stuart.aston@LIGO.ORG - posted 08:26, Tuesday 04 November 2014 - last comment - 00:30, Friday 12 December 2014(14729)
ITMX & ITMY (QUAD) M0-M0 Phase 3b undamped TFs (for Acceptance)
Initial attempts to take undamped TFs on ITMX & ITMY exhibited rung up P & R modes (see LHO aLOG entry 14653). For the next attempt, fine tuning of excitation amplitudes was necessary to avoid ringing up these modes. Phase 3b (in-vacuum) undamped TF measurements have been taken for ITMX & ITMY (QUAD) suspensions as follows:- - ITMX M0-M0 undamped results (2014-10-30_0700_H1SUSITMX_M0_ALL_TFs.pdf) - ITMX R0-R0 undamped results (2014-10-30_0700_H1SUSITMX_R0_ALL_TFs.pdf) - ITMY M0-M0 undamped results (2014-10-28_1200_H1SUSITMY_M0_ALL_TFs.pdf) - ITMY R0-R0 undamped results (2014-10-28_1200_H1SUSITMY_R0_ALL_TFs.pdf) ISI Status: ISI's damped and FULLY_ISOLATED via Guardian. ITMX & ITMY undamped TFs above have been compared with other similar QUADs at the same phase of testing (allquads_2014-10-30_AllQUADS_Doff_Phase3b_ALL_ZOOMED_TFs.pdf). The plot key is as follows:- Blue Trace = Model Prediction (fiber/thincp). Orange Trace = L1 ITMX (fiber 2013−09−04), Phase 3b. Black Trace = L1 ITMY (fiber 2013−09−05), Phase 3b. Magenta Trace = H1 ITMY (fiber 2014−10−28), Phase 3b. Cyan Trace = H1 ITMX (fiber 2014−10−30), Phase 3b. Summary: M0-M0, main chain TFs are a very good fit to the model, for all DOFs, with only some minor cross-couplings from P2V. R0-R0, reaction chain TFs agree with the model predictions and are consistent with similar QUADs. The largest deviation from the model can be seen with the ~1.45 Hz P mode, a consequence of the harness routing stiffening the suspension, seen before. Some minor cross-couplings are also present: from P2L, P2R, and P2V only for ITMY. Damped TFs should be taken to verify that damping loops suppress these cross-couplings. All data, scripts and plots have been committed to the sus svn as of this entry.
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Power spectra had been taken and processed a while back, but not posted until now. These power spectra measurements have been compared to previous Phase 3 measurements for H1 ITMs (allquads_2014-11-26_Phase3_H1ITMX_ALL_Spectra_D*.pdf). The plot key is as follows:- Black Dashed Line = Expected Sensor Noise Blue Trace = H1SUSITMY 2013−07−19_1400, Phase 3b (in-vacuum) Green Trace = H1SUSITMX 2014−04−11_1600, Phase 3b (in-vacuum) Red Trace = H1SUSITMX 2014−07−07_1000, Phase 3a (in-air) Summary: Noise floors for recent ITMX measurements are consistent with previous measurements, but are much more noisy below 40 Hz due to air turbulence, clean rooms, purge air etc. Oddly, L1 and L2 OSEM DOFs appear to suffer from a scaling problem. However, scaling is correct for L1 & L2 EULER DOFs. n.b. the same discrepancy was also observed in the data taken before the optic was swapped. Thus, raising no concerns. All data, scripts and plots have been committed to the sus svn as of this entry.
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Damped transfer functions can be found in LHO aLOG 15575.