Beam parameters

Basic definitions

Parameter	Description
m0_part	Optional, default: proton mass. [kg] Mass of the beam particles.
q_part	Optional, default: proton charge. [C] Charge of the beam particles.
energy_eV	[eV] Total energy of the beam particles.
Dp_p	Optional, default 0. RMS momentum spread of the beam. Not used if the transverse beam size is given directly through sigmax and sigmay.
nemittx, nemitty	[m] Normalized transverse emittances of the beam. Not used if the transverse beam size is given directly through sigmax and sigmay.
x_beam_pos, y_beam_pos	Optional, default 0. [m] Transverse position of the beam in the chamber.
sigmax, sigmay	Optional, default -1. [m] Transverse RMS beam size. If set to -1, the beam size is calculated from the energy, normalized emittance, dispersion, and momentum spread.

Transverse electric field of the beam

Parameter	Description
beam_field_file	Source of the transverse electric field map of the beam: Name of a .mat file containing the field map. 'computeFD' (or -1): computed with the built-in finite-difference (FD) Poisson solver. 'computeBE': computed with the Bassetti–Erskine formula plus image terms for the elliptical boundary. Only available for elliptical chambers. 'compute_FDSW_multigrid': computed with the built-in FD Poisson solver on nested grids.
save_beam_field_file_as	Optional, default: the field map is not saved. Name of the file in which the field map is saved.

Finite-difference solver ('computeFD')

Parameter	Description
Dh_beam_field	[m] Grid size of the FD solver and of the saved field map.

Bassetti–Erskine ('computeBE')

Parameter	Description
Nx, Ny	Number of points of the field map in each plane.
nimag	Number of image terms.

Multigrid solver ('compute_FDSW_multigrid')

Parameter	Description
Dh_beam_field	[m] Grid size of the FD solver and of the saved field map.
f_telescope_beam	Magnification factor between successive grids. Must satisfy \(0 < f < 1\).
target_grid_beam	Target grid, given as a dictionary with the keys 'x_min_target', 'x_max_target', 'y_min_target', 'y_max_target', and 'Dh_target'.
N_nodes_discard_beam	Number of nodes at the edge of each internal grid that are discarded when interpolating the field (towards the coarser grid).
N_min_Dh_main_beam	Minimum size of the first internal grid, in units of the main grid’s \(\Delta h\).

Longitudinal beam profile

Parameter	Description
b_spac	[s] Bunch spacing. Used to build the profile of a bunched beam. It is also the interval at which the MP set is cleaned and regenerated and at which data is saved.
fact_beam	Scaling factor applied to the beam profile.
coast_dens	Optional, default 0. [particles/m] Coasting beam density added to the beam profile.
flag_bunched_beam	Set to 1 to generate the beam profile from a filling pattern, or to 0 to load it from a file.

Profile from a filling pattern (flag_bunched_beam = 1)

Parameter	Description
sigmaz	[m] RMS bunch length.
t_offs	[s] Time offset of the longitudinal profile. With t_offs = 0, only half of the first bunch is simulated.
filling_pattern_file	Name of a file with the intensities of the bunches, with zeros for empty slots. The pattern can also be given directly as a Python list, e.g. filling_pattern_file = 4*(72*[1.]+8*[0.]).

Profile from a file (flag_bunched_beam = 0)

Parameter	Description
beam_long_prof_file	Name of a .mat file containing the longitudinal beam profile. This file also sets the simulation time step.