Recently there has been interest in the collective instability regime of the free electron laser (FEL) [ 1,2]. There is also some work on the collective regime appearing in the Russian literature [3,4]. Bonifacio, Narducci and Pellegrini [5] (referred to hereafter as BNP) have discussed the collective instability regime of an FEL studying the growth of the radiation field from noise and the sat...

This paper describes development and initial results for a small prototype superconducting undulator with a period less than 1 cm, referred to here as a “supermini” undulator. The development of superconducting mini-undulators started in the early 1990s with work at BNL and KIT (Germany). In 1998, KIT demonstrated the first photon production with a super-mini of 3.8 mm period length [1]. This s...

The baseline specifications of European XFEL give a range of wavelengths between 0.1 nm and 2 nm. This wavelength range at fixed electron beam energy of 17.5 GeV can be covered by operating the SASE FEL with three undulators which have different period and tunable gap. A study of the potential for the extending the spectral range accessible to the XFEL in the direction of longer wavelengths is ...

Generally, turn-to-turn power fluctuations of incoherent spontaneous synchrotron radiation in a storage ring depend on the 6D phase-space distribution electron bunch. In some cases, if only one parameter is unknown, this can be determined from measured magnitude these fluctuations. Letter, we report an absolute measurement (no free parameters or calibration) small vertical emittance (5--15 nm r...

Insertion devices are utilized at synchrotron radiation facilities around the world for their capability to provide a high-brilliance X-ray beam. APPLE-II type undulators are especially important for their capacity to switch between a variety of photon beam polarization states. A high-precision soft X-ray polarimeter has been used to investigate the polarization calibration of an APPLE-II undul...

The VISA (Visible to Infrared SASE Amplifier) SASE free electron laser has been successfully operated at the Accelerator Test Facility (ATF) at BNL. High gain and saturation were observed at 840 nm. We describe here the diagnostic system, experimental procedures and data reduction algorithms, as the FEL performance was measured along the length of the undulator. We also discuss selected spectra...

The pulse width of hard undulator radiation (32 ps width, energy 14 keV) was determined by intensity interferometry. The method, in combination with various x-ray monochromators, enables measurements to be taken over a wide range of time frames, from ns to fs. The applicable target includes measurements of ultrafast x-ray pulse widths from fourth generation synchrotron light sources.

Within the framework of Hilbert space theory, we have developed a maximum-power variational principle applicable to classical spontaneous radiation from prescribed classical harmonic current sources. A simple proof is summarized for the case of three-dimensional fields propagating in vacuum, and specialization to the case of paraxial optics is discussed. The techniques have been developed to mo...

We describe the status and initial commissioning of the Visible to Infrared SASE Ampli"er (VISA) experiment. VISA uses a strong focusing 4 m undulator, the Brookhaven National Laboratory ATF linac with an energy of 72 MeV, and a photoinjector electron source. The VISA fundamental radiation wavelength is near 800 nm and the power expected at saturation is near 60 MW. Power, angular and spectral ...

The self-amplified, spontaneous emission free-electron laser (SASE FEL) gain process is a collective instability which induces microbunching in the electron beam. Microbunching approaching unity at the fundamental FEL wavelength (845 nm), and its second harmonic, have been measured at the VISA FEL, at or near saturation. These measurements, which use the beam's coherent transition radiation (CT...