Chapter 5
Dust in Fusion Plasmas
Abstract Dust is ubiquitous in magnetic fusion devices. It comes either from
plasma-induced erosion of the plasma-facing components or, in some cases, dust
(powder, aerosol) is deliberately injected into edge plasma for some diagnostic or
control purposes. The key processes controlling dust dynamics in the edge plasma
differ significantly from those important in “thin”, low-temperature plasma in the
so-called “dusty plasma” experiments. The main features of dust dynamics in fusion
plasmas, including charging, forces, and ablation processes, are considered in this
chapter.
The fact that dust is present in the plasma of magnetic fusion devices is known for a
long time (e.g. [1–3]). Already Ohkawa [1] had argued that dust particles can be an
important source of impurity in fusion plasmas and can significantly degrade the
performance of fusion plasmas. Later, experimental data confirmed that in some
cases, the appearance of dust particles in fusion plasmas can even result in termination of the plasma discharge (e.g. see Fig. 5.1 and Refs [4, 5]).
The interest to the study of dust-related phenomena in fusion devices was boosted
by the ITER project (see Refs. [7–9]). The main initial concern of the ITER staff was
related to safety issues associated with the chemical activity, tritium retention and
radioactivity of the dust [10] and the dust impact on the in-vessel plasma-facing
diagnostics (e.g. mirrors) [11].
As of today, large amount of experimental data available on (i) in situ dust
observations with Thompson scattering diagnostics and fast cameras, which give
information on the dust size distribution and the dynamics of dust motion (see
Fig. 5.2) through the plasma in fusion devices and (ii) post mortem analysis of the
shape (see Fig. 5.3) and material composition of the dust particles collected in fusion
devices (e.g. see [7, 12–18] and the references therein).
In this chapter, we will consider basic processes involving a dust grain immersed
into fusion plasma, which include grain charging, the forces acting on the grain and
the grain dynamics. We review main dust-related experimental observations related
to the dust parameters, constituency, and dynamics in fusion plasma, dust mobilization from the surfaces of the plasma-facing components, and compare some
experimental data with the results of numerical simulations.
© 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_5
89
Dust in Fusion Plasmas
Abstract Dust is ubiquitous in magnetic fusion devices. It comes either from
plasma-induced erosion of the plasma-facing components or, in some cases, dust
(powder, aerosol) is deliberately injected into edge plasma for some diagnostic or
control purposes. The key processes controlling dust dynamics in the edge plasma
differ significantly from those important in “thin”, low-temperature plasma in the
so-called “dusty plasma” experiments. The main features of dust dynamics in fusion
plasmas, including charging, forces, and ablation processes, are considered in this
chapter.
The fact that dust is present in the plasma of magnetic fusion devices is known for a
long time (e.g. [1–3]). Already Ohkawa [1] had argued that dust particles can be an
important source of impurity in fusion plasmas and can significantly degrade the
performance of fusion plasmas. Later, experimental data confirmed that in some
cases, the appearance of dust particles in fusion plasmas can even result in termination of the plasma discharge (e.g. see Fig. 5.1 and Refs [4, 5]).
The interest to the study of dust-related phenomena in fusion devices was boosted
by the ITER project (see Refs. [7–9]). The main initial concern of the ITER staff was
related to safety issues associated with the chemical activity, tritium retention and
radioactivity of the dust [10] and the dust impact on the in-vessel plasma-facing
diagnostics (e.g. mirrors) [11].
As of today, large amount of experimental data available on (i) in situ dust
observations with Thompson scattering diagnostics and fast cameras, which give
information on the dust size distribution and the dynamics of dust motion (see
Fig. 5.2) through the plasma in fusion devices and (ii) post mortem analysis of the
shape (see Fig. 5.3) and material composition of the dust particles collected in fusion
devices (e.g. see [7, 12–18] and the references therein).
In this chapter, we will consider basic processes involving a dust grain immersed
into fusion plasma, which include grain charging, the forces acting on the grain and
the grain dynamics. We review main dust-related experimental observations related
to the dust parameters, constituency, and dynamics in fusion plasma, dust mobilization from the surfaces of the plasma-facing components, and compare some
experimental data with the results of numerical simulations.
© 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_5
89