Late Shift summary

Achievements:
- recovered the beam overlap
- changed lens position to have larger OL beam
- spatial overlap on YAG
- measured RIXS data delay scan at fixed photon energy

Problems:
- none

X-ray delivery
- 7.0 keV, up to 202 pulses at 564 kHz, 1.0 mJ.
- X-ray beam pointing changed at around 18:12 and it affects nano KB focus (from ~200nm to ~1um).

Optical laser delivery
- ns laser for jet illumination

Achievements/Observations
- Detector moved the most upstream position (~1.5 m sample to detector distance)
- BG measurement with water, buffer low salt
- Silver Behenate measurement for geometry file (mostly for detector distance)
- Data collection for different sample (pure) concentrations

X-ray delivery
- 7.0 keV, up to 202 pulses at 564 kHz, 1.0 mJ.
- Average pulse energy was about 1.9 mJ on Tuesday and Wednesday. It has to be discussed with BKR tomorrow morning.

Optical laser delivery
- ns laser for jet illumination

Achievements/Observations
- BG measurement with water, buffer low salt
- Lysozyme measurement for geometry file
- Data collection for six different sample concentrations [2 x 15 minutes runs]

Issues
- Pulse energy is very low as compared with Tuesday and Wednesday in this week.
- Damage found on IRU_SLIT4 Top and Bottom blades.
- NKB focus moved by ~20um at around 15:00 (during the handover period). SideMic X moved +20um to compensate it.

X-ray delivery

• 7.0 keV, up to 202 pulses at 564 kHz, 1.6-1.9 mJ.
• Average pulse energy tuned up to 1.9 mJ at 14:45, but slow continuous decay after that down to 1.7 mJ at the end of the shift.
• 45 minutes downtime in the morning and another 15 minutes to reset the IBFB later on, as coordinated by the PRC.

Optical laser delivery

• 800 nm, up to 202 pulses at 564 kHz.
• Large intensirty gradient through the burst compared to previous days. Recovered after moving the RF phase shifter. LAS informed.

Achievements/Observations

• Collected calibration and background data for upcoming user experiment.

X-ray delivery

• 7.0 keV, up to 202 pulses at 564 kHz, ~1.7 mJ.
• Number of pulses initially limited to 178. Promptly addressed by BKR.

Optical laser delivery

• 800 nm, up to 202 pulses at 564 kHz.
• Oscillating wavelength due to known faulty DMBCC stage, but otherwise stable delivery.

Achievements/Observations

• Aligned instrument and collected data with test samples as well as various background signals in preparation for next suer experiment.

Issues

• Changing the ROI of a Zyla appears to affect its timing.

X-ray delivery

• 6.0 keV, up to 202 pulses at 564 kHz 1.3-1.8 mJ.
• Decaying intensity through the day. Recovered once at 15:15 and slowly decaying again after that.

Optical laser delivery

• 770 nm, up to 202 pulses at 564 kHz and 101 at 282 kHz.
• Wavelength drift due to problem with BCC piezo stage. Mitigated by LAS.

Achievements/Observations

• Collected time-resolved diffraction from gold and gold-platinum nanorods/spheres at multiple laser fluences.

Issues

• Problem with the four ASICs in module Q2M1 of AGIPD could not be solved. Operated without those for today. Will be further investigated later on.

beam parameters: 2 colors at around 6.5 keV, 1 pulse

achievements:

user program continues with data acquisition at slightly varying photon energies (tens of eV both colors simultaneously) and at different delays between the colors

Issues:

• users have scheduled datasets to be measured overnight with larger delays up to 350 fs, however, the BKR was able to go only up to 100 fs delay despite having larger delays earlier in the experiment (even during nights)

X-ray delivery

• 6.0 keV, up to 202 pulses at 564 kHz, 1.8-1.9 mJ.
• Stable delivery except for downtime at start of shift (until 7:15) and two more hours in the morning.

Optical laser delivery

• 770 nm, up to 202 pulses at 564 kHz.
• Stable delivery.

Achievements/Observations

• Collected time-resolved diffraction from gold and gold-platinum nanorods at multiple laser fluences.

Issues

• Vacuum spike in EHU_PSLIT section.
• DAMNIT backend process stuck. A couple of Maxwell nodes were unaccessible. Solved by DOC and DA OCD.
• Issue with two AGIPD modules noticed around 21:20. Could not be recovered before end of the shift. To be further investigated tomorrow morning.

