Exponential Gain and Saturation of a Self-Amplified Spontaneous Emission Free-Electron Laser

Abstract

Self-amplified spontaneous emission in a free-electron laser has been proposed for the generation of very high brightness coherent x-rays. This process involves passing a high-energy, high-charge, short-pulse, low-energy-spread, and low-emittance electron beam through the periodic magnetic field of a long series of high-quality undulator magnets. The radiation produced grows exponentially in intensity until it reaches a saturation point. We report on the demonstration of self-amplified spontaneous emission gain, exponential growth, and saturation at visible (530 nanometers) and ultraviolet (385 nanometers) wavelengths. Good agreement between theory and simulation indicates that scaling to much shorter wavelengths may be possible. These results confirm the physics behind the self-amplified spontaneous emission process and forward the development of an operational x-ray free-electron laser.

Operation of a free-electron laser from the extreme ultraviolet to the water window

“…In September 2000, a group at Argonne National Laboratory (ANL) became the first to demonstrate saturation in a visible (390 nm) SASE FEL (11). Soon after, in September 2001, a group at DESY (Hamburg, Germany) demonstrated lasing to saturation deep into the vacuum-UV at 98 nm (12,13).…”

Lasers à électrons libres de courtes longueurs d'onde : état de l'art et perspectives

“…Un des points les plus délicats reste le canon à électrons : l'extraction des électrons se fait non plus par chauffage mais par excitation avec un faisceau laser intense et les électrons sont accélérés à l'aide d'un champ radiofréquence de gradient élevé (50 MeV/m). Après l'observation de la saturation du SASE dans l'infra-rouge proche [2l], LEULT (Argonne, USA) l'a obtenue à 530 et 385 nm [22], TESLA-TTP (DESY, Allemagne) dans la gamme 125-85 nm [23] et DUVFEL (Brokhaven) à 400 nm [24]. D'autres projets sont en cours : SLAC (Stanford, USA) SCSS (Spring-8, Japon) ou en discussions : à Bessy (Allemagne), en Suède et en Italie.…”

The Physics and Properties of Free-Electron Lasers

“…In Table 1, we present some of the fundamental parameters for four proof-ofprinciple SASE experiments which have been carried out over the last few years in the visible and vacuum ultraviolet: TTF1 at DESY [37]; LEUTL at ANL [38]; VISA at BNL [39]; and DUV-FEL at BNL [40]. The parameters correspond to reported experiments and do not necessarily represent the best or shortest wavelength performance achieved to-date.…”