52
4 Responses of Plasma-Facing Surface to Power Load Given by Radiation …
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e -
e -
e -
e -
e -
e -
e -
e -
e -
e -
e -
e -
e -
e -
e -
e -
e -
e -
e -
e -
e -
Scattered ion
Electron excitation
dominated area
Interstitial atom
Atomic collision
Vacancy
Incident ion
+ Ionized lattice atom
e - Excited electrons
Interstitial atom
Lattice atom
Vacancy
Fig. 4.3 Schematic drawing for energy loss process of energetic particle injected in a solid
become dominant. Because energy loss by the nuclear collision is much larger than
that of the ionization, the incident ion stops after repeating the nuclear collision with
a much shorter length than the depth of the LET region. The normal depth where
the incident ion is stopped from the surface is referred to as a projected rang which
is much shorter than the integrated path length of the incident ion until stopped.
Figure 4.4 shows depth profiles of deposited energies by the electron excitation, the
nuclear collision, and the total loss.
All these collisions are dominated under surface resulting in electron excitation
and formation of vacancies and interstitial atoms (referred to as a Frenkel pair for
single vacancy and interstitial atom). Most of the exited or released electrons are
immediately deexcited or captured by ionized ions releasing energy as photons
including X-rays and phonons or heat. Similarly, most of the interstitial atoms
and vacancies are recombined. However, some interstitials and vacancies remain
making clusters such as vacancy clusters or voids and interstitial loops, referred to
as lattice defects which degrade materials properties, hardening, loss of ductility,
loss of thermal conductivity, and so on. The formation processes of various radiation
damages by energetic ion injection are out of scope of this book and not discussed
here. Nevertheless, they strongly influence PMI, in particular, hydrogen recycling
and retention which is discussed in Chaps. 6, 8, and 9.
Those energy loss processes that occurred at or near surface appear as PMI and
details are described in the following.
4 Responses of Plasma-Facing Surface to Power Load Given by Radiation …
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+
+
+
+
+
+
+
+
+
+
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e -
e -
e -
e -
e -
e -
e -
e -
e -
e -
e -
e -
e -
e -
e -
e -
e -
e -
e -
e -
e -
Scattered ion
Electron excitation
dominated area
Interstitial atom
Atomic collision
Vacancy
Incident ion
+ Ionized lattice atom
e - Excited electrons
Interstitial atom
Lattice atom
Vacancy
Fig. 4.3 Schematic drawing for energy loss process of energetic particle injected in a solid
become dominant. Because energy loss by the nuclear collision is much larger than
that of the ionization, the incident ion stops after repeating the nuclear collision with
a much shorter length than the depth of the LET region. The normal depth where
the incident ion is stopped from the surface is referred to as a projected rang which
is much shorter than the integrated path length of the incident ion until stopped.
Figure 4.4 shows depth profiles of deposited energies by the electron excitation, the
nuclear collision, and the total loss.
All these collisions are dominated under surface resulting in electron excitation
and formation of vacancies and interstitial atoms (referred to as a Frenkel pair for
single vacancy and interstitial atom). Most of the exited or released electrons are
immediately deexcited or captured by ionized ions releasing energy as photons
including X-rays and phonons or heat. Similarly, most of the interstitial atoms
and vacancies are recombined. However, some interstitials and vacancies remain
making clusters such as vacancy clusters or voids and interstitial loops, referred to
as lattice defects which degrade materials properties, hardening, loss of ductility,
loss of thermal conductivity, and so on. The formation processes of various radiation
damages by energetic ion injection are out of scope of this book and not discussed
here. Nevertheless, they strongly influence PMI, in particular, hydrogen recycling
and retention which is discussed in Chaps. 6, 8, and 9.
Those energy loss processes that occurred at or near surface appear as PMI and
details are described in the following.