We asked the machine for two color mode in the morning. Tuning gave good results at first (1.6mJ second color, 100uJ first color), but as soon as any of the colors was switched off and on again the pulse energy dropped (~600uJ) and BKR had to retune to even get a fraction of the pulse energy back back. The same happened when changing the delay

X-ray delivery

• 6.0 keV, up to 202 pulses at 564 kHz and 101 at 282 kHz, 0.8-1.6 mJ
• Low pulse energy after beam handover. Improved around 10:00.
• ~1.5 hour downtime due to issue with A5.
• Several timing jumps of up to 1.5 ps visible on BAM and confirmed by X-ray/optical laser timing measurement at the instrument.

Optical laser delivery

• 770 nm, up to 202 pulses at 564 kHz and 101 at 282 kHz.
• Stable delivery.

Achievements/Observations.

• Collected time-resolved diffraction from gold and gold-platinum nanorods at multiple laser fluences and over long and short delay scans.

Issues

• AGIPD interlocked overnight and again during the morning due to temperature.
• Had to perform timing measurement and correction multiple times throughout the day due to timing jumps.

Today in the afternoon, SASE1 was tuned (a description of the activities in att 4). We now realize that this has in some form changed the SQS pulse parameters.

att 1 shows ion spectra recorded under nominally the same photon parameters before (run 177) and after (run 247)

it's also visible in the history of the SASE viewer that the behavior of the SASE3 pulse energy is different before and after 15:45, which is right when SASE1 was tuned. it clearly started fluctuating more. however, we don't think that the pulse energy fluctuations themselves are the reason for the large change in our data, we rather suspect a change in the pulse duration and/or the source point to cause this. however, we have no means to characterize this now after the fact.

it is particularly unfortunate that the tuning happened exactly BEFORE we started recording a set of reference spectra on the SASE3 spectrometer, which were supposed to serve as a calibration for the spectral corelation analysis to determine the group duration, as well as for a training data set to use the PES with machine learning as a virtual spectrometer for the large data set taken in the shifts before.

We fine tuned geometry parameters for linear effects on X motion (parallel offset) for all three mirrors.

dTz was corrected for M2 and M3 to -6.5mm (same geometry)

dTz was corrected for M1 to +6mm

for M2 we were able to do a parabola scan Y motion to check for lrTz

lrTz was then corrected to -433mm

correction in the same direction for M3 did not yield better results

Final mirror positions at HED - see picture

Laser status:

After the laser issues listed in https://in.xfel.eu/elog/OPERATION-2024/99 the late shift was finally able to find a timing setting for the amplifier trigger that was beyond stable settings under usual conditions, but which allowed to continue taking data runs for the rest of the beamtime reliably. The users were already able to reveal indications of a pump-probe signal in their data.

The issue itself remains but didn't show up in form of unstabilities anymore. After the beamtime LAS took some effort to investigate and narrow down to either a faulty trigger going into the front-end amplifier or on the front-end amplifier itself. To the best of our knowledge this circumstance will need to involve EEE support or even a service from the manufacturer and cannot be solved solely by LAS. LAS ensured that the highest priority will be to deliver stable laser pulses for next week's beamtime as well.

FEL status:

we found the FEL poynting to be very stable troughout the last weeks beamtime (despite some short down-times), which allowed to reliably verify the spatial overlap.

X-ray delivery

• 11.56 keV, 1-197 pulses @ 564 kHz, 2.6 mJ.

Optical laser delivery

• No PP laser output after shift change.

Achievements/Observations

• Collected static SFX data.

Issues

• Unavailability of PP laser prevented collection of TR-SFX data, which was the main goal of the shift.

EPS issue for Transmissive imager SA1 (OTRC.2615.T9) w.r.t Operation eLog #96

The motor screen positions w.r.t. the EPS switches had been realigned (last Wednesday 8th May), tested today (14th May) and the EPS is again enabled for the different beam modes. All is back to normal.

X-ray delivery

• 11.56 keV, 1-197 pulses @ 564 kHz, 2.4-3.1 mJ.
• Beam down a bit over 1 hour due to accelerator interlock problem.

Optical laser delivery

• 840 nm, 50 fs, 50 pulses @ 141 kHz.
• Stable delivery.

Achievements/Observations

• PP laser timed.
• Completed TR-SFX dataset at 30 ps delay.

Issues

• Scantool stuck in ACQUIRING state. Recovered by restarting the device.
• HIREX data missing for most of the night. GOTTHARD II control and receiver devices found down in the morning. Server on which they are reunning appears to have crashed at 1:36. DOC informed in the morning.

Weekend summary:

Overall stable beam delivery with 300bunches @18keV and 750uJ

-issue with XGM on Saturday night/morning

-The intensity in SA2 over the train is dropping of when SA3 is changing some parameters. BKR can fix it within a couple of minutes

-The users found suitable working conditions to overcome the limitations from the 10bar He supply line.