With the CITF locked and the SPRB under drift control (using the B4_QD2 112 MHz signals, see Fig.1), we checked the centering of the EPRB diaphragms. We adjusted very finely their position and close the diaphragms at minimum aperture to have a good reference for the PC alignment during the afternoon shift.

When this check was done, the SPRB angular position was the following : TX = 152 urad, TY = -655.5 urad.

Then we put the ITF in NI single bounce, and we checked that for the same angular position given by the SPRB LVDT, the B4 beam was still passing through the EPRB diaphragms.

In addition we recorded a picture of the two B4 cameras in single bounce: see attached file.

For B4_Cam1, the gaussian fit parameters are: wx = 334 um and wy = 705 um.