In preparation for locking with the new BBSS, I have taken an inventory of the beamsplitter filters to note where various notches and bandstops are located by suspension stage.

As a reminder, Oli copied over much of the BSFM filters into the BBSS model, 90154.

M1: none as far as I can tell

M2:

• M2 LOCK L: Violin modes, butterfly mode
  • need to be measured and replaced, can wait until IFO lock
• M2 LOCK P and Y: FM5 BS bounce/roll, FM7 QUAD bounce/roll
• M2 OLDAMP P: FM5 BS bounce/roll, FM6 20 Hz bandstop
  • what is this 20 Hz bandstop for? can we turn it off?
• M2 OLDAMP Y: FM5 BS bounce/roll

M3:

• M3 LOCK P and Y: FM6 28.45 Hz notch
  • tracked down to alog 43968
  • can we turn this off?

Ibrahim and Oli have measured the BBSS bounce and roll modes to be at 19.80 Hz and 32.09 Hz respectively, 90319.

I'm replacing the bounce and roll bandstops on M2 LOCK and OLDAMP to be centered around these frequencies.

Old foton design string for "NotBR_BS":

ellip("BandStop",4,1.5,40,17.7,17.9)ellip("BandStop",4,3,40,25.7,26.4)gain(1.6788)

New foton design string for "NotBR_BBS":

ellip("BandStop",4,1.5,40,19.7,19.9)ellip("BandStop",4,3,40,32,32.2)gain(1.6788)

As a final note, I'm not sure how necessary the BR bandstops are if we have dampers, so we could consider not having any on at all.