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AdV-SBE (MultiSAS for SPRB, SDB2, SIB2 commissioning)
H.J. Bulten - 23:36 Wednesday 01 July 2020 (49036) Print this report
SBD2 tracking check
As agreed during the AdV onsite meeting from yesterday June 30, I today tried to add tracking to SDB2 to see how well it performs. Unfortunately, I could not get all necessary channels done in the control, so instead of adding the differential channel for the superattenuator filter 0 I made a test channel, called tracktest, that made a sine wave of 0.06 Hz at an amplitude of 1 micrometer and let the topstage of SDB2 track that. In the second half of the test, I made the amplitude 0. Since the witness channel is the difference between tracktest and the bench, whereas the control is on the topstage, I think that this is an instructive test.

I am still analyzing the results; report will follow tomorrow. I understood that tomorrow the power will be switched off the crates, so I hurried to get the data. The current version of the SBE_SDB2.cfg config file has many extra channels to add the tracking of the tower but at the moment I track 0 (so same as no tracking); the changes I made in the config file should have no effect. I need more time to finalize this; I will give an update later this week.
Comments to this report:
bulten - 11:01 Monday 06 July 2020 (49043) Print this report
Alain Masserot kindly added the Superattenuator signals to the SDB2 processes, so I could track Sa_OB_F0_x and z.
This I did; the SDB2 bench performs just as well as the SNEB bench.
In the files added to this report I show the z-position of the SDB1 Filter-0 stage, and the filter-0 z position of the SDB2 minitower,
as well as the witness signal which is computed from the LVDTs reading out the SDB2 bench and the SDB1 bench.
When tracking is on, the top filter of the minitower tracks the top filter of the output bench (Sa_OB, SDB1), and the differential speed between
the SBD2 and SDB1 benches is becoming much smaller in the 0.1-0.5 Hz region, the region that during bad weather causes
scattered light noise.

In the second plot I show the RMS of the differential LVDT-readings of the benches and the tracking status. One can observe that the
RMS is reduced when tracking is on. In the SNEB bench, scattered light is causing sensitivity limitations if during bad weather the
RMS is above ~ 2; here for SDB2 the RMS is well below that value.
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