With Hirata-san.

See pictures at the album PRM Remedying work after O3.

Summary: it seems possible to lower the mirror 6.3 mm using the SF, however, we need to do additional work becuase a couple of cables touch the security structure after a displacement of  3.3 mm from the SF setpoint.

We lowered the SF keystone below the current setpoint. The requirement was 6.3 mm plus an additional safety gap. However, we were only able to move it down by 3.3 mm before two cables underneath the BF touched the security structure.

We think we can fix this problem by doing the following:

• Modify one of the L-shaped security structure stops around the BF and
• Add a cable clamp underneath the BF; there is an unused M6 threaded hole next to the cables.

For the sake of checking, we lowered the SF keystone from the setpoint by approximately 7.3 mm and nothing else semeed to touch the security structure. A RM coil cable came very close to do it, but we can modify the security structure easily.