Swiss FEL Exchange Meeting Machine report Week 382020

Swiss. FEL Exchange Meeting Machine report Week 38/2020 Didier Voulot SEM, 21 September 2020

Week overview

Aramis Scale to 7. 5 ke. V: 300 u. J DRPS Reload 12 ke. V settings for Alvra SINXB failure S 10 CB 04 regulation Reload 7. 5 ke. V settings DRPS Athos MD Maloja request lower pulse energy! Athos MD BD studies

Beam set-up Mon-Tues • Restore the settings of last week with good lasing and transmission • The beam is mismatched in the LH but matching does not improve lasing, would need to do a full set-up • We chose to keep these settings and make minimal changes: • Correct laser profile (Athos) • Correct RF bucket and rephase full machine • Check bunch 2 STEP settings • After each step we check lasing in both branches • Final parameters: Aramis 12 ke. V 425 u. J, Athos 1. 5 m. J 540 e. V • Scale Aramis to from 12 to 7. 5 ke. V we get 300 u. J only (eventually 450 u. J after tuning and PSICO)

MD Wed-Thu (separate slides) Athos undulator commissioning (C. Kittel) • Commissioning of Athos MCP (SATFE 10 -PSRD 066) • Undulator alignment with spontaneous radiation • Investigate beam cutting in earlier undulators • Investigate shadow seen on MCP Beam dynamics studies Athos (E. Prat, A. Malzyhenkov, S. Reiche) • Set-up at 870 e. V, gain length measurements • Commissioning of passive dechirpers • Optics investigations • First short-pulse studies with Athos, using post-undulator passive streaker as diagnostics.

DRPS • • Monday: • An automatic performance check was started automatically after 400 days. • The check was done in the shutdown but this was not registered. (Maybe the timer reset was not down or not taken into account. ) • The performance check cannot be done while the machine is running. The dose should be low. So all detectors failed the check and raised an alarm. Tuesday: • The data sent by the detectors is not recognized by the data storage. Or some invalid data is sent. This causes the detectors to switch off and the neighbors to adjust their alarm thresholds. Which leads to an overdose alarm. • In some cases the DRPS buffer has to be reinitialized. This implies very low thresholds for 4 h => set-up very difficult. • Some data validity checks were temporarily removed, with SU monitoring the data. • Thursday visit of the DRPS (data storage) supplier-> outcome? • Fortunately two days reserved for set-up, from Wednesday on the system was running stably

Bunch 2 charge feedback • Bunch 2 charge is influenced by the presence of bunch 1, this is making the bunch 2/Mizar charge feedback unstable at certain rates • This is seen by the BPMs as well as the ICT: this is not a measurement artefact, bunch 2 has more charge without bunch 1 • Cathode effect?

Athos reported unstable beam after Aramis energy change Sunday afternoon, after AR energy change • Distorted and jittery beam on SATFE 10 -PSCR 066 • Some horizontal jitter also observed on SATBD 01 DSCR 210 • The beam looks elongated horizontally • Orbit stable (BPMs in STACL and BD) • Beam position and intensity in Athos GD unchanged Tuesday afternoon

Other issues SINXB 01: • 3 h downtime on Saturday • The fast current protection of the solenoid power supplies triggered an interlock. Interlock margin manually increased on the PLC. S 10 CB 04: • Unstable operation between Saturday midnight and Sunday morning. • The station did not reach full power because the BOC was not tuned properly. The wrong waveforms were used. We had to reboot the LLRF at the end to solve the problem. Undulator movers: • SATUN 22 and SATUN 15 occasionally getting stuck. Need local reset.

Conclusion • Parallel operation works well • Independent optimization (PSICO/manual tuning) • Parameter change (rate, pointing), some measurement (E-loss, orbit correction) • Small energy changes • Undulator scaling (Athos) or energy scaling (Aramis) • Working fine • Can be handled by the shift crew • Still difficult to make large energy changes or reload saved settings • Systematically lose pulse energy • Need manual retuning and/or PSICO