13 Beam Command

The BEAM command defines the particle species, reference energy or momentum, and global beam properties used by tracking and diagnostics.

label: BEAM, PARTICLE=name, MASS=real, CHARGE=real,
      ENERGY=real, PC=real, GAMMA=real, BCURRENT=real,
      NPART=real, BFREQ=real;

The label is optional and defaults to UNNAMED_BEAM.

13.1 Particle Definition

PARTICLE selects one of the predefined species such as ELECTRON, POSITRON, MUON, PROTON, DEUTERON, HMINUS, H2P, ALPHA, CARBON, XENON, or URANIUM.

For custom species, the user can provide:

MASS in GeV
CHARGE in elementary-charge units

13.2 Beam Energy

There are three standard energy attributes, with the usual priority:

GAMMA
ENERGY
PC

13.3 Other Attributes

The other important beam attributes are:

BFREQ: bunch frequency in MHz.
BCURRENT: bunch current in A.
NPART: number of macro particles used in the simulation.
NSLICE: number of slices per bunch.
MOMENTUMTOLERANCE: tolerance used when checking consistency between the distribution and the reference momentum.