Millimeter-wave FEL-oscillator is one of a possible source of RF power for accelerating structures of future linear colliders with high energy gain. JINR-IAP collaboration develops a high-efficiency single-mode FEL-oscillator with a Bragg resonator and reversed guide field. Output power of 48 MW at the frequency of 30.6 GHz with spectrum width 0.25% was registered in recent experiments using in...

Here we describe a Linac, driven by a Traveling Laser Focus (TLF), arranged with the help of a special deflecting device. This Linac has an accelerating structure, which is open from one side. The laser radiation is focused from this side onto a spot with minimal transverse dimensions. This spot is moved by a fast deflecting device in synchronism with the instantaneous position of the charged p...

X-ray microanalyses of sub-micrometer features require that a lower accelerating voltage be used. This reduction in the accelerating voltage reduces the penetrating distance of the beam electrons and thereby reduces the analytical volume. Two general strategies have been proposed for achieving the smallest analytical volume. The first approach involves significantly reducing the accelerating vo...

High frequency linear collider schemes envisage the use of rather high accelerating gradients: 50 to 100 MV/m for Xband and 80 MV/m for CLIC. Because these gradients are well above those commonly used in accelerators, high gradient studies of high frequency structures have been initiated and test facilities have been constructed at KEK [1], SLAC [2] and CERN [3]. The studies seek to demonstrate...

We consider means to damp the wake-field left behind ultra-relativistic charges. In particular, we focus on a pair of travelling wave accelerators operating at an X-band frequency of 11.424 GHz. In order to maximize the efficiency of acceleration, in the context of a linear collider, multiple bunches of charged particles are accelerated within a given pulse of the electromagnetic field. The wak...

Experiments are reported on inverse free-electron-laser acceleration, including for the first time observations of the energy change as a function of relative injection phase of the electron bunches. The microwave accelerating structure consists of a uniform circular waveguide with a helical wiggler and an axial magnetic field. Acceleration of the entire beam by 6% is seen for 6 MeV electron bu...

The existence of future horizons in spacetime geometries poses serious problems for string theory and quantum field theories. The observation that the expansion of the universe is accelerating has recently been shown to lead to a crisis for the mathematical formalism of string and M-theories, since the existence of a future horizon for an eternally accelerating universe does not allow the formu...

We discuss the obstacles for defining a set of observable quantities analogous to an S-matrix which are needed to formulate string theory in an accelerating universe. We show that the quintessence models with the equations of state −1 < w < −1/3 have future horizons and may be no better suited to an S-matrix or S-vector description. We also show that in a class of theories with a stable supersy...

Since its inception in the early 1980s, the field of plasma-based particle accelerators has made remarkable advances. Robust plasma accelerating structures can now be excited over centimeter scales using short laser pulses and over meter scales using ultrarelativistic particle beams. Accelerating fields in excess of tens of GV/m can be sustained over these lengths. Laser-driven plasma accelerat...

,pABSTRACT . . . . Expressions for accelerating structure parameters, including those that determine the peak and average power inputs required to attain a given gradient, are given as functions of aperture to wavelength ratio for a 2aj3 mode disk-loaded guide. The value of the wavelength to aperture ratio varies over a large range, corresponding to group velocities that vary from nearly zero t...