sputtering, it is still difficult to make quantitative predictions of both reflection and
sputtering for the case where the constituency of the first atomic layers of the wall
material is evolving in time due to the plasma-material interactions. The situation
becomes even worse if we need to make an assessment of helium and hydrogen
transport in the material lattice. It seems that we understand the basics of the helium
trapping mechanism at relatively low target temperatures, but we are yet unable to
provide reliable models of the growth of fuzzy structures when the temperature goes
up. For hydrogen transport and retention in tungsten, few primary mechanisms of
hydrogen trapping were identified (e.g. SAV, dislocations). But still, no definite
conclusion has been reached among the scientific community. In addition, there are
some indications of a possible nonlinear, hydrogen-induced generation of the traps
but there is no quantitative, predictive theoretical model that could be challenged by
the experimental data yet. Interestingly, the experimental data on hydrogen retention
in tungsten, for the conditions excluding such unwanted and complex effects as
blistering, suggest that for large hydrogen fluence, Φ H , the amount of trapped
hydrogen is simply proportional to
ffiffiffiffiffiffi ffi
Φ H
p
[65].
References
1. D. Stork, S.J. Zinkle, Introduction to the special issue on the technical status of materials for a
fusion reactor. Nucl. Fusion 57, 092001 (2017)
2. J. Roth, E. Tsitrone, A. Loarte, T. Loarer, G. Counsell, R. Neu, V. Philipps, S. Brezinsek,
M. Lehnen, P. Coad, C. Grisolia, K. Schmid, K. Krieger, A. Kallenbach, B. Lipschultz,
R. Doerner, R. Causey, V. Alimov, W. Shu, O. Ogorodnikova, A. Kirschner, G. Federici,
A. Kukushkin, EFDA PWI Task Force, ITER PWI Team, Fusion for Energy, ITPA SOL/DIV,
Recent analysis of key plasma wall interactions issues for ITER. J. Nucl. Mater. 390–391, 1–9
(2009)
3. S. Brezinsek, T. Loarer, V. Philipps, H.G. Esser, S. Grűnhagen, R. Smith, R. Felton, J. Banks,
P. Belo, A. Boboc, J. Bucalossi, M. Clever, J.W. Coenen, I. Coffey, S. Devaux, D. Douai,
M. Freisinger, D. Frigione, M. Groth, A. Huber, J. Hobirk, S. Jachmich, S. Knipe, K. Krieger,
U. Kruezi, S. Marsen, G.F. Matthews, A.G. Meigs, F. Nave, I. Nunes, R. Neu, J. Roth,
M.F. Stamp, S. Vartanian, U. Samm, JET EFDA contributors, Fuel retention studies with
the ITER-Like Wall in JET. Nucl. Fusion 53, 083023 (2013)
4. P. Roubin, B. Pégourié, R. Smirnov, C. Martin, M. Richou, Y. Marandet, C. Pardanaud,
C. Brosset, J. Gunn, Analysis of carbon deposited layer growth processes in Tore
supra. J. Nucl. Mater. 390–391, 49–52 (2009)
5. S. Kajita, W. Sakaguchi, N. Ohno, N. Yoshida, T. Saeki, Formation process of tungsten
nanostructure by the exposure to helium plasma under fusion relevant plasma conditions.
