aLIGO LHO Logbook

H1 INJ (CAL, INJ)

evan.goetz@LIGO.ORG - posted 14:53, Wednesday 25 May 2016 - last comment - 16:01, Thursday 26 May 2016(27383)

Updated PINJ_TRANSIENT / PINJ_HARDWARE filters

Transitioning over to the new, improved inverse actuation filters (see LHO aLOG 27176), I removed the old filters from PINJ_HARDWARE and installed the new inverse actuation filters into the PINJ_TRANSIENT bank. Since the CW injections will apply the inverse actuation function to condition their signals before sending it to the PINJ path, we don't want the filters in PINJ_HARDWARE any longer.

CW injections are running right now using this new actuation function. Keith R. and I made a test of this earlier to verify the output was roughly correct (Keith will post an aLOG about our work). He wants to see this running over the next few days to gain confidence that the injections are operating normally.

Comments related to this report

evan.goetz@LIGO.ORG - 16:34, Wednesday 25 May 2016 (27395)CAL, INJ

Link

Reference to Keith's aLOG regarding today's CW injection test.

Attached is a comparison of the old and new inverse actuation filters. Note the discrepancy at low frequencies because the old version assumed only a free-mass response instead of the real force-to-length suspension model. Also, different approximations were made at high frequencies leading to different magnitude and phase effects. Recall the new filter is valid within 5% in magnitude and 5 degrees in phase up to 2 kHz, when taking into account that waveforms must have an assumed 200 us advance.

Non-image files attached to this comment

comparison.pdf

evan.goetz@LIGO.ORG - 16:01, Thursday 26 May 2016 (27410)CAL, INJ

Link

Keith R. noticed that the CW injections appeared to be ~10% smaller in amplitude now that they are no longer passing through the old inverse actuation filter. To see if the new design is the cause, I plotted the inverse actuation transfer function in Foton and plotted the results of the old/new. Note that there is also an old AI2 filter module that didn't appear to be in-use lately. In any case, I plot all three curves in the attached plot.

Importantly, the inverse actuation transfer function is larger in magitude for the Old version compared to the New version by about 10% at 2 kHz. Meanwhile the Old w AI2 is smaller than the New version. This difference is the likely explanation to Keith's observation.

Non-image files attached to this comment

comparison2.pdf