Reports until 02:47, Monday 11 May 2026
H1 SUS (SUS)
thomas.roocke@LIGO.ORG - posted 02:47, Monday 11 May 2026 (90194)
Attempt at QOSEM Test on BSFM

[Tom R, Oli]

Summary: QOSEM testing on the BSFM will require the tablecloth to be shifted OR SUSP to be raised, probably not worth the effort to do so given the BBSS will be ready for QOSEMs shortly.

Last Friday Oli and I attempted to install the QOSEMs onto the now removed from chamber and on test stand BSFM suspension, now that the IAS work was completed. The purpose of this test is to run and compare TFs taken with QOSEMs, providing a final functionality test before installation on the BBSS (which is not yet ready to accept QOSEMs). The full test and integration plan for the QOSEMs / BBSS can be found here T2600169.

We began by removing the SD BOSEM from M1 of the BSFM, and swapping the flag out for the QOSEM variety. We installed the QOSEM onto the cage, and used the existing DB25 in vac extensions and in air cables to run the QOSEM to its sat amp in SUS-R2. The QOSEM and its entire signal chain was functional, with readouts from this SD QOSEM appearing as expected in CDS. 

Unfortunately upon unlocking the suspension, to align this SD QOSEM, we found that its y axis could not be brought into range with the cams (at its best was ~1mm off). This is a similar issues we faced when setting up the BBSS at LLO. As the SD BOSEM does not have a readout in this 'y' or vertical direction, misplacement of the tablecloth by ~1mm is unnoticeable, and does not impede function of the BOSEMs, but as we are activity trying to readout this axis it does matter for the QOSEM.

As such, to setup the QOSEMs on the BSFM, we would need to raise the tablecloth, or SUSP via the blade spring angle. While this certainly could be done, at the moment this feels like an unnecessary amount of work to do for a quick test of the QOSEMs, given the BBSS will be ready shortly. For now we have abandoned this test, and removed the SD QOSEM from the BSFM, reinstalling the original BOSEM.