matthewrichard.todd@LIGO.ORG - posted 18:08, Tuesday 05 March 2024 - last comment - 15:18, Wednesday 06 March 2024(76137)
Updating OMCscan to reflect transition to OMC001
Matthew, Jennie W, Gabriele
In the initialization of the OMCscan code (which gets OMC scan data, analyzes it and then plots it), I updated several values to reflect the transition from OMC003 to OMC001, so that omc analyses are accurately done. For example, several small changes include:
- FSR -> 264.97 MHz
- Finesse --> 426.96
- TMSv --> 58.05 MHz
- TMSh --> 57.94 MHz
- PZT2response --> 6.435 MHz/V (this change is from 5.9 MHz/V, which is puzzling because the previous PZT2response [12.73 nm/V] is quite close to the new one [12.92 nm/V])
The values were obtained from T1500060 Table 19, which report the OMC optical test results for OMC001; note: the conversion from nm/V to MHz/V is found by the relation delta(f)/f = delta(L)/L, where delta(L) is 2*PZTresponse in nm/V, L is the round-trip cavity length, and f is 1064nm converted to MHz
Are we sure that the previous OMC used OMC's "PZT2" (12.7nm/V) for the scan, not OMC's "PZT1" (11.3nm/V)?
I mean: there is a possibility that the indication of PZT2 on the screen may not mean PZT2 on the OMC.
Also the response of the PZT is nonlinear and hysteretic.
I'd rather believe the frequency calibration using the cavity peaks (e.g. FSR/Modulation freqs) than the table top calibration of the PZTs.
Good suggestion!
Computing the PZT response from the FSRs we get around 6.3 MHz/V.
And on your note about certainty of using PZT2 response, I am not sure.
I think we usually used the channel PZT2 to perform scans with OMC 003. But yeah, I am not sure if this corresponds to PZT2 on the real OMC. The PZT calibration we just use in the scan analysis to get an initial guess for the calibration but the final calibrated scan does indeed find the carrier 00 and 45 MHz 00 peaks to fit the non-linearity of the PZT.