Göttingen 2025 – scientific programme

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AKBP: Arbeitskreis Beschleunigerphysik

AKBP 7: Novel Accelerator Concepts II and FELs

AKBP 7.8: Talk

Wednesday, April 2, 2025, 18:00–18:15, ZHG004

Beam-by-design pulse shaping for seeded Free-Electron Laser — •Andreas Thiel¹, Skirmantas Alisauskas², Margarit Asatrian¹, Giovanni Cirmi², Eugenio Ferrari², Ingmar Hartl², Wolfgang Hillert¹, Nhat-Phi Hoang², Tino Lang², Pardis Niknejadi², Lucas Schaper², and Jiaan Zheng² — ¹Universität Hamburg, Hamburg, Germany — ²Deutsches Elektronen-Synchrotron, Hamburg, Germany

External seeding offers significant improvements in the pulse properties of Free-Electron Lasers (FELs) compared to Self-Amplified Spontaneous Emission (SASE) FELs. Seeding techniques such as High-Gain Harmonic Generation (HGHG) and Echo-Enabled Harmonic Generation (EEHG) utilize seed lasers and dispersive beamline elements to structure the longitudinal phase space of the electron beam. This process creates a density modulation that initiates the FEL process. The coherence properties of the seed are transferred to the FEL output, enabling the production of fully coherent, narrowband radiation with enhanced stability at shorter wavelengths. At the FEL facility FLASH (DESY), the ongoing FLASH2020+ upgrade project includes the integration of external seeding at high repetition rates. A key component of this upgrade is the development of an advanced laser system (SLASH) to act as the seed source. We explore the use of pulse shaping on the seed laser to control the characteristics of the seeded FEL output. Here, we present initial results from a test of the pulse shaper on our laser system, along with numerical simulations that investigate the potential and limitations of generating custom-tailored FEL pulses.

Keywords: Free-Electron Laser; Seeding; EEHG; HGHG; Pulse Shaping