings and, as such, the DARM contributions, are vastly different, see second plot comparing the two injections. Something reduced the coupling between these two points, perhaps Robert's adjustment of IMC WFS offsets. Then it got big again in O2... If we could get to the coupling at the end of O1, life would be grand in psljitterland.
The third plot compares all three "states", beginning of O1, end of O1 and O2 in terms of ambient jitter as seen by IMC WFS A DC (in lock) and the coupling functions. Notice that there was something strange going on in the beginning of O1 with these signals, they show ridiculous 60 Hz harmonics - perhaps some grounding/wiring problem that was later fixed.
The fourth plot does the same comparison, but with the periscope motion (for completeness).
As far as L1 is concerned, we have the same coupling and approximately the same noise as in O1, so I'm not adding those plots here.
I suppose it's possible that H1 has always had jitter issues but they were not obvious (I definitely didn't appreciate the scale) ... until the noise was exacerbated by the HPO and the detector noise at higher power was low enough to see it.
One difference between O1 and O2 for H1 is the laser power. We are currently running with 30W input, whereas it was 22W for O1. One observation we made during the last commissioning period was that the coupling seemed strongly dependent on the initial alignment.
Robert, Valera, Anamaria
A few further points, using the same methods as in the link above:
1) If H1 had the same jitter noise but the L1 coupling, things would be kind of alright for the current noise/power - see first plot.
2) Comparing to O1 couplings there are some interesting things... We did two tests, one in the beginning and one at the end, after Robert's work. The couplings and, as such, the DARM contributions, are vastly different, see second plot comparing the two injections. Something reduced the coupling between these two points, perhaps Robert's adjustment of IMC WFS offsets. Then it got big again in O2... If we could get to the coupling at the end of O1, life would be grand in psljitterland.
The third plot compares all three "states", beginning of O1, end of O1 and O2 in terms of ambient jitter as seen by IMC WFS A DC (in lock) and the coupling functions. Notice that there was something strange going on in the beginning of O1 with these signals, they show ridiculous 60 Hz harmonics - perhaps some grounding/wiring problem that was later fixed.
The fourth plot does the same comparison, but with the periscope motion (for completeness).
As far as L1 is concerned, we have the same coupling and approximately the same noise as in O1, so I'm not adding those plots here.
I suppose it's possible that H1 has always had jitter issues but they were not obvious (I definitely didn't appreciate the scale) ... until the noise was exacerbated by the HPO and the detector noise at higher power was low enough to see it.
One difference between O1 and O2 for H1 is the laser power. We are currently running with 30W input, whereas it was 22W for O1. One observation we made during the last commissioning period was that the coupling seemed strongly dependent on the initial alignment.