Short-range wakefields generated in the blowout regime of plasma-wakefield acceleration

In the past, calculation of wakefields generated by an electron bunch propagating in a plasma has been carried out in linear approximation, where the plasma perturbation can be assumed small and plasma equations of motion linearized. This approximation breaks down in the blowout regime where a high-density electron driver expels plasma electrons from its path and creates a cavity void of electrons in its wake. In this paper, we develop a technique that allows to calculate short-range longitudinal and transverse wakes generated by a witness bunch being accelerated inside the cavity. Our results can be used for studies of the beam loading and the hosing instability of the witness bunch in PWFA and LWFA

Wake and Impedance

A systematic exposition of the basic concepts of wakes and impedances is given for relativistic beams in accelerators.Comment: Lecture presented at JAS'2000 Accelerator School On Frontiers Of Accelerator Technology: High Quality Beams, St. Petersburg - Moscow, Russia, 1-7 July 200

A novel fast simulation technique for axisymmetric PWFA configurations in the blowout regime

In the blowout regime of plasma wakefield acceleration (PWFA), which is the most relevant configuration for current and future applications and experiments, the plasma flow that is excited by the ultra-relativistic drive beam is highly nonlinear. Thus, fast and accurate simulations codes are indispensable tools in the study of this extremely important problem. We have developed a novel algorithm that deals with the propagation of axisymmetric bunches of otherwise arbitrary profile through a cold plasma of uniform density. In contrast to the existing PWFA simulation tools, our code PLEBS (PLasma-Electron Beam Simulations) uses a new computational scheme which ensures that the transverse and longitudinal directions are completely decoupled---a feature which significantly enhances the speed and robustness of the new method. Our numerical results are benchmarked against the QuickPic code and excellent agreement is established between the two approaches. Moreover, our new technique provides a very convenient framework for studying issues such as beam loading and short-range wakefields within the plasma cavity

Microbunched Electron Cooling with Amplification Cascades

The Microbunched Electron Cooling (MBEC) is a promising cooling technique that can find applications in future hadron and electron-ion colliders to counteract intrabeam scattering that limits the maximum achievable luminosity of the collider. To minimize the cooling time, one would use amplification cascades consisting of a drift section followed by a magnetic chicane. In this paper, we first derive and optimize the gain factor in an amplification section for a simplified one-dimensional model of the beam. We then deduce the cooling rate of a system with one and two amplification cascades. We also analyze the noise effects that counteract the cooling process through the energy diffusion in the hadron beam. Our analytical formulas are confirmed by numerical simulations for a set of model parameters.Comment: arXiv admin note: text overlap with arXiv:1806.0278

Wake excited in plasma by an ultrarelativistic pointlike bunch

We study propagation of a relativistic electron bunch through a cold plasma assuming that the transverse and longitudinal dimensions of the bunch are much smaller than the plasma collisionless skin depth. Treating the bunch as a point charge and assuming that its charge is small, we derive a simplified system of equations for the plasma electrons and show that, through a simple rescaling of variables, the bunch charge can be eliminated from the equations. The equations demonstrate an ion cavity formed behind the driver. They are solved numerically and the scaling of the cavity parameters with the driver charge is obtained. A numerical solution for the case of a positively charged driver is also found.Department of Energy DE-AC03-76SF00515U.S. Department of Energy DEFG02-04ER54742 DE-SC0007889 DE-SC0010622Air Force Office of Scientific Research (AFOSR) FA9550-14-1-0045Physic

Calculation of wakefields in 2D rectangular structures

We consider the calculation of electromagnetic fields generated by an electron bunch passing through a vacuum chamber structure that, in general, consists of an entry pipe, followed by some kind of transition or cavity, and ending in an exit pipe. We limit our study to structures having rectangular cross-section, where the height can vary as function of longitudinal coordinate but the width and side walls remain fixed. For such structures, we derive a Fourier representation of the wake potentials through one-dimensional functions. A new numerical approach for calculating the wakes in such structures is proposed and implemented in the computer code ECHO(2D). The computation resource requirements for this approach are moderate and comparable to those for finding the wakes in 2D rotationally symmetric structures. Numerical examples obtained with the new numerical code are presented.Comment: 31 pages, 10 figure