Chapter 10
Conclusions and Outlook
Abstract Some overarching conclusions on the current status and the suggestions
for the directions of further development in the edge plasma physics are presented.
Over the whole book, we were emphasizing the complexity and multifaceted nature
of the processes and phenomena in the edge plasma. To unravel the physics of these
processes and phenomena one needs to involve: (i) Classical and anomalous (often
highly intermittent) transport of multispecies plasma including impurities that are
either released due to erosion of the plasma-facing components or introduced into
the edge plasma deliberately to radiate the high power coming from the core (see
Chaps. 6 and 7); (ii) Different issues of atomic physics, including ionization,
recombination and radiation processes involving different species, which often
occur in optically opaque media (see Chap. 2); (iii) Sheath physics and plasma
interactions with the materials of the plasma-facing components, including material
erosion and deposition, saturation with hydrogenic species and impurities, which can
result in modification of the surface morphology and material properties, as well as
an impact of the eroded material, including dust particles, on edge plasma performance (see Chaps. 3, 4 and 5).
All these processes have strongly nonlinear behavior and in many cases exhibit
strong synergistic effects. Therefore, it is very difficult to build simplified analytic or
semi-analytic models that can properly describe the edge plasma phenomena. In
most cases, the outcome of such models needs to be verified with more sophisticated
numerical simulations (e.g. see Chap. 9).
However, because of the complexity of the edge plasma and a large span of
spatiotemporal scales which needs to be covered, the numerical codes are capable of
treating only some “patches” of the necessary spatiotemporal domain. In addition,
they often do not work smoothly even though some significant compromises in the
physics embedded in these codes are usually made. For example, edge plasma
turbulence and edge plasma transport are usually described with different models
and even though the relative turbulent fluctuations of the edge plasma parameters in
many cases exceed 100%, edge plasma transport is described with “laminar” models
where the impact of these fluctuations is ignored (see Chap. 8). Also, most of the
codes (e.g. the edge plasma transport codes such as SOLPS) are based on a
© 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_10
259
Conclusions and Outlook
Abstract Some overarching conclusions on the current status and the suggestions
for the directions of further development in the edge plasma physics are presented.
Over the whole book, we were emphasizing the complexity and multifaceted nature
of the processes and phenomena in the edge plasma. To unravel the physics of these
processes and phenomena one needs to involve: (i) Classical and anomalous (often
highly intermittent) transport of multispecies plasma including impurities that are
either released due to erosion of the plasma-facing components or introduced into
the edge plasma deliberately to radiate the high power coming from the core (see
Chaps. 6 and 7); (ii) Different issues of atomic physics, including ionization,
recombination and radiation processes involving different species, which often
occur in optically opaque media (see Chap. 2); (iii) Sheath physics and plasma
interactions with the materials of the plasma-facing components, including material
erosion and deposition, saturation with hydrogenic species and impurities, which can
result in modification of the surface morphology and material properties, as well as
an impact of the eroded material, including dust particles, on edge plasma performance (see Chaps. 3, 4 and 5).
All these processes have strongly nonlinear behavior and in many cases exhibit
strong synergistic effects. Therefore, it is very difficult to build simplified analytic or
semi-analytic models that can properly describe the edge plasma phenomena. In
most cases, the outcome of such models needs to be verified with more sophisticated
numerical simulations (e.g. see Chap. 9).
However, because of the complexity of the edge plasma and a large span of
spatiotemporal scales which needs to be covered, the numerical codes are capable of
treating only some “patches” of the necessary spatiotemporal domain. In addition,
they often do not work smoothly even though some significant compromises in the
physics embedded in these codes are usually made. For example, edge plasma
turbulence and edge plasma transport are usually described with different models
and even though the relative turbulent fluctuations of the edge plasma parameters in
many cases exceed 100%, edge plasma transport is described with “laminar” models
where the impact of these fluctuations is ignored (see Chap. 8). Also, most of the
codes (e.g. the edge plasma transport codes such as SOLPS) are based on a
© 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_10
259