Dynamics Of Space-charge Dominated Beams Research Articles

Numerical Simulations of Space Charge Dominated Beam Dynamics in Experimentally Optimized PITZ RF Photogun

Numerical Simulations of Space Charge Dominated Beam Dynamics in Experimentally Optimized PITZ RF Photogun

Experimental validation of collective effects modeling at injector section of X-ray free-electron laser

We consider the collective beam dynamics at the injector section of the European XFEL. The results of the measurements for the longitudinal phase space (LPS) of the electron beam are compared with those obtained from numerical modeling. A new approach is proposed for the analysis of the self-field effects in the LPS measurements. It allows to determine accurately the synchronous RF phase in an accelerating module and to subtract properly the RF curvature imprinted in the LPS. A further incorporation with the simulation made it possible to separate the collective effects originating from different sources and thus to quantify, individually, the impact of these effects on the beam dynamics. This includes the space-charge dominated beam dynamics in the RF gun as well as the collective effects dominated by the wake fields after the gun up to the end of the injector section. A new analytical model is also proposed for the short-range wake function of a finite chain of RF cavities and verified by both numerical analysis and experimental results. It is shown that the physical models used in the simulation of the beam dynamics after the gun allow to reduce the absolute error in the modeling of the correlated energy chirp by order of magnitude in comparison with the case when the collective effects after the gun are neglected.

Self-consistent space charge dominated beam dynamics in a spiral inflector

In this paper, a simplified approach is presented to investigate the dynamics of space charge dominated beam self-consistently in a spiral inflector. We have used a uniform density beam and studied the behavior of beam envelope and emittance growth that results from the coupling between the two transverse planes. It is shown that an inflector with large height and small tilt parameter produces comparatively less emittance growth. We have used axisymmetric and non-axisymmetric input beam and optimized the initial conditions to reduce the emittance growth at the exit of the inflector. Simulation results show that a converging non-axisymmetric beam with equal emittances at the entrance is desirable to reduce the emittance growth at the exit.

Space charge dominated beam dynamics in a spiral inflector for a compact cyclotron

Beam optical properties of a spiral inflector in the presence of space charge effects have been studied for a high-current compact proton cyclotron. The space charge effect has been incorporated in the paraxial ion trajectory calculations considering the beam as a uniform ellipsoidal bunch. The increase in the current in the bunch due to bunching as the beam passes through the inflector has been included in the beam dynamics. The initial conditions of the beam have been optimized to reduce the emittance growth at the exit of the inflector. The four-dimensional transverse acceptance of the spiral inflector as a function of beam current has been estimated. We have also used the infinitesimal transfer matrix technique to estimate the beam envelope and compared the results with those obtained by paraxial ray tracing.

Development of 2D particle-in-cell code to simulate high current, low energy beam in a beam transport system

A code for 2D space-charge dominated beam dynamics study in beam transport lines is developed. The code is used for particle-in-cell (PIC) simulation of z-uniform beam in a channel containing solenoids and drift space. It can also simulate a transport line where quadrupoles are used for focusing the beam. Numerical techniques as well as the results of beam dynamics studies are presented in the paper.

EXPERIMENTAL TESTING OF DYNAMICALLY OPTIMIZED PHOTOELECTRON BEAMS

We discuss the design of and initial results from an experiment in space-charge dominated beam dynamics which explores a new regime of high-brightness electron beam generation at the SPARC (located at INFN-LNF, Frascati) photoinjector. The scheme under study employs the natural tendency in intense electron beams to configure themselves to produce a uniform density, giving a nearly ideal beam from the viewpoint of space charge-induced emittance. The experiments are aimed at testing the marriage of this idea with a related concept, emittance compensation, We show that the existing infrastructure at SPARC is nearly ideal for the proposed tests, and that this new regime of operating photoinjector may be the preferred method of obtaining highest brightness beams with lower energy spread. We discuss the design of the experiment, including developing of a novel time-dependent, aerogel-based imaging system. This system has been installed at SPARC, and first evidence for nearly uniformly filled ellipsoidal charge distributions recorded.

Particle-in-cell code BEAMPATH for beam dynamics simulations in linear accelerators and beamlines

A code library BEAMPATH for 2D and 3D space charge dominated beam dynamics study in linear particle accelerators and beam transport lines is developed. The program is used for particle-in-cell simulation of axial-symmetric, quadrupole-symmetric and z-uniform beams in a channel containing RF gaps, radio-frequency quadrupoles, multipole lenses, solenoids and bending magnets. The programming method includes hierarchical program design using program-independent modules and a flexible combination of modules to provide the most effective version of the structure for every specific case of simulation. Numerical techniques as well as the results of beam dynamics studies are presented.

3D simulation of space-charge—dominated beam dynamics

In this note we analyze the structure of the code TREDI, devoted to the simulation of space-charge-dominated beam dynamics in three spatial dimensions. The integration method, based on the Lienard-Wiechert potential formalism, is quite general and allows the analysis of a wide class of physical problems ranging from Coulomb repulsion in low-energy beams to coherent synchrotron radiation effects in the high-energy regime. This versatility has been exploited in a simulation where the beam dynamics is followed starting from the cathode, through the acceleration/transport system, up to an undulator magnet.