sheila.dwyer@LIGO.ORG - posted 15:58, Thursday 15 May 2025 - last comment - 16:44, Tuesday 03 June 2025(84419)
SR3 heater on overnight
TJ, Camilla, Sheila
TJ and Camilla got the HWSs working, and now we turned on the SR3 heater at 15:54 UTC, 2W requested power. This is to do a check of the SR3 heater calibration and range similar to 27262
Comments related to this report
camilla.compton@LIGO.ORG - 10:53, Tuesday 20 May 2025 (84481)
Looking at when this test was done at LLO, the lens changing happened over a period of three hours and the lens power increased in the same direction on both HWS, so its possible our HWS are not a good witness for the SR3 curvature change.
jennifer.wright@LIGO.ORG - 10:25, Tuesday 03 June 2025 (84746)
Aidan calculated 2.45 uD/W at LLO, and we get 9.44 uD/W (from the H1:TCS-ITM{Y,X}_HWS_PROBE_SPHERICAL_POWER trends with an estimated noise of 4.48e-12uD/W.
camilla.compton@LIGO.ORG - 11:43, Tuesday 03 June 2025 (84751)
Looked closer at these HWS signals during SR3 heater heat up and cool down. In all these plots, the two t-cursors are used as the reference and shown HWS live image.
Cool down plot attached (ITMX was misaligned so there's no HWS data)
Some strange things:
ITMX heat up ndscope spherical power looks the opposite direction of ITMY, this isn't physical. Looking at the HWS Live plot, this isn't really want's happening, it appears that the SR3 signal just appears if the edge of ITMX is heating up so the center that the calculations are made from isn't correct, making the calculated spherical power wrong.
In both the heat up and cool down of the ITMY signal, there appears to be two steps with a flat region in the middle. Looking at the the flat region only, attached, it appears that the spherical power is continuing to change in the expected direction, unsure why this change isn't shown in the calculated spherical power.
Images attached to this comment
jennifer.wright@LIGO.ORG - 11:54, Tuesday 03 June 2025 (84753)
With the numbers from ITMY HWS only, and looking at the 3hr 11 m cooldown in Camilla's photo, the lens change is 6.68e-6 Dioptres/W taking into account that the HWS beam passes twice through SR3.
jennifer.wright@LIGO.ORG - 16:44, Tuesday 03 June 2025 (84768)
SR3 heating up can be seen on the HWS signals but is not particulatly clear, see attached.
Looking at when this test was done at LLO, the lens changing happened over a period of three hours and the lens power increased in the same direction on both HWS, so its possible our HWS are not a good witness for the SR3 curvature change.
Aidan calculated 2.45 uD/W at LLO, and we get 9.44 uD/W (from the H1:TCS-ITM{Y,X}_HWS_PROBE_SPHERICAL_POWER trends with an estimated noise of 4.48e-12uD/W.
Looked closer at these HWS signals during SR3 heater heat up and cool down. In all these plots, the two t-cursors are used as the reference and shown HWS live image.
Some strange things:
With the numbers from ITMY HWS only, and looking at the 3hr 11 m cooldown in Camilla's photo, the lens change is 6.68e-6 Dioptres/W taking into account that the HWS beam passes twice through SR3.
After talking with Camilla, she reminded me the change in RoC (delta R) =/= 2/(delta D),
where D is defocus (1/focal length).
but instead delta R = 2/(2/R + delta D) - R
Where R=36.013m is given in https://git.ligo.org/IFOsim/ligo-commissioning-modeling/-/blob/main/LHO/yaml/lho_O4.yaml?ref_type=heads
delta R comes out as 4.3mm +/- 0.18 mm (which is the same order of magnitude as the change Aidan measured in alog #27262 at LLO).
The error was estimated from looking at the noise on the spherical power and propagating through the calculation of delta R.