Chapter 2
Atomic Physics Relevant to Fusion Plasmas
Abstract Atomic physics processes involving electrons, ions and neutrals of
hydrogenic species and impurities are playing a vital role in virtually all macroscopic
edge plasma phenomena. In this chapter a brief overview of the essentials of atomic
physics relevant to the edge plasma processes is given.
As demonstrated in Chap. 1, both the atomic physics and the interactions of plasma
with the materials of the PFCs (in particular, the first wall of the vacuum chamber
and divertor targets) play very important role in virtually all edge plasma phenomena
including plasma recycling, energy dissipation, divertor detachment, erosion of the
PFCs, plasma contamination with impurities, etc. In this chapter, we will focus on
the atomic physics issues relevant to fusion plasmas.
Although atomic physics processes at the edge of magnetic fusion devices have
some similarity to those in low-temperature gas discharge plasmas (e.g. see [1–3]),
which have been under intense theoretical studies over 100 years, there are also
important differences. First, the fusion plasma consists mostly of hydrogenic species, having some (~10%) helium as well as a potentially controlled (deliberately
injected), relatively small percentage (~1%) of impurity species (e.g. neon, argon,
etc.) for plasma cooling, and some fraction of impurities originated from erosion of
the PFC materials (e.g. lithium, beryllium, tungsten, etc.). Secondly, unlike most of
the gas discharges that feature rather homogeneous, low temperature (~1 eV)
plasmas, the edge plasma parameters in fusion devices are very non-uniform
(e.g. the edge plasma temperature in the discharge can vary from sub-eV to few
100 eV). As a result, atomic processes taking place in edge plasma are very diverse
and ranging from plasma recombination in low-temperature regions to both neutral
hydrogen and impurity ionization at high temperatures (we notice that at temperature ~ keV, neon can be completely stripped off of all electrons). As we will see, both
diversity and inhomogeneity of the edge plasma parameters increase the number of
atomic processes that should be allowed for, which complicates the edge plasma
description.
In this section, we review basic quantum mechanical features of atomic species
relevant for edge plasma studies and discuss the physics behind the CollisionalRadiative Model (CRM) widely used in fusion research for the description of the
© Springer Nature Switzerland AG 2020
S. Krasheninnikov et al., On the Edge of Magnetic Fusion Devices, Springer Series in
Plasma Science and Technology, https://doi.org/10.1007/978-3-030-49594-7_2
13
Atomic Physics Relevant to Fusion Plasmas
Abstract Atomic physics processes involving electrons, ions and neutrals of
hydrogenic species and impurities are playing a vital role in virtually all macroscopic
edge plasma phenomena. In this chapter a brief overview of the essentials of atomic
physics relevant to the edge plasma processes is given.
As demonstrated in Chap. 1, both the atomic physics and the interactions of plasma
with the materials of the PFCs (in particular, the first wall of the vacuum chamber
and divertor targets) play very important role in virtually all edge plasma phenomena
including plasma recycling, energy dissipation, divertor detachment, erosion of the
PFCs, plasma contamination with impurities, etc. In this chapter, we will focus on
the atomic physics issues relevant to fusion plasmas.
Although atomic physics processes at the edge of magnetic fusion devices have
some similarity to those in low-temperature gas discharge plasmas (e.g. see [1–3]),
which have been under intense theoretical studies over 100 years, there are also
important differences. First, the fusion plasma consists mostly of hydrogenic species, having some (~10%) helium as well as a potentially controlled (deliberately
injected), relatively small percentage (~1%) of impurity species (e.g. neon, argon,
etc.) for plasma cooling, and some fraction of impurities originated from erosion of
the PFC materials (e.g. lithium, beryllium, tungsten, etc.). Secondly, unlike most of
the gas discharges that feature rather homogeneous, low temperature (~1 eV)
plasmas, the edge plasma parameters in fusion devices are very non-uniform
(e.g. the edge plasma temperature in the discharge can vary from sub-eV to few
100 eV). As a result, atomic processes taking place in edge plasma are very diverse
and ranging from plasma recombination in low-temperature regions to both neutral
hydrogen and impurity ionization at high temperatures (we notice that at temperature ~ keV, neon can be completely stripped off of all electrons). As we will see, both
diversity and inhomogeneity of the edge plasma parameters increase the number of
atomic processes that should be allowed for, which complicates the edge plasma
description.
In this section, we review basic quantum mechanical features of atomic species
relevant for edge plasma studies and discuss the physics behind the CollisionalRadiative Model (CRM) widely used in fusion research for the description of the
© Springer Nature Switzerland AG 2020
S. Krasheninnikov et al., On the Edge of Magnetic Fusion Devices, Springer Series in
Plasma Science and Technology, https://doi.org/10.1007/978-3-030-49594-7_2
13