hugo.paris@LIGO.ORG - posted 09:43, Monday 12 August 2013 (7411)
HAM6-ISI - HEPI can be unlocked
The transfer functions measured recently on HAM6-ISI featured a discrepancy between what was seen by GS13-V2 (purple curve), and what GS13-v1 (cyan) and GS13-V3 (yellow) would see.
Thinking GS13-V2 could be saturating, we tried taking a new set of measurements over the weekend, with lower actuation. Reducing the actuation did not change the shape of HAM6-ISI TF, as seen on the latest results.
The transfer function measured with the CPSs show a good match between the corners, and confirm the good functioning of the platform, themselves, and the actuators.
I extracted the GS13 responses out of the TF measured on HAM6-ISI over the weekend. GS13-V2 has its resonance pretty low (~15%, blue curve) compared to what we usually see (red curve). This is what caused the discrepancy we saw.
Nothing alarming though. The sensor works fine, even in the worse configuration (see spectra with ISI tilted).
Moreover, the symmetrization filters we apply into the readout chain are maid to account for mismatch in GS13 resonance frequency. I made a quick set of symmetrization filters. Once symmetrized the TF feature a good match between the corners (see HAM6-ISI Symmetrized TF).
HAM6-HEPI can be unlocked.
Images attached to this report
