A beamline to control longitudinal phase space whilst transporting laser wakefield accelerated electrons to an undulator

Laser wakefield accelerators (LWFAs) can produce high-energy electron bunches in short distances. Successfully coupling these sources with undulators has the potential to form an LWFA-driven free-electron laser (FEL), providing high-intensity short-wavelength radiation. Electron bunches produced from LWFAs have a correlated distribution in longitudinal phase space: a chirp. However, both LWFAs and FELs have strict parameter requirements. The bunch chirp created using ideal LWFA parameters may not suit the FEL; for example, a chirp can reduce the high peak current required for free-electron lasing. We, therefore, design a flexible beamline that can accept either positively or negatively chirped LWFA bunches and adjust the chirp during transport to an undulator. We have used the accelerator design program MAD8 to design a beamline in stages, and to track particle bunches. The final beamline design can produce ambidirectional values of longitudinal dispersion (R56): we demonstrate values of + 0.20 mm, 0.00  mm and − 0.22 mm. Positive or negative values of R56 apply a shear forward or backward in the longitudinal phase space of the electron bunch, which provides control of the bunch chirp. This chirp control during the bunch transport gives an additional free parameter and marks a new approach to matching future LWFA-driven FELs

Design of a double dipole electron spectrometer

With the increase of laser power at facilities reaching petawatt-level, there is a need for accurate electron beam diagnostics of the laser wakefield accelerator (LWFA), which are becoming important tools for a wide range of applications including high field physics. Electrons in the range of several 10 0s of GeV are expected at these power levels. Precise diagnostic systems are required to enable applications such as advanced radiation sources. Accurate measurement of the energy spread of electron beams will help pave the way towards LWFA based free-electron lasers and plasma based coherent radiation sources. We propose an innovative double dipole spectrometer suitable for characterizing bunches produced using a petawatt class laser

Vacuum ultraviolet coherent undulator radiation from attosecond electron bunches

Attosecond duration relativistic electron bunches travelling through an undulator can generate brilliant coherent radiation in the visible to vacuum ultraviolet spectral range. We present comprehensive numerical simulations to study the properties of coherent emission for a wide range of electron energies and bunch durations, including space-charge effects. These demonstrate that electron bunches with r.m.s. duration of 50 as, nominal charge of 0.1 pC and energy range of 100–250 MeV produce 109 coherent photons per pulse in the 100–600 nm wavelength range. We show that this can be enhanced substantially by self-compressing negatively chirped 100 pC bunches in the undulator to produce 1014 coherent photons with pulse duration of 0.5–3 fs

The General particle tracer code: design, implementation and application

viii+220hlm.;24c

Progress in 3D Space-charge Calculations in the GPT Code

The mesh-based 3D space-charge routine in the GPT (General Particle Tracer, Pulsar Physics) code scales linearly with the number of particles in terms of CPU time and allows a million particles to be tracked on a normal PC. The crucial ingredient of the routine is a non-equidistant multi-grid Poisson solver to calculate the electrostatic potential in the rest frame of the bunch. The solver has been optimized for very high and very low aspect ratio bunches present in state-of-the-art high-brightness electron accelerators. In this paper, we explore the efficiency and accuracy of the calculations as function of meshing strategy and boundary conditions

TESLA Report 2003-31 Multigrid Algorithms for the Fast Calculation of Space-Charge Effects in Accelerator Design

Numerical prediction of the performance of charged particle accelerators is essential for the design and understanding of these machines. Methods to calculate the self-fields of accelerated particles, the so-called spacecharge forces, become increasingly important as the demand for high-quality bunches increases. We report on our development of a new 3D space-charge routine in the General Particle Tracer (GPT) code. It scales linearly with the number of particles in terms of CPU time, allowing detailed design studies with over a million sample particles on a normal PC. The model is based on a nonequidistant multigrid Poisson solver that has been constructed to solve the electrostatic fields in the rest frame of the bunch on meshes with large aspect ratio. Theoretical and numerical investigations of the behaviour of SOR relaxation and PCG method on non-equidistant grids emphasize the advantages of the multigrid algorithm with adaptive coarsening. Numerical investigations have been performed with a selected range of cylindrically shaped bunches (from very long to very short) spanning a wide range of recent applications. The application to the simulation of the photoinjector at the Eindhoven University of Technology demonstrates the power of the new 3D routine

RF Compression of sub-relativistic space-charge-dominated electron bunches for single-shot femtosecond electron diffraction

Abstract only

Novel electron bunch creation towards ultrafast electron diffraction

Abstract only

3D Space-charge model for GPT simulations of high-brightness electron bunches

For the simulation of high-brightness electron bunches, a new 3D space-charge model is being implemented in the General Particle Tracer (GPT) code. It is based on a non-equidistant multigrid solver, allowing smooth transitions from a high to a low-aspect ratio bunch during a single run. The algorithm scales linearly in CPU time with the number of particles and the insensitivity to aspect ratio ensures that it can be used for a variety of applications. Tracking examples and field comparisons with an analytical model will be shown