BEAM Command

All MAD commands working on a beam require the setting of various quantities related to this beam. These are entered by a BEAM command:

label:BEAM,PARTICLE=name,MASS=real,CHARGE=real,
      ENERGY=real,PC=real,GAMMA=real,BCURRENT=real,
      EX=real,EXN=real,EY=real,EYN=real,ET=real,
      KBUNCH=integer,NPART=real,BUNCHED=logical,
      RADIATE=logical,DAMP=logical,QUANTUM=logical;

The label is opional, it defaults to UNNAMED_BEAM. The particle mass and charge are defined by:

PARTICLE The name of particles in the machine. MAD knows the mass and the charge for the following particles:

POSITRON The particles are positrons (MASS=$m\_e$, CHARGE=1),

ELECTRON The particles are electrons (MASS=$m\_e$, CHARGE=-1),

PROTON The particles are protons (default, MASS=$m\_p$, CHARGE=1),

ANTIPROTON The particles are anti-protons (MASS=$m\_p$, CHARGE=-1).

For other particle names one may enter:

MASS The particle mass in GeV.

CHARGE The particle charge expressed in elementary charges.

By default the particle momentum is P0. A different value can be defined by one of the following:

ENERGY The total energy per particle in GeV. If given, it must be greater then the particle mass.

PC The momentum per particle in GeV/c. If given, it must be greater than zero.

GAMMA The ratio between total energy and rest energy of the particles $\gamma = E / m_0$. If given, it must be greater than one. If the mass is changed a new value for the energy should be entered. Otherwise the energy remains unchanged, and the momentum and $\gamma$ are recalculated.

The emittances are defined by:

EX The horizontal emittance $E_x=\sigma_x^2/\beta_x$ (default: 1 m).

EY The vertical emittance $E_y=\sigma_y^2/\beta_y$ (default: 1 m).

ET The longitudinal emittance $E_t=\sigma_e/(p_0c) \cdot c\sigma_t$ (default: 1 m). The emittances can be replaced by the normalised emittances and the energy spread:

EXN The normalised horizontal emittance [m]: $E_{xn}=4\beta\gamma E_x$ (ignored if $E_x$ is given).

EYN The normalised vertical emittance [m]: $E_{yn}=4\beta \gamma E_y$ (ignored if $E_y$ is given).

SIGT The bunch length $c\sigma_t$ [m].

SIGE The relative energy spread $\sigma_e/p_0 c$ [1].

For the time being, only the particle definition (PARTICLE,MASS,CHARGE,PC,ENERGY,GAMMA) is used. The other parameters will be implemented as needed when new commands become available.