In the linear regime before saturation, we describe the statistical correlations in the narrow band chaotic output of the SASE FEL. At a fixed position along the undulator axis, we derive joint probability distributions for the intensity in the output pulse to have values 1 I and 2 I at times 1 t and 2 t , and for the spectral intensity to have values ~ 1 I and ~ 2 I at frequencies 1 ω and 2 ω ...

The design study of an FEL oscillator with a bandwidth of Aw/wo < 10has been carried out. In this conceptual design, a grating rhomb is used to suppress the sideband instability. The spectral evolution of the FEL has been simulated using a one-dimensional, time-dependent FEL code. The system parameters for the simulations are: electron beam energy 120MeV, current I = 50A, electron micropulse le...

We propose and analyze a regenerative-amplifier free-electron laser (FEL) to produce fully coherent, hard x-ray pulses. The method makes use of narrow-bandwidth Bragg crystals to form an x-ray feedback loop around a relatively short undulator. Self-amplified spontaneous emission (SASE) from the leading electron bunch in a bunch train is spectrally filtered by the Bragg reflectors and is brought...

The stochastic nature of the self-amplified spontaneous emission (SASE) process of free-electron lasers (FELs) effects pulse-to-pulse fluctuations of the radiation properties, such as the photon energy, which are determinative for processes of photon-matter interactions. Hence, SASE FEL sources pose a great challenge for scientific investigations, since experimenters need to obtain precise real...

Due to the stochastic nature of Self Amplified Spontaneous Emission (SASE) it is crucial to measure for single pulses the spectral characteristics of ultrashort pulses from the Vacuum-UV Free Electron Laser (VUV-FEL) at DESY. To meet this particular challenge, we have employed both photon and photoelectron spectroscopy. Each FEL pulse is composed of an intense and spectrally complex fundamental...

SwissFEL is the Free Electron Laser (FEL) facility under construction at the Paul Scherrer institute (PSI), aiming to provide users with X-ray pulses of lengths down to 2 femtoseconds at standard operation. The measurement of the length of the FEL pulses and their arrival time relative to the experimental laser is crucial for the pump-probe experiments carried out in such facilities. This work ...

This paper derives, in closed form, the Green function of an FEL operating in the strongly Raman regime. This Green function allows for the calculation of the temporal and spatial evolution of an arbitrary input radiation pulse. For the first time superradiance, originally studied in Compton regime by Bonifacio and co-workers [Phys. Rev. Lett. 73 (1994) 70; Nucl. Instr. and Meth. A 239 (1985) 3...

BACKGROUND Although asthma is strongly associated with immediate hypersensitivity to indoor allergens, several studies have suggested that a cat in the house can decrease the risk of asthma. We investigated the immune response to cat and mite allergens, and asthma among children with a wide range of allergen exposure. METHODS We did a population-based cross-sectional study of children (aged 1...

The complex dications in the cooperative spin-crossover compound [FeL(2)][BF(4)](2) (2,6-di(pyrazol-1-yl)pyridine) pack through pi-pi interactions into a 2-D layered structure (a "terpyridine embrace" motif). The effects of doping the larger ClO(4)(-) ion into this lattice have been investigated. The bulk solids [FeL(2)][ClO(4)](x)[BF(4)](2-x) are isostructural with [FeL(2)][BF(4)](2) when x = ...