(Temporary) solution for the vacuum incident in SA1

This morning at 7h18 the vacuum interlock of SA1 closed the beamline valves and thus stopped the XFEL beam delivery for SA1 and SA3.
The reason was a real vacuum problem, with vacuum pressure critically rising in the SA1_XTD2_ATT solid attenuator.
Thanks to VAC-OCD and a workaround it was possible to re-establish beam operation SA1/SA3 already by 8h50, but the problem is not fixed !

History data shows that movements of ATT progressively deteriorated the vacuum since FRI 3.11.2023 morning.
At the moment it is stabilized at a high level, but any further significant deterioration of the vacuum level in ATT would make a tunnel intervention unavoidable.

A vacuum work intervention in the tunnel will cause a beam delivery downtime for SA1/SA3 of at least 5 hours
as we know from a similar previous cases(*). This including an extensive XTD2 undulator tunnel search,
which is required because this cannot happen as ZZ but interlock must be broken.

In order to protect the user beamtimes in SA1 (SPB/SFX) and SA3 (SQS),
the following is necessary and agreed by the coordinators (PRC+RC) and VAC:

1) It is not allowed to move ATT until VAC has repaired the leak (PRC has locked the device)
2) VAC group will enter XTD2 after the user beamtimes end on monday, and will work on removing the vacuum leak. This will affect the FD studies scheduled for monday.
3) SPB confirms that they can work in the current (OUT) state of the XTD2 attenuator
4) If FXE (in-house beamtime) cannot work with these same conditions as SPB/SFX (ATT out), then the FXE beamtime is cancelled
5) FXE is requested to contact PRC by phone