Nucl. Fusion 49, 095005 (2009)
6. T. Tanabe, Review of hydrogen retention in tungsten. Phys. Scr. T159, 014044 (2014)
7. P. Hohenberg, W. Kohn, Inhomogeneous electron gas. Phys. Rev. 136, B864–B871 (1964)
8. http://www.quantum-espresso.org/
9. G. Kresse, J. Hafner, Ab initio molecular dynamics for liquid metals. Phys. Rev. B 47,
558–561 (1993)
10. http://lammps.sandia.gov/
11. W. Möller, W. Eckstein, J.P.Biersack, Tridyn-binary collision simulation of atomic collisions
and dynamic composition changes in solids. Comput. Phys. Commun. 51, 355–368 (1988)
66
3 Plasma-Material Interactions in Magnetic Fusion Devices
sputtering for the case where the constituency of the first atomic layers of the wall
material is evolving in time due to the plasma-material interactions. The situation
becomes even worse if we need to make an assessment of helium and hydrogen
transport in the material lattice. It seems that we understand the basics of the helium
trapping mechanism at relatively low target temperatures, but we are yet unable to
provide reliable models of the growth of fuzzy structures when the temperature goes
up. For hydrogen transport and retention in tungsten, few primary mechanisms of
hydrogen trapping were identified (e.g. SAV, dislocations). But still, no definite
conclusion has been reached among the scientific community. In addition, there are
some indications of a possible nonlinear, hydrogen-induced generation of the traps
but there is no quantitative, predictive theoretical model that could be challenged by
the experimental data yet. Interestingly, the experimental data on hydrogen retention
in tungsten, for the conditions excluding such unwanted and complex effects as
blistering, suggest that for large hydrogen fluence, Φ H , the amount of trapped
hydrogen is simply proportional to
ffiffiffiffiffiffi ffi
Φ H
p
[65].
References
1. D. Stork, S.J. Zinkle, Introduction to the special issue on the technical status of materials for a
fusion reactor. Nucl. Fusion 57, 092001 (2017)
2. J. Roth, E. Tsitrone, A. Loarte, T. Loarer, G. Counsell, R. Neu, V. Philipps, S. Brezinsek,
M. Lehnen, P. Coad, C. Grisolia, K. Schmid, K. Krieger, A. Kallenbach, B. Lipschultz,
R. Doerner, R. Causey, V. Alimov, W. Shu, O. Ogorodnikova, A. Kirschner, G. Federici,
A. Kukushkin, EFDA PWI Task Force, ITER PWI Team, Fusion for Energy, ITPA SOL/DIV,
Recent analysis of key plasma wall interactions issues for ITER. J. Nucl. Mater. 390–391, 1–9
(2009)
3. S. Brezinsek, T. Loarer, V. Philipps, H.G. Esser, S. Grűnhagen, R. Smith, R. Felton, J. Banks,
P. Belo, A. Boboc, J. Bucalossi, M. Clever, J.W. Coenen, I. Coffey, S. Devaux, D. Douai,
M. Freisinger, D. Frigione, M. Groth, A. Huber, J. Hobirk, S. Jachmich, S. Knipe, K. Krieger,
U. Kruezi, S. Marsen, G.F. Matthews, A.G. Meigs, F. Nave, I. Nunes, R. Neu, J. Roth,
M.F. Stamp, S. Vartanian, U. Samm, JET EFDA contributors, Fuel retention studies with
the ITER-Like Wall in JET. Nucl. Fusion 53, 083023 (2013)
4. P. Roubin, B. Pégourié, R. Smirnov, C. Martin, M. Richou, Y. Marandet, C. Pardanaud,
C. Brosset, J. Gunn, Analysis of carbon deposited layer growth processes in Tore
supra. J. Nucl. Mater. 390–391, 49–52 (2009)
5. S. Kajita, W. Sakaguchi, N. Ohno, N. Yoshida, T. Saeki, Formation process of tungsten
nanostructure by the exposure to helium plasma under fusion relevant plasma conditions.
Nucl. Fusion 49, 095005 (2009)
6. T. Tanabe, Review of hydrogen retention in tungsten. Phys. Scr. T159, 014044 (2014)
7. P. Hohenberg, W. Kohn, Inhomogeneous electron gas. Phys. Rev. 136, B864–B871 (1964)
8. http://www.quantum-espresso.org/
9. G. Kresse, J. Hafner, Ab initio molecular dynamics for liquid metals. Phys. Rev. B 47,
558–561 (1993)
10. http://lammps.sandia.gov/
11. W. Möller, W. Eckstein, J.P.Biersack, Tridyn-binary collision simulation of atomic collisions
and dynamic composition changes in solids. Comput. Phys. Commun. 51, 355–368 (1988)
66
3 Plasma-Material Interactions in Magnetic Fusion Devices