Tvo, Alexei, Dan
We took some more beam profiles of the single bounce (off of ITMX) IFO beam in HAM6 as the north door is off. We took measurements from the edge of the HAM6 table near the viewport and up to OM1. At first glance it seems the astigmatism of the IFO beam is not as bad as our previous measurements. However we still need to analyze the results. We don't have the OPO beam available at the moment so we couldn't profile that, perhaps we can before the doors go back on.
As we were there we also tried to profile the beam shape change induced by the SR3 heater. We got the heater up to ~70C and took profiles with the nanoscan in a single position near the HAM5 viewport. Along with the OMC mode scan results we took the other day we are hoping this will allow us to narrow down where in the beam parameter space we are. Results to come.
Attached is the analysis of the beam profiles taken 50.5'' from OM1 as the SR3 heater temperature increased from 30 to 75 C at 5 W requested power on the SR3 heater.
The starting beam size was (2401.2, 2375.6) um and the final size was (2310.5, 2258.7) um.
The ellipticity (1-b/a) of the beam varied from 0.01 to 0.02.
Attached is the analysis of the last set of data taken during this measurement.
Here the nanoscan was positioned 21' away from OM2, and the SR3 heater was left for about 15 minutes at 75 C to come to equilibrium.
The power to the SR3 heater was then cut and the beam size was tracked as the temperature decayed.
The aim of this exercise was to observe the optical transient of the SR3 by trying to find the point where the beam size would start changing after the power to the SR3 heater was cut.
20 minutes after the power was cut the beam size had not changed significantly and we stopped taking measurements.