We implemented on SWEB the modifications in order to handle 40 W of input power:
- with the bench suspended in air, we added some masses and both the angular and the position controls have been properly closed, after having recentered the suspension;
- at the beginning we were not able to find any flash on B7 camera and photodiode, even if the mirrors have been realigned in the last good working point;
- Paolo reminded that, venting the minitower and the corresponding pipe, induces a tilt on the long tower;
- tilting about 25 urad in TX the end mirror allowed us to recover flashes and the lock of the North arm;
- the lock of the cavity was working properly also in reflection on B4;
- at 14 UTC some minutes of clean data have been acquired to have reference positions on B7 camera;
- we blocked the bench to install/replace/remove the following components:
- SNEB_M1: mirror replacement -> V213 -> W218 (R = 0.20, arrow: horizontal, on the right looking att he mirror, pointing on West);
- SNEB_M2: mirror replacement -> V212 -> AdV206 (R = 0.85, arrow: horizontal, on the right looking att he mirror, pointing on East);
- SNEB_M3: new mirror installation -> AdV238 (R = 0.97, arrow: horizontal, on the right looking att he mirror, pointing on West);
- SNEB_Mmot4: mirror replacement V214 -> AdV205 (R = 0.85, arrow: horizontal, on the right looking att he mirror, pointing on East);
- a new beam dump on the reflection of SNEB_M3 has been installed;
- B7_PD1 and B7_PD2 have been swapped (now Airbox 29 in reflection and airbox 30 in transmission);
- new absorbing glasses have been added on the two B7 photodiodes;
- one large counterweight has been removed;
- the small absorbing glass used to dump the reflection of B7_QD2 has been removed;
- the large absorbing glass used to dump the reflection of B7_QD2 has been replaced between QD2 and M3;
- two counterweights have been added.
- we unblocked the bench and we balanced it;
- both angular and position loops have been properly closed;
- we updated the configuration file and the offsets of the two photodiodes;
- we roughly aligned the beam on B7_PD1 and B7_PD2.
In the following table the mass of installed and removed components is listed:
|Added mass (g)||Removed mass (g)|
|Mirror mount SNEB_M3 + M4 screw||235.6|
|Mirror SNEB_M3 R = 0.2||47.3|
|New beam dump||310.3|
|Counter weight + screw||934.6|
|Two clamps for beam dump + screws||120|
|One QPD beam dump + screws||176.9|
|One counter weight + screw||353.6|
|One counter weight + screw||88.4|
|Two PD beam dumps||22.5|
- centering of the B7 camera;
- alignment of the beam on B7_QD2;
- alignment of the beam reflected by B7_QD2 on the proper beam dump;
- alignment of the beam reflected by SNEB_M3 on the new beam dump.
In hte attached picture the new mirror SNEB_M3 and the new beam dump are shown.
We profited of the intervention on SNEB to check also possible interferences on the bottom part of the mSAS and on the bench itself (possible sources of some of the troubles encountered in the last weeks):
- the LVDT connector of the filter 1 is free to move and is far from the shield (rubbing almost impossible);
- one large white cable on the bottom of the bench was rubbing against the exernal frame (it could be the source of rubbing solved slightly moving the bench along z).
Reminder for future interventions on SNEB and SWEB with the bech suspended in air: add a tilt of about 25 urad in TX to recover the proper alignment of the cavities.