This morning (Dec 10th) we investigated the impact of the angular setpoints of the suspended benches (SNEB, SWEB, SPRB) on the sensitivity.
We started by recentering the B7 and B8 beams on the SNEB/SWEB camera by adjusting the bench setpoints.
The SWEB angular setpoints were adjusted between 09h10 and 09h15 utc. Initially the SWEB setpoints were TX = +100 urad, TY = 1795 urad. After the recentering on the camera the new setpoints are TX = +90 urad, TY = +1810 urad.
The SNEB angular setpoints were adjusted between 09h18 and 09h21 utc. Initially the SNEB setpoints were TX = -695 urad, TY = -75 urad. After the recentering on the camera the new setpoints are TX = -673 urad, TY = -75 urad.
We tested various angular positions of SWEB around its new setpoints. For each tested position, we took some data with a low frequency line (0.1 Hz) injected at the level of the suspension top stage to move the bench along the Z degree of freedom in order to be able to evaluate the scattered light coupling factor (data will be analyzed off-line). All measurements were performed with the bench tracking loop ON, unless otherwise specified:
1/ SWEB TY scan:
- SWEB TY = 1815 urad (+5 urad) reached at 09h28m20
09h33m54 Started line injection with amp=50
09h35m05 Started line injection with amp=100 (bench moving by ~+/-20 um)
09h37m36 Line switched off
- SWEB TY = 1820 urad (+10 urad) reached at 09h38m25
09h39m29 Started line injection with amp = 100
09h41m30 Line switched off
- SWEB TY = 1810 urad (0 urad) reached at 09h42m25
09h43m49 Started line injection with amp = 100
09h45m53 Line switched off
- SWEB TY = 1805 urad (-5 urad) reached at 09h46m30
09h48m18 Started line injection with amp = 100
09h50m40 Line switched off
- SWEB TY = 1800 urad (-10 urad) reached at 09h51m05
09h52m19 Started line injection with amp = 100 Warning : glitch in the data. Situation back to normal at 09h53m48
09h55m39 Line switched off
- SWEB TY = 1795 urad (-15 urad) reached at 09h56m10
09h58m14 Started line injection with amp = 100
10h00m37 Line switched off
- SWEB TY = 1810 urad (0 urad) reached at 10h02m15
- SWEB TY = 1805 urad (-5 urad) reached at 10h04m05
- SWEB TY = 1810 urad (0 urad) reached at 10h06m10
2/ SWEB TX scan:
- SWEB TX = 95 urad (+5 urad) reached at 10h07m25
10h08m42 Started line injection with amp = 100
10h10m43 Line switched off
- SWEB TX = 100 urad (+10 urad) reached at 10h11m15
10h12m37 Started line injection with amp = 100
10h14m41 Line switched off
- SWEB TX = 105 urad (+15 urad) reached at 10h15m35
10h16m47 Started line injection with amp = 100
10h18m49 Line switched off
- SWEB TX = 90 urad (0) reached at 10h19m25
- SWEB TX = 85 urad (-5 urad) reached at 10h21m20
10h23m23 Started line injection with amp = 100
10h25m45 Line switched off
- SWEB TX = 80 urad (-10 urad) reaced at 10h26m10
10h27m18 Started line injection with amp = 100
10h30m19 Line switched off
- SWEB TX = 75 urad (-15 urad) reached at 10h31m00
10h32m44 Started line injection with amp = 100
10h35m39 Line switched off
- SWEB TX = 80 urad (-10 urad) reached at 10h36m00
- SWEB TX = 90 urad (0 urad) reached at 10h38m40
10h40m09 Started line injection with amp = 100
Opening tracking loop at 10h42m18
10h44m29 Line switched off
Closing tracking loop at 10h46m48
We tested various angular positions of the SPRB bench. Its initial setpoints were TX = 170, TY = -600 urad:
- SPRB TY = -595 (-5 urad) reached at 10h55m30
- ITF unlocked at 11h01m40 (fast unlock)
- ITF relocked in low noise 3 at 12h30 utc
- SPRB TX = 170, TY = -595 at 12h44m00
- SPRB TX = 170, TY = -590 at 12h45m30
- SPRB TX = 165, TY = -590 at 12h49m00
- SPRB TX = 160, TY = -590 at 12h51m00
- SPRB TX = 175, TY = -590 at 12h53m10
- SPRB TX = 180, TY = -590 at 12h55m00
- ITF unlocked at 12h56m11
- SPRB setpoints put back at TX = +170, TY = -595.
At first look it seems that the position TY=-590, TX=165 was a bit better then other positions, to be confirmed after deeper analysis.