I've added a block to the TCS model to estimate the real-time thermal lenses in each of the test masses and the surface curvature of each of the test masses.
OPTIC_LENS.mdl
The main new library block, shown in the attached figure, is OPTIC_LENS which takes as inputs:
- Ring heater power
- CO2 laser power (N/A for ETMs)
- IFO ARM power (calculated from H1:ASC-TR_X_B_SUM_OUTPUT and H1:ASC-YTR_X_B_SUM_OUTPUT)
- Also, the estimated surface absorption of the optic
Each of these inputs goes into a filter that contains (or will contain) the transfer function for power to diopters for that specific actuation. These are:
- H1:TCS-ITMX_SIM_SUB_DEFOCUS_RH (single-pass substrate thermal lens from the ring heater)
- H1:TCS-ITMX_SIM_SUB_DEFOCUS_CO2 (single-pass substrate thermal lens from the CO2 laser)
- H1:TCS-ITMX_SIM_SUB_DEFOCUS_SELF (single-pass substrate thermal lens from self heating)
- H1:TCS-ITMX_SIM_SUB_DEFOCUS_STATIC (single-pass substrate static lens from construction)
- H1:TCS-ITMX_SIM_SURF_DEFOCUS_RH (single-pass surface lens from RH: inverse of the ROC change from the RH)
- H1:TCS-ITMX_SIM_SURF_DEFOCUS_SELF (single-pass surface lens from self heating: inverse of the ROC change from self heating)
- H1:TCS-ITMX_SIM_SURF_ROC_NOM (nominal ROC of the optic)
which are summed together to yield. These are outputs for the model:
- H1:TCS-ITMX_SIM_SUB_DEFOCUS_FULL_SINGLE_PASS: the total single pass thermal lens in diopters
- H1:TCS-ITMX_SIM_SURF_DEFOCUS_FULL (the inverse of the current ROC, including thermal effects)
- H1:TCS-ITMX_SIM_SURF_ROC_FULL (the current ROC, including thermal effects)
h1tcscs.mdl
There are four of these blocks in the main TCS model h1tcscs.mdl - one for each test mass. Although the ETMs contain inputs for CO2 lasers, these are grounded. See the attached figure.
The outputs from the four blocks are currently terminated. I plan on updating the model to create channels for COMMON and DIFFERENTIAL MICHELSON and ARM lenses and others, as required. This will be after I've verified that the model and filters are all working correctly.
