Ultrafast time-resolved electron diffraction based on a photocathode rf electron gun is being developed in Osaka University to reveal the hidden dynamics of intricate molecular and atomic processes in materials. The photocathode rf gun generates a femtosecond-bunch electron beam by femtosecond laser driving. The transverse emittance, bunch length and energy spread were measured. The growths of ...

An analytic theory of cumulative multibunch beam breakup in linear colliders is developed. Included is a linear variation of transverse focusing across the bunch train as might be applied, e.g., by chirping the radio frequency power sources or by using radio frequency quadrupole magnets. The focusing variation saturates the exponential growth of the beam breakup and establishes an algebraic dec...

A relativistic bunch moving in the vicinity of a dielectric slab excites Cerenkov radiation. The spectrum of this radiation depends on the dielectric coefficient, the energy of the bunch and its geometric shape. If the dielectric slab is active and the bunch excites the proper frequency, the wake will be amplified. In the framework of a linear theory we discuss the dependence the spatial growth...

We report on measurements of the bunch energy spectrum at the end of the SLAC linac. Using the spectra obtained for two different linac rf phases we obtain both the bunch induced voltage and the longitudinal distribution of the bunch. The measurement results are compared with theoretical predictions. In particular, the induced voltage is in good agreement with that obtained using the calculated...

We present a technique for the design and verification of efficient bunch-by-bunch controllers for damping longitudinal multibunch instabilities. The controllers attempt to optimize the use of available feedback amplifier power one of the most expensive components of a feedback system and define the limits of closed loop system performance. Our design technique alternates between analytic compu...

The end effect in a bunched beam is caused by the space-charge forces, which accelerate particles at the bunch head and decelerate particles at the bunch tail. It occurs in high-current linear accelerators and rings [1]. In the University of Maryland Electron Ring (UMER) project [2,3,4], the energy of particles at the very ends of a rectangular bunch is 15% different from that of the main part ...

The effect of ultrafast electron beam bunch dynamics on single shot electro-optic sampling detection schemes is examined. It is shown that ultrashort electron bunch fields of adequate magnitude can dynamically impose additional bandwidth on laser probe pulses. The significance of this effect is evaluated by comparing the dynamics of the laser probe to that of the nonradiative field of a single ...

In this article we study effects of microbunch cooperative electromagnetic radiation in a bend on transverse beam dynamics. An overtaking radiative interaction between different parts of the bunch results in three major forces variable along the bunch. Longitudinal force leads to energy loss and causes the bunch emittance growth in the bend due to the dispersion effect. Radial force consists of...

Electron bunches with charge densities ρ of the order of 102 to 103 [nC/cm3], energies between 20. and 100. [MeV], peak current > 100 [A], bunch lengths between 0.3 and 1.8 [cm], and bunch charge of 2.0 to 20. [nC] are relevant to the design of Free Electron Lasers and future linear colliders. In this paper we present the results of numerical simulations performed with a particle in a cell (pic...

With the high intensity, low emittance beams needed to reach the luminosity goals of the linear collider, beam size monitoring will play an important role in machine operation. In the damping rings synchrotron radiation (SR) emitted by the bunch can provide a means of measuring transverse bunch size and shape. With suitable imaging and high speed detection of the SR, bunch size, shape, and posi...