Effective beam emission/population coefficients
The data sets are collections of beam emission coefficients, given the mnemonic BME. The processes and influences on the emission are the same as those responsible for beam stopping and the emission coefficients are obtained as a product of the same collisional–radiative models as the beam stopping coefficients. ADF22 is a derived data format and the data sets are structured in a similar manner to those of ADF21. Thus data sets are for a single impurity (assumed fully ionised with their associated free electrons under charge conservation) and for a specific spectrum line. A reference parameter set is specified and coefficient data are tabulated as an array in beam energy and density and as a vector in temperature, centred on the reference values. Emission by a mixed impurity plasma is assembled as a linear combination of pure species emission coefficients. It is recommended that the detailed prescription and use be examined with care. Beam emission is related to the electron density in ADF22 as for ADF21. ADF22 spans both hydrogen and helium with sub-directories for the different beam species and for different reference conditions (fast and and slow beams). For hydrogen beams, data are only given for H$_\alpha$. For helium, there are additional sub-directories for a number of spectrum lines. The helium is treated as a metastable-resolved atom (ground and two metastables) as in ADF21 and so there are beam emission coefficient data sets relating to each of the metastables as a driver population. See Anderson et al (2000) for more detail on beam emission.