According to [80], the “radiation potential” for carbon is about 3 keV at T e ~ 20
eV and falls to ~1 keV at T e ~ 60 eV, showing the trend consistent with Fig. 2.15.
Comparing E
imp
ion ∼ few keV and E
H
ion ∼ 30 eV, we can conclude that impurity starts
to dominate the energy loss from edge plasma when the impurity fraction in the total
flux of neutrals into the plasma from the PFCs exceeds ~1%.
Equation (2.31) can be extended by incorporation of charge-exchange between
the impurity ion and hydrogen atom A
z+1 + H ! A
Z
(n) + H
+ (e.g. see [82]), which
introduces in the function e
L imp one more free parameter, the ratio [H]/n e . This effect
could also increase the impurity radiation loss at high electron temperatures
[20, 82]. However, neutral hydrogen is not abundant where the temperature is high.
2.5 Conclusions
In conclusion to this chapter, it would be fair to say that our knowledge of atomic
processes in the edge plasma is reasonable with respect to both understanding of the
main physical processes and completeness of the data needed to model and diagnose
the most critical processes in the edge plasma of fusion devices. It is not surprising
because our studies in this area are based on the century-old effort of a few
generations of scientists. Nonetheless, some additional data would be needed for
the case where the transport processes in edge plasma should be described kinetically. However, incorporation of plasma kinetic processes and radiation transport
effects into the edge plasma modeling tools is beyond current computer capabilities.
We notice also that the addition of the radiation-induced transitions between different quantum states (e.g. for hydrogen atoms) for opaque regimes, relevant for
detached divertor plasmas in fusion reactors such as ITER, makes the simulation
of the edge plasma very “expensive” computationally. Therefore, there are only a
few cases where such effects were taken into accounted.
References
1. Y.P. Raizer, Gas Discharge Physics (Springer, Berlin, 1991)
2. M.A. Lieberman, A.J. Lichtenberg, Principles of Plasma Discharges and Material Processing
(Wiley, New York, 2005)
3. B.M. Smirnov, Physics of Ionized Gases (Wiley, New York, 2007)
4. L.D. Landau, L.M. Lifshitz, Quantum mechanics (non-relativistic theory), in Course of Theoretical Physics, vol. 3, 3rd edn., (Elsevier Ltd, Oxford, 2005)
5. Y.B. Zeldovich, G.I. Barenblatt, V.B. Librovich, G.M. Makhviladze, The Mathematical Theory
of Combustion and Explosions (Kluiver Academic Publisher Group, Dordrecht, 1985)
6. F.A. Williams, Combustion Theory, 2nd edn. (The Benjamin/Cummings Publishing Company,
Inc, Menlo Park, 1985)
7. D.R. Inglis, E. Teller, Ionic depression of series limits in one-electron spectra. Astrophys. J. 90,
439–442 (1939)
References
43
eV and falls to ~1 keV at T e ~ 60 eV, showing the trend consistent with Fig. 2.15.
Comparing E
imp
ion ∼ few keV and E
H
ion ∼ 30 eV, we can conclude that impurity starts
to dominate the energy loss from edge plasma when the impurity fraction in the total
flux of neutrals into the plasma from the PFCs exceeds ~1%.
Equation (2.31) can be extended by incorporation of charge-exchange between
the impurity ion and hydrogen atom A
z+1 + H ! A
Z
(n) + H
+ (e.g. see [82]), which
introduces in the function e
L imp one more free parameter, the ratio [H]/n e . This effect
could also increase the impurity radiation loss at high electron temperatures
[20, 82]. However, neutral hydrogen is not abundant where the temperature is high.
2.5 Conclusions
In conclusion to this chapter, it would be fair to say that our knowledge of atomic
processes in the edge plasma is reasonable with respect to both understanding of the
main physical processes and completeness of the data needed to model and diagnose
the most critical processes in the edge plasma of fusion devices. It is not surprising
because our studies in this area are based on the century-old effort of a few
generations of scientists. Nonetheless, some additional data would be needed for
the case where the transport processes in edge plasma should be described kinetically. However, incorporation of plasma kinetic processes and radiation transport
effects into the edge plasma modeling tools is beyond current computer capabilities.
We notice also that the addition of the radiation-induced transitions between different quantum states (e.g. for hydrogen atoms) for opaque regimes, relevant for
detached divertor plasmas in fusion reactors such as ITER, makes the simulation
of the edge plasma very “expensive” computationally. Therefore, there are only a
few cases where such effects were taken into accounted.
References
1. Y.P. Raizer, Gas Discharge Physics (Springer, Berlin, 1991)
2. M.A. Lieberman, A.J. Lichtenberg, Principles of Plasma Discharges and Material Processing
(Wiley, New York, 2005)
3. B.M. Smirnov, Physics of Ionized Gases (Wiley, New York, 2007)
4. L.D. Landau, L.M. Lifshitz, Quantum mechanics (non-relativistic theory), in Course of Theoretical Physics, vol. 3, 3rd edn., (Elsevier Ltd, Oxford, 2005)
5. Y.B. Zeldovich, G.I. Barenblatt, V.B. Librovich, G.M. Makhviladze, The Mathematical Theory
of Combustion and Explosions (Kluiver Academic Publisher Group, Dordrecht, 1985)
6. F.A. Williams, Combustion Theory, 2nd edn. (The Benjamin/Cummings Publishing Company,
Inc, Menlo Park, 1985)
7. D.R. Inglis, E. Teller, Ionic depression of series limits in one-electron spectra. Astrophys. J. 90,
439–442 (1939)
References
43