We report for the first time to our knowledge the experimental achievement of storage ring free-electron laser (FEL) oscillations on the third harmonic in the wide infrared region. The FELs were oscillated in the wavelength regions of 852-881 nm and 1510-1551 nm. The measured linewidth of the third-harmonic FEL was narrower than that of the fundamental FEL owing to the narrower spectral width o...

We propose a simple method to significantly enhance the temporal coherence and spectral brightness of a self-amplified spontaneous emission (SASE) free-electron laser (FEL). In this purified SASE (pSASE) FEL, a few undulator sections (called slippage-boosted section) resonant at a subharmonic of the FEL radiation are used in the middle stage of the exponential growth regime to amplify the radia...

Numerical simulation codes are basic tools for designing Free Electron Lasers (FEL). They are used to study the impact of di!erent parameters, e.g. wiggler errors and external focusing, which allow FEL users to optimize the performance. For faster execution some simulation codes assume radial symmetry or decompose the radiation "eld into a few azimuthal modes, although then this treatment does ...

Exponential growth and superradiance regimes in a high-gain free electron laser (FEL) are studied in this paper for both a seeded FEL and a Self-Amplified Spontaneous Emission (SASE) FEL. The results are compared to the earlier superrdaince theory and the recent experimental observation. The influence of an initial energy chirp along the electron bunch on the superradiance mode is explored for ...

BACKGROUND The major cat allergen, Fel d 1, is a tetrameric glycoprotein composed of 2 heterodimers. Polymorphisms in this allergen are well documented. Recent work shows that Fel d 1 samples can contain core fragments of variable immunoreactivity. OBJECTIVES Our objective was to compare Fel d 1 polymorphism in cat extracts and house dust, which is used as an indicator of allergen exposure an...

Harmonic lasing is a possible mode of operation of X-ray FEL user facilities that allows us to provide brilliant beams of higher energy photons for user experiments. Another useful application of harmonic lasing is the so-called harmonic lasing self-seeded free electron laser (HLSS FEL) that allows the improvement of spectral brightness of these facilities. In the past, harmonic lasing has been...

The intensity of undulator radiation, not amplified by the FEL interaction, can be larger than the maximum FEL signal in the case of an X-ray FEL. In the commissioning of a SASE FEL it is essential to extract an amplified signal early to diagnose eventual misalignment of undulator modules or errors in the undulator field strength. We developed a numerical code to calculate the radiation pattern...

Using the recently proposed echo-enabled harmonic generation (EEHG) free-electron laser (FEL) scheme, it is shown that operating the Shanghai deep ultraviolet FEL (SDUV-FEL) with single-stage to higher harmonics is very promising, with higher frequency up-conversion efficiency, higher harmonic selectivity and lower power requirement of the seed laser. The considerations on a proof-of-principle ...