Summary:

I did an offline centroiding analysis of the HWS raw images and measured the thermal lens from the RH when 2W of power was applied. The measured thermal lens is consistent with the expected thermal lens using the nominal magnification of 7.5x for the HWS-Y sensor

Analysis:

I extracted the raw camera image files from times 1148010000 to 1148040000 from:

• controls@h1hwsmsr:~/framearchive/h1hwsmsr/ITMY/1148000000/

These were centroided offline to determine the spherical power as measured at the HWS surface. This value was converted to the single-pass thermal lens at ITMY by:

• dividing by a factor of 2 to convert from double-pass to single-pass
• dividing by (7.5)^2 to account for the nominal magnification between H1HWSY and H1-ITMY

The results are plotted together and show good qualitative agreement. There is probably room for a factor of 5%-10% variation in the RH SIM defocus response (micro-diopters per Watt). Also the RH SIM thermal lens doesn't account for an apparent time delay of about 10-20 minutes for the RH to warm up to full power.

Nevertheless, this measurement suggests that the H1HWSY is measuring correctly under this controlled circumstance.

The two channels plotted here are:

• H1:TCS-SIM_ITMY_SUB_DEFOCUS_RH_OUTPUT
• a proxy for H1:TCS-ITMY_HWS_PROBE_SPHERICAL_POWER (divided by 2).

Similar analyses for the HWS data from lock-acquistion and lock-loss are a little more difficult to interpret. This will be covered in a separate alog.

To Do:

1. Reset the HWS-Y reference centroids so the EPICS channel data is reliable.