Speaker
Description
High repetition-rate, short wavelength and fully coherent free electron lasers can open up new possibilities in research frontiers in high-resolution serial coherent diffraction imaging and time-resolved ultrafast spectroscopies. At present, soft x-ray external seeded FELs can hardly reach over 10 kHz repetition-rate due to the limited external seed laser power. In our recent experiment, we demonstrated the first lasing and stable operation of a direct amplification enabled harmonic generation free electron laser. In which a rather weak initial ultraviolet seed laser of only ~3 MW peak power was employed and amplified several tens of times in a long modulator. Together the electron beam was highly energy modulated and later was converted into density modulation in the dispersion section. Effective microbunching was then formed and coherent high harmonic radiation up to the 12th harmonic of the seed laser was then obtained in the following radiator. We also successfully achieved the saturated FEL lasing at the 7th harmonic. DEHG-FEL has been demonstrated as a robust external seeded FEL mode which can significantly reduce the required seed laser power and hence enable high repetition-rate operation. And it’s particularly suitable for seeding with short-wavelength high-order harmonic generation pulses from noble gases to extend soft x-ray external seeded FELs to new wavelength domains.
Footnotes
*Z. Qi et al., Phys. Rev. Lett. 135, 035001 (2025)
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