LLRF'15 Workshop, Shanghai, Nov. 4, 2015 Low Level RF Control Implementation and Simultaneous Operation of Two Undulator Beamlines at FLASH V.Ayvazyan, S.Ackermann, J.Branlard, B.Faatz, M.Grecki, O.Hensler, S.Pfeiffer, H.Schlarb, C.Schmidt, M.Scholz, S.Schreiber, DESY, Hamburg, Germany; A.Piotrowski, Fast Logic, Lodz, Poland LLRF'15 Workshop, Shanghai, Nov. 4, 2015

Outline FLASH and the FLASH II project Layout of the facility Pulsed operation mode and timing aspects LLRF control for multi-beamlines Requirements and functionality extension Regulation performance Simultaneous operation and results Summary

Free-electron Laser in Hamburg - User Facility since 2005 TESLA type superconducting accelerating modules 1.3 GHz 3rd harmonic sc module 3.9 GHz FLASH1 fixed gap undulators FLASH1 Experimental Hall 315 m 5 MeV 150 MeV 1250 MeV Bunch Compressors 450 MeV Accelerating Structures RF Stations Lasers RF Gun Soft X-ray Undulators sFLASH FEL Experiments Photon Diagnostics Beam Dump THz FLASH1 FLASH2 Normal conducting 1.3 GHz RF gun Two photocathode lasers Extraction to FLASH2 FLASH2 variable gap undulators FLASH2 Experimental Hall

The FLASH II Project RF Control Requirements for Multi-Beamlines Separation of FLASH and FLASH2 beamlines behind the last accelerating module Tunability of FLASH2 by undulator gap change Extend user capacity with SASE (Self-Amplified Spontaneous Emission) RF Control Requirements for Multi-Beamlines Amplitude and phase can – in certain limits – be independently chosen for both FELs Ability of phase tuning at injector for variation in compression FLASH1 and FLASH2 Ability of gradient tuning of last two RF stations for wavelength scans Handling different beam loading scenarios Bunch repetition rate, number of bunches and charge

Temporal Structure (An Example) – Bunch charge FLASH1 – Bunch charge FLASH2 – RF signal (amplitude/phase) – Kicker amplitude filling FLASH1 transition FLASH2 decay 500 µs 500 µs 50 µs 250 µs 500 µs 98.2 ms t Kicker pulse: rise flattop fall Next pulse train SC machine 1 flattop, many bunches 100 ms,10 Hz Same optics setup for both beamlines, limitations of the bunch parameter range Energy acceptance in dispersive sections, slow magnet changes Two lasers operating on one cathode (alignment, orbit)

The Low Level RF System Overview In 2013 was the last major LLRF control hardware/software upgrade to a MicroTCA.4 based system Digital feedback - based on vector sum control group of cavities gradients MIMO controller Learning feed forward Beam based feedback Application software Description of the signal flow See talk by U. Mavric: Operational experience with the MicroTCA based LLRF system at FLASH

RF Control Functionality Extension for FLASH2 Main Timing RF Settings LLRF 3rd BL F1 F2 Kicker, BPM, BLM, MPS, Laser ctrl., … Transmission F1 Besides LLRF, all machine timing triggered systems receive a priori beam information => no manual synchronization LLRF control tables are generated from the operational setting according to the provided timing information Independent RF operational parameters adjustment (defined limits) F2 Globally controlled by main timing system, expected bunch pattern, start and stops Distribution to other subsystems Colored indications for all aspects Operator must be capable to distinguish Extandable for a 3rd beamline

RF Control Performance Vector-sum amplitude and phase stability fulfills given requirements min e for all t FB LFF We can achieve the given requirements on the Amplitude and phase stability Transition time is mainly determined by the kicker However there is space for improvements at the transitions steps, already smooth Kicker given minimum transition time can be achieved Smooth transition steps to avoid broadband excitation

Lasing with Two Independent Bunch Trains FLASH features two injector lasers to produce electron bunch trains with different numbers of bunches, charges and repetition rates It has been shown that for the same charge the same amount of SASE is present (top), while for different charges the difference in SASE is as theoretically expected (bottom)

First Lasing FLASH2 Most of the commissioning for FLASH2 was done in parallel with FLASH1 First lasing FLASH2: August 20, 2014 FLASH1 lasing in parallel 250 bunches with about 50 µJ First lasing FLASH2 was also first parallel operation After the demonstration of the first lasing at FLASH2 SASE operation was established at various wavelengths FLASH2: 1 bunch SASE Energy [µJ] FLASH1: 250 bunches FLASH: The first soft X-ray FEL operating two undulator beamlines simultaneously

Parallel SASE Operation Separate panels for FLASH1 and FLASH2 Fast kicker FLASH1 FLASH1 FLASH2 Two injector lasers FLASH2 SASE pulse energy (in a.u.) Two operators controlling two “virtual” machines Parameters affecting both BL are blocked from individual panels

Achieved Photon Wavelengths during Parallel SASE Operation Achieved photon wavelength during parallel SASE operation in the period from August 2014 to August 2015 Variable gap undulators in FLASH2 allow different photon wavelengths at fixed beam energies

Thanks for your attention! Summary and Outlook Low Level RF control functionality has been extended which makes simultaneous RF operation of multi-beamlines possible Can operate with different compressions, charges and bunch patterns Maintaining RF field amplitude and the phase stability requirements Achieved simultaneous operation and lasing of two undulator beamlines SASE operation at various wavelengths was established LLRF commissioning for multi-beamlines at European XFEL in progress Operations of alternating RF pulses (from pulse to pulse) Requires additional changes in firmware/software structure, e.g. extending the amount of control tables Thanks for your attention!