The longitudinal phase space distribution of electron beam plays critical role in ultra-short electron bunch production, coherent radiation, free electron laser (FEL) and many other applications. Photocathode RF gun is capable of controlling not only the transverse emittance of electron beam, but also longitudinal emittance. The longitudinal phase space distribution of photoelectron beam was in...

The DARHT II accelerator uses a pulsed high current electron beam and Bremsstrahlung converter target to generate an intense x-ray source for radiography. For the past several years, we have been performing an investigation of the possible adverse effects of (1) backstreaming ion emission from the Bremsstrahlung converter target and (2) the interaction of the resultant plasma with the electron ...

This paper gives an extensive analytical and numerical characterization of the growth rate curves (imaginary frequency versus wavenumber) derived from the free electron laser dispersion relation for a warm relativistic electron beam propagating through a constantamplitude helical magnetic wiggler field. The electron beam is treated as infinite in transverse extent. A detailed mathematical analy...

This first stage experiment is a Proof-of-Principle to support our novel vacuum laser acceleration (VLA) theory, published previously. Simulations show that based on current experimental conditions at the Brookhaven National Laboratory Accelerator Test Facility (ATF), an electron beam with initial energy of 15 MeV can get net energy gain from an intense CO2 laser beam. The difference of electro...

The analytical studies show that the application of a small solenoidal magnetic field can drastically change the self-magnetic and self-electric fields of the beam pulse propagating in a background plasma. Theory predicts that when omega_{ce} approximately omega_{pe}beta_{b}, where omega_{ce} is the electron gyrofrequency, omega_{pe} is the electron plasma frequency, and beta_{b} is the ion-bea...

A self-consistent theory of the free electron laser instability is developed for a hollow electron beam propagating through an undulator (multiple mirror) magnetic field. The stability analysis is carried out within the framework of the linearized Vlasov-Maxwell equations. It is assumed that the beam is thin, with radial thickness much smaller than the mean beam radius, and that v/yb << 1, wher...

Much of the theory and experimentation concerning creation of a high-brightness electron beam from a photocathode, and then applying emittance compensation techniques, assumes that one must strive for a uniform density electron beam, having a cylindrical shape. On the other hand, this shape has large nonlinearities in the space-charge field profiles near the beam’s longitudinal extrema. These n...

We present the design and fabrication of a micrometer-scale electron gun for the implementation of ultrafast low-energy electron diffraction from surfaces. A multi-step process involving photolithography and focused-ion-beam nanostructuring is used to assemble and electrically contact the photoelectron gun, which consists of a nanotip photocathode in a Schottky geometry and an einzel lens for b...

The electron cloud (EC) can be formed in the beam pipe of a circular accelerator if the secondary emission yield (SEY) of the inner surface is larger than 1, and it can detrimentally affect the circulating beam. Understanding the underlying physics and defining the scaling laws of this effect is indispensable to steer the upgrade plans of the existing machines and the design of new ones. The si...