Background species
TRANSP can accommodate up to seven thermal ion species which may be isotopes of Hydrogen, Helium or Lithium. Users need ot specify:
- NG
- Initial number of plasma background species
- NGMAX
- Maximum number of background species
- BACKZ(j)
- atomic number of each background species j=1,NGMAX
- APLASM(j)
- atomic weight of each background species, for j=1,NGMAX.
- NOTE: in TRANSP the atomic weight is defined in units of the proton mass: A = m/mp. Hydrogen will have A=1.000. If APLASM is defined in AMU (thus Hydrogen would have A=1.0079), then the input will be normalized to A=1.0079. This correction is made for all ions, i.e. background species, impurities, beam species, fusion products, minority species, pellets. Exception: single impurity model (tokamakium).
- FRAC
- to specify the initial relative fraction of thermal ions. TRANSP will then evolve the ion densities according to particel balance and quasi-neutrality, according to the ion transport model, which is selected with NDEFINE.
IMPORTANT: Fusion products, minority species, beam ions and alpha particles should not be defined as background species. However, if beam ion sources are distinct from background species (i.e. hydrogen beams in deuterium or helium plasmas, or tritium beams in deuterium plasmas) then the maximum number of species must be large enough to accommodate all thermalized species.
For impurity settings, see section on Impurities