Rasmus Ischebeck

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Inverse-Designed Narrowband THz Radiator for Ultrarelativistic Electrons

Rasmus Ischebeck, Benedikt Hermann

THz radiation finds various applications in science and technology. Pump-probe experiments at free-electron lasers typically rely on THz radiation generated by optical rectification of ultrafast laser pulses in electro-optic crystals. A compact and cost-efficient alternative is offered by the Smith-Purcell effect: a charged particle beam passes a periodic structure and generates synchronous radiation. Here, we employ the technique of photonic inverse design to optimize a structure for Smith-Purcell radiation at a single wavelength from ultrarelativistic electrons. The resulting design is highly resonant and emits narrowbandly. Experiments with a 3D-printed model for a wavelength of 900 mu m show coherent enhancement. The versatility of inverse design offers a simple adaption of the structure to other electron energies or radiation wavelengths. This approach could advance beam-based THz generation for a wide range of applications.

AMER CHEMICAL SOC2022

A compact and cost-effective hard X-ray free-electron laser driven by a high-brightness and low-energy electron beam

Majed Chergui, Leonid Rivkin, Rasmus Ischebeck, Mike Seidel, Paolo Craievich, Christoph Peter Hauri, Paul Beaud, Christopher Alexander Arrell, Giulia Fulvia Mancini, Camila Bacellar Cases Da Silveira, Eugenio Ferrari, Thomas Schmidt, Thomas Schietinger, Sven Reiche, Lukas Stingelin

We present the first lasing results of SwissFEL, a hard X-ray free-electron laser (FEL) that recently came into operation at the Paul Scherrer Institute in Switzerland. SwissFEL is a very stable, compact and cost-effective X-ray FEL facility driven by a low-energy and ultra-low-emittance electron beam travelling through short-period undulators. It delivers stable hard X-ray FEL radiation at 1-A wavelength with pulse energies of more than 500 mu J, pulse durations of similar to 30 fs (root mean square) and spectral bandwidth below the per-mil level. Using special configurations, we have produced pulses shorter than 1 fs and, in a different set-up, broadband radiation with an unprecedented bandwidth of similar to 2%. The extremely small emittance demonstrated at SwissFEL paves the way for even more compact and affordable hard X-ray FELs, potentially boosting the number of facilities worldwide and thereby expanding the population of the scientific community that has access to X-ray FEL radiation.

NATURE RESEARCH2020

Proof-of-principle e+ source for future colliders

Inverse-Designed Narrowband THz Radiator for Ultrarelativistic Electrons

A compact and cost-effective hard X-ray free-electron laser driven by a high-brightness and low-energy electron beam

Inverse-Designed Narrowband THz Radiator for Ultrarelativistic Electrons

Proof-of-principle e+ source for future colliders

A compact and cost-effective hard X-ray free-electron laser driven by a high-brightness and low-energy electron beam