Not sure if this is the cause of the fringes reported before, but at 5.6 keV there are clear cracks visible on the XTD2 Attenuators 75 umm and 150um CVD, see attached. There is also a little bit of damage on the 600 um CVD, but not as strong as the others.

At 5.6 keV we will need to use the thin attenuators. I will mention again in case this causes problems downstream.

Edit 8:50h: We do not observe additional interference effects in the downstream beam profile (see attachement 4)

5.61 keV setpoint in SA1 was confirmed to correspond to 5.660 keV (+/- 0.003 keV), see attached.

The user expt #5644 can proceed as planned.

Preparation for user experiment transient grating, Cris Svetina

• Used 7.12 keV from ACC with very good performance, above 4 mJ
• Got spatiotemporal overlap with transient gratings using monochromatic beam
• One issue solved by DOC: Picomotors could not be scanned in karabacon, even though this worked well two/three weeks ago

User experiment transient grating, Cris Svetina. (LTP)

• Used 7.12 keV from ACC with very good performance, above 4 mJ.
• Collected pump-probe data on user sample
• Sudden timing jump of around 20 ps. Could not find out why this happened some time between 9h today and 18h.
• Needed to add camera to DAQ. Solved this on instrument side using the DAQ assistant. Great tool!

User experiment transient grating, Cris Svetina. (LTP)

• Used 7.11 keV from ACC with very good performance, above 4 mJ.
• Collected pump-probe data on user sample most of the time today, only minor interruptions due to accelerator outages
• After the outage at 21h, SASE came back with 17 eV lower photon energy, so we had to re-calibrate the undulator spectrum
• FXE will operate in 24h mode for the rest of the delivery week

User experiment transient grating, Cris Svetina. (LTP)

• Used 7.11 keV from ACC with very good performance, above 4 mJ.
• Collected pump-probe data on user sample most of the time today
• FXE will operate in 24h mode for the rest of the delivery week

Measurements to check the impact of bunch compression on FXE mono transmission were successful. We could change the peak current between 4 and 12 kA and saw changes in bandwidth between 17 and 100 eV (at 14 keV). Results are under evaluation.

SA1 brought to safe state:

• CRLs moved out
• Mono moved out
• CVDs in XTD2 ATT inserted
• PBLM-based feedback was started and kept running to avoid beam drifting off of M3
• Hirex shutter closed
• The M1/M2 offset was decreased a bit as compared to saturday mornings' value (was very close to total reflection limit and to safely use 100 bunches, it was decreased to be on the safe side). Should not affect further measurements for XFELO on sunday.

Used 9.4 keV with 94 kHz wed and thu nights. Received approx. 0.9 mJ with large fluctuations in pulse energy, however acceptable for the tasks below.

Achievements:

• X-ray optics and goniometer aligned for next user experiment 5725
• Transmission through Mono #2 recovered and calibrated to match Mono #1
• Understood uneven beam profile of FXE PI originating from the thick XTD2 ATT CVDs. Without them, the beam looks nice.
• Observed that overbending M2 gives better beam profile than underbending under the present conditions

Issues encountered:

• Major issue: M3 RY piezo actuator not working any more. This means beam feedback cannot run and beam keeps drifting off on the instrument apertures. This cannot be compensated by M2 piezo due to the small aperture of M3. The issue was reported wednesday night to PRC, XRO and FXE group and is being worked on by XRO
• One limit switch was found swapped; fixed by FXE engineers
• Some motors moved in the opposite direction as compared to previous commissioning, even though parameters were saved and restored. Not understood, but was easy to work around.

We observe a continuous horizontal beam drift in SA1 after the M1 incident. It seems not to converge, so one can wonder where this will go....

Attached screenshot shows the M2 piezo actuator RY that keeps the beam at the same position on the M3 PBLM. These are about 130 m apart, The drift is 1V/12 hours. 0.01V corresponds to a beam motion by 35 um. So the drift velocity is 0.3 mm/hour. In the past days this had at least once lead to strong leakage around M2. But the two feedbacks in the FXE path are keeping the beam usable most of the time.

Finally, the drift velocity of the pointing reduced approx a factor of 2 as compared to yesterday, see attached. Possibly it will still converge...

FXE received the beam and did not change accelerator settings.

Beam alignment to FXE was re-established using the new values for the old M1/M2 offset.

Monochromator aligned to the SPB energy setpoint.

THz source aligned to Xrays and several reference positions for Xray pointing taken. Further steps require THz radiation, which is not available at this point.

Xrays realigned back to SPB XTD9 screen.

The xray beam drifted significantly on wednesday and thursday (18. and 19.) but then was not drifting on friday (20.), see attached trendline of the M2 actuator that kept the beam at fixed position on M3.

Today also seems that beam pointing is stable. But unclear what happened earlier...

This is to report some findings during operation that should be looked into (mostly to avoid in the future, because both negatively affect data quality of the user expt at FXE):

• At the moment, the 99:1 mode affects 4 to 5 pulses out of 100 in SA1, see first screenshot that shows in the top right the IPM reading with each blue point denoting the average pulse energy in a train. This was not always the case. After initial setup on thursday it did affect only a single train out of 100.
• On 27.10., the switching of SA2 between 1 and multiple bunches affected SA1 beam heavily, see the jumps in SA1 pulse energy in the second screenshot shown here:
  • The pulse energy dropped by 15% and
  • the pointing changed vertically by 150 um on the FXE PI (data not shown, but available from karabo trendlines)

Edit 8.11.: Added screenshot (grafana/ctrend) to show that the vertical displacement was permanent (not corrected by the feedback)

We had some trouble with the DAQ. It was not able to start runs properly.

We got the following error messages:

initially:

[00:01:27]: Problem of communication with data manager

[00:01:30]: Start new run ...

[00:01:38]: Failed starting data recording

DM: error at registerRun (Request to MDC timeouted)

after trying to start the run again:

[00:05:35]: Start new run ...

[00:05:35]: Failed starting data recording

DM: error at registerRun (Problem of communication with MDC

#Info: MDC-1100: MDC web server error: Error creating run

#Details: {'run_number': ['must be unique per proposal', 'has already been taken'], 'experiment_id': ['has already been taken']})

Cycling the DAQ resolved the issue.