SwissFEL - first lasing at a wavelength of 4.1 nm

SwissFEL first Lasing at a wavelength of 4.1 nm

The electron beam energy of SwissFEL was recently increased to above 900 MeV by successfully bringing two new accelerating modules into operation. This allowed SwissFEL to produce laser radiation for the first time in the soft x-ray regime with a photon wavelength of 4.1 nm. During the next months, the electron beam energy will be progressively further increased with the goal of enabling first user experiments at a wavelength of around 0.5 nm towards the end of this year.

On Friday December 2nd at 1am SwissFEL observed for the first time FEL lasing in the undulator line. The lasing was achieved with a commission beam of low intensity, repetition rate and energy, i.e. 100pC/bunch, 1Hz and 377MeV. The 12 undulators were set to a K value of 1.2. The resulting wavelength computed from beam energy and undulator K value is 24nm. The FEL signal was observed with a Si-diode detector. The spontaneous radiation signal with uncompressed electron beam increased by a large factor when the beam was compressed from 10ps to about 1ps at constant charge and electron beam energy. By opening the undulator gaps a first FEL gain curve was measured.