Zeff in TRANSP can be defined from the plasma composition or from the plasma resistivity. The latter is available only when the poloidal field diffusion is evolved.
Plasma composition Zeff
With this option TRANP uses the quasi-neutrality condition to infer the impurity and hydrogenic species concentration from electron density and Zeff. 
The plasma composition Zeff can be obtained from namelist settings and/or from input UFILES and can be rescaled according to Visible Bremsstrahlung data, if provided.
Constant value
Zeff can be set constant in time and space, by defining the desired value in the namelist variable XZEFFI. This is also the default if no other option is selected for how to calculate Zeff. Note that XZEFFI is updatable in time from the namelist.
Flat profile
A flat profile is assumed everytime a Zeff(t) is provided via a PREZEF/EXTZEF UFILE. This case is similar to the previous with the difference that Zeff in time is not defined in the namelist, but provided from experiments. This option is compatible with using data from Visible Bremsstrahlung.Analytic profile
To avoid using a flat profile when reading Zeff from PREZEF/EXTZEF, the value of Zeff at the edge can be provided (see below, NLZEFA option). In this case, TRANSP will use the input Zeff from UFILE as the central value and construct an analytic profile according to the form:
The coefficients a1 and a2 control the plasma shape and are set in the namelist variables XZFA1 and XZFA2 respectively. Default values are XZFA1=2.0 and XZFA2=0.0. The radial coordinate x represents the flux surface label, x=r/a.
XZFA1 is contrained to be positive. If XZFA1 > 1.0 then the following conditions are satisfied:
If reading the Visible Bremsstrahlung data, then the value of Zeff(0) is adjusted between 1.0 and the atomic number Z to match the VB input data.
Profile from experimental data
The Zeff profile can be given directly as in input via PREZF2/EXTZF2 UFILEs (see option NLZFI2 below). If the VB data are also provided, the impurity profiles will be rescaled according to these data.
Plasma resistivity Zeff
Namelist options
- NLZEFM
- Set this TRUE to set Zeff from the plasma resistivity. A multiplicative factor can be used to rescale the resistivity, as Zeff=CZEFFMxZeff,res. The default value is CZEFFM=1.0. Then the impurities will be rescaled according to Zeff.
- NLZFIN
- Set this to TRUE to read 1D UFILE PREZEF/EXTZEF of Zeff(t).
- NLZFI2
- Set this to TRUE to read 2D UFILES PREZF2/EXTZF2 of profiles of Zeff(x,t). Need to define also the symmetrization profile option with NSYZF2 and the radial coordinate with NRIZF2.
- NLZFXI
- Set this to TRUE to read 2D UFILES PRENIM/EXTNIM of profiles of single impurity, nZ(x,t). Need to define also the symmetrization profile option with NSYNIM and the radial coordinate with NRINIM. This is compatible with the input of Visible Bremsstrahlung data (PREVSB/EXTVSB).
- NLZSIM
- Set this to TRUE to use multiple impurity data, either PRESIM/EXTSIM input UFILES, or DENSIM/DENSIMA input or both. If PRESIM/EXTSIM UFILES are provided, need to define also symmetrization option with NSYSIM and radial coordinate with NRISIM, for each impurity. This is also compatible with input Visible Bremsstrahlung data.
- NLVISB
- Set this TRUE to read 1D UFILES PREVSB/EXTVSB of Visible Bremsstrahlung chordal data.
- In addition, set NLZVBR=.T. to use the VB data to rescale the impurity density, otherwise the data are only read by TRANSP and can be used for output comparison.
- NLVISB can be used in combination with NLZVBR and NLZEFA. In this case the edge Zeff is taken from the UFILE or from XZEFFAI and the central value Zeff(0) is adjusted to match the VB data.
- NLVISB can be used in combination with NLZVBR and NLZFXI. In this case the impurity density profile is rescaled to match the chordal VB data.
- NLVB2
- Set this to TRUE to read 2D UFILEs PREVB2/EXTVB2 of emissivity (processed via Abel inversion). It also needs definition of profile symmetrization with NSYVB2 and definition of the radial coordinate with NRIVB2.
- In addition, set NLZVB2=.T. to use the VB2 profiles to rescale the impurity density, otherwise the data are only read by TRANSP and can be used for output comparison.
- NLZEFA
- Set TRUE to use data for the edge Zeff. These can be given to TRANSP either as an 1D UFILE PREZFA/EXTZFA or in the namelist variable XZEFFA1 (variable updatable in time). The option NLZEFA=.T. must be used with NLZFIN=.T. or with NLVISB and NLZVBR.
Additional ion sources
Beam ions and minority species are included in the calculation of Zeff, with some exceptions.
- ABEAM
- to specify beam ions when only one beam species is present, which is hydrogenic.
- XZBEAMA, ABEAMA
- to specify beam ions when more than one beam species is present or when helium beams are present.
- XZMINI, AMINI
- to specify ICRF minority species
- APEL
- to specify the pellet atomic mass