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The technique of microbunched electron cooling (MBEC) is a coherent cooling scheme with possible applications in high-energy hadron and electron-ion machines. In our previous work we analyzed the cooling of the hadron energy spread and transverse emittance using a one-dimensional (1D) technique that tracked the microscopic fluctuations in the hadron and electron beams. However, in order to obtain analytical expressions for our key quantities, we limited ourselves to calculating and optimizing only the initial values of the cooling rates. In this paper, we extend our approach so that it properly addresses the issue of the long-term, dynamic evolution of the hadron beam. In order to do so, it becomes necessary to consider the synchrotron motion of the hadron beam, in conjunction with the effects of diffusion and intrabeam scattering (IBS). With these modifications, our formalism allows us to develop a simple numerical tool that can effectively model the final state of hadron beam after many passages through the MBEC cooler.

The technique of microbunched electron cooling (MBEC) is an attractive coherent cooling scheme with potential applications in future high-energy circular colliders. In our previous work, we analyzed the cooling of the energy spread using a one-dimensional (1D) technique that tracks the dynamics of microscopic fluctuations in the hadron and electron beams. In this paper, we extend this approach so that it covers the transverse emittance cooling as well. In order to do so, it is necessary to consider the betatron motion of the hadron beam and take into account effects of the momentum dispersion in the modulator and kicker regions. We derive relatively simple analytical expressions for the emittance and energy spread cooling times in terms of the various beam and lattice parameters, allowing us to perform fast optimization studies for an MBEC configuration. Verified through comparison with simulation, our theory can also incorporate features such as plasma amplification stages, which are crucial components of a realistic cooling system.

The method of enhanced self-amplified spontaneous emission (eSASE) is one of the strongest candidates for the generation of sub-femtosecond x-ray pulses in a free-electron laser (FEL). The optimization of an eSASE experiment involves many independent parameters, which makes the exploration of the parameter space with thee-dimensional (3D) simulations computationally intensive. Therefore, a robust theoretical analysis of this problem is extremely desirable. We provide a self-consistent, analytical treatment of such a configuration using a one-dimensional (1D), time-dependent FEL model that includes the key effects of electron beam chirp and undulator taper. Verified via comparison with numerical simulation, our formalism is utilized in parameter studies that seek to determine the optimum setup of the FEL.

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 ultrarelativistic drive beam is highly nonlinear. Thus, fast and accurate simulation 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.

In a free-electron laser, a transverse momentum offset (or ``kick'') results in an oscillation of the centroid of the electron beam about the undulator axis. Studying the influence of this effect on the free-electron laser (FEL) interaction is important both from a tolerance point of view and for its potential diagnostic applications. In this paper, we present a self-consistent theoretical analysis of a high-gain FEL driven by such a ``kicked'' beam. In particular, we derive a solution to the three-dimensional, linearized initial value problem of the FEL through an orthogonal expansion technique and also describe a variational method for calculating the average FEL growth rate. Our results are benchmarked with genesis simulations and provide a robust theoretical background for a comparison with previous analytical results.