daniel.vander-hyde@LIGO.ORG - posted 23:45, Monday 15 October 2018 - last comment - 12:31, Tuesday 16 October 2018(44576)
TCS adjustments
Gabriele, Jenne, Shiela, Hang, Craig and Danny
- Today and yesterday there have been quite a few lock losses so Gabriele, Sheila, and myself looked at the trend data of the past day and noticed that there was a significant change in spherical power in the Hartmanns while transitioning from 2 watts to 20 watts that correlated to a decrease of the PRG and POP RF18 (please see first attached figure).
- Because ITMX HWS was so noisy, Gabriele wrote a python script that smooths out and overlaps all the changes in HWS ITMX and HWS ITMY right after transitioning to 20 watts and before losing lock (please see second attached figure).
- The spherical power should be held relatively constant throughout this transition which means that the TCS settings needed to be adjusted.
- To compensate for the approximately 15 microdiopter increase on ITMY, the ring heater power was increased by .7895 watts. The inverted ring heater step response was used to estimate this (please see last two figures). To compensate for the change in spherical power due to this ring heater change, CO2Y preheating needed to be adjusted and was increased by .6 watts.
- Guardian was getting angry when I changed the CO2Y preheating settings because the measured CO2 power was far off from the requested power. This is due to bad calibration in the rotation stage that manages the CO2 power delivered to ITM. I pressed the "search for home" button and it seems to have fixed this issue temporarily.
- The inverted RH step response method is being used to adjust the ring heater settings on work station zotws17 (should be running till 10-16-2018 6:00 pm PST).
- To compensate for the approximately 10 microdiopter decrease on ITMX, CO2X will only be reduced by .1 watts (from .5 watts to .4 watts) as we power up to 20 watts.
- Both CO2 power adjustments were determined by this CO2 actuation calibration
- To compensate for the approximately 15 microdiopter increase on ITMY, the ring heater power was increased by .7895 watts. The inverted ring heater step response was used to estimate this (please see last two figures). To compensate for the change in spherical power due to this ring heater change, CO2Y preheating needed to be adjusted and was increased by .6 watts.
- A large earthquake in New Caledonia at 2018-10-16 1:31:25 UTC prevented us from acquiring lock for the rest of the evening.
Images attached to this report
Comments related to this report
- Ring Heater script was turned off prematurely around gpstime 1223726510.
- The ITMY RH power is currently at 1.74 W (.87 W upper and .87 W lower) where it should have reached 1.85 W (.925 W upper and .925 W lower).
- As the RHs reach thermal equilibrium this .1 watt ring heater difference should equate to a 1.9 microdiopter difference in spherical power.
- The right heater power should be updated eventually but I'm hesitant to make any further ring heater changes right before we start locking again.