SA1 Beckhoff issue

SA1 blocked to max. 2 bunches and SA3 limited to max 29 bunches
At 9h46, SA1 goes down to single bunch. PRC is called because SA3 (SCS) cannot get the required >300 bunches anymore. (at 9h36 SA3 was limited to 29 bunches/train)

FXE, SCS, DOC are informed, DOC and PRC identify that this is a SA1 Beckhoff problem.
Many MDLs in SA1 are red across the board, e.g. SRA, FLT, Mirror motors. Actual hardware state cannot be known and no movement possible.
Therefore, EEE-OCD is called in. They check and identify out-of-order PLC crates of the SASE1 EPS and MOV loops.
Vacuum and VAC PLC seems unaffected. 

EEE-OCD needs access to tunnel XTD2. It could be a fast access if it is only a blown fuse in an EPS crate.
This will however require to decouple the North branch, stop entire beam operation for SA1 and SA3.
Anyhow, SCS confirms to PRC that 29 bunches are not enough for them and FXE also cannot go on with only 1 bunch, effectively it is a downtime for both instruments.

Additional oddity: there is still one pulse per train delivered to SA1 / FXE, but there is no pulse energy in it ! XGM detects one bunch but with <10uJ.
Unclear why, PRC, FXE, and BKR looking into it until EEE will go into the tunnel.

In order not to ground the magnets in XTD2, a person from MPC / DESY has to accompany the EEE-OCD person.
This is organized and they will meet at XHE3 to enter XTD2 from there.

VAC-OCD is also aware and checking their systems and on standby to accompany to the tunnel if required.
For the moment it looks that the SA1 vacuum system and its Beckhoff controls are ok and not affected.

11h22: SA3 beam delivery is stopped.
In preparation of the access the North branch is decoupled. SA2 is not affected, normal operation.

11h45 : Details on SA1 control status. Following (Beckhoff-related) devices are in ERROR:

• SA1_XTD2_VAC/SWITCH/SA1_PNACT_CLOSE and SA1_XTD2_VAC/SWITCH/SA1_PNACT_OPEN (this limits bunch numbers in SA1 and SA3 by EPS interlock)
• SA1_XTD2_MIRR-1/MOTOR/HMTX and HMTY and HMRY, but not HMRX and HMRZ
• SA1_XTD2_MIRR-2/MOTOR/* (all of them)
• SA1_XTD2_FLT/MOTOR/
• SA1_XTD2_IMGTR/SWITCH/*
• SA1_XTD2_PSLIT/TSENS/* but not SA1_XTD2_PSLIT/MOTOR/*
• more ...

12h03 Actual physical access to XTD2 has begun (team entering).

12h25: the EPS loop errors are resolved, FLT, SRA, IMGTR, PNACT all ok. Motors still in error.

12h27: the MOTORs are now also ok.

The root causes and failures will be described in detail by the EEE experts, here only in brief:
Two PLC crates lost communication to the PLC system. Fuses were ok. These crates had to be power cycled locally.
Now the communication is re-established, and the devices on EPS as well as MOV loop have recovered and are out of ERROR.

12h35: PRC and DOC checked the previously affected SA1 devices and all looks good, team is leaving the tunnel.

13h00: Another / still a problem: FLT motor issues (related to EPS). This component is now blocking EPS. EEE and device experts working on it in the control system. They find that they again need to go to the tunnel.

13h40 EEE-OCD is at the SA1 XTD2 rack 1.01 and it smells burnt. Checking fuses and power supplies of the Beckhoff crates.

14h: The SRA motors and FLT are both depending on this Beckhoff control.
EEE decides to remove the defective Beckhoff motor terminal because voltage is still delivered and there is the danger that it will start burning.

We proceed with the help of the colleagues in the tunnel and the device expert to manually move the FLT manipulator to the graphite position,
and looking at the operation plan photon energies it can stay there until the WMP.

At the same time we manually check the SRA slits, the motors are running ok. However, removing that Beckhoff terminal also disables the SRA slits.
It would require a spare controller from the labs, thus we decide in the interest of going back to operation to move on without being able to move the SRA slits.

14h22 Beam is back on. Immediately we test that SA3 can go to 100 bunches - OK. At 14h28 they go to 384 bunches. OK. Handover to SCS team.

14h30 Realignment of SA1 beam. When inserting IMGFEL to check if the SRA slits are clipping the beam or not, it is found after some tests with the beamline attenuators and the other scintillators that there is a damage spot on the YAG ! See next logbook entry and ATT#3. This is not on the graphite filter or on the attenuators or in the beam as we initially suspected.
The OCD colleagues from DESY-MPC and EEE are released.
The SRA slits are not clipping now. The beam is aligned to the handover position by RC/BKR. Beam handover to FXE team around 15h.