62
4 Responses of Plasma-Facing Surface to Power Load Given by Radiation …
Fig. 4.13 Energy
distribution of secondary
electrons induced by
injection of Li, He, Ne, and
Ar ions on Cu(100) for
5 keV incident energy.
Spectra are corrected by the
energy transmission of the
analyzer (reprinted with
permission from [26])
induced by injection of Li, He, Ne, and Ar ions on Cu(100) for 5 keV incident energy
[26]. Heavier the incident ion, the secondary electrons with higher energy increase,
because interactions between the incident ion and the target occur in the shallower
region resulting in less energy loss of the secondary electrons. Together with the
kinetic electron emissions, X-rays or photons are emitted including characteristic
X-rays (like the Auger electron emission).
Generally, energetic electron injection gives similar phenomena to those given
by energetic particle injection. They are reflection; emission of secondary particles including secondary electrons, photons, and phonons; sputtering of constituent
elements of target materials; and electron-induced desorption. Because of the much
lower mass of an electron, however, these emissions are less appreciable compared
to ion-induced emissions. Nevertheless, huge incident electron flux accompanying
huge ion flux at PFS could have a significant influence on PMI in a reactor. Until
now the effect of the electron has not been considered or examined because electron
flux in current tokamak is not so high as that in a reactor.
In tokamak discharges, runaway electrons of which energy sometimes exceed
MeV appear. Owing to their very high energy, material damages like arching and hot
spot and resultant local melting give a significant influence on materials integrity.
4.4.2 Photon Emission
As described above, energetic particle injection always accompanies emissions of
photons including X-rays, UV, Visual light, and even infrared radiation by the temperature rise of the target. Detection of characteristic X-rays under high-energy proton
is used as an analysis technique of elements in materials referred to as PIXE (ProtonInduced X-ray Emission). The photoemission could induce photoelectrons. The
thermionic emission appears if deposited energy by injected ions is so large that
the target temperature becomes quite high.
4 Responses of Plasma-Facing Surface to Power Load Given by Radiation …
Fig. 4.13 Energy
distribution of secondary
electrons induced by
injection of Li, He, Ne, and
Ar ions on Cu(100) for
5 keV incident energy.
Spectra are corrected by the
energy transmission of the
analyzer (reprinted with
permission from [26])
induced by injection of Li, He, Ne, and Ar ions on Cu(100) for 5 keV incident energy
[26]. Heavier the incident ion, the secondary electrons with higher energy increase,
because interactions between the incident ion and the target occur in the shallower
region resulting in less energy loss of the secondary electrons. Together with the
kinetic electron emissions, X-rays or photons are emitted including characteristic
X-rays (like the Auger electron emission).
Generally, energetic electron injection gives similar phenomena to those given
by energetic particle injection. They are reflection; emission of secondary particles including secondary electrons, photons, and phonons; sputtering of constituent
elements of target materials; and electron-induced desorption. Because of the much
lower mass of an electron, however, these emissions are less appreciable compared
to ion-induced emissions. Nevertheless, huge incident electron flux accompanying
huge ion flux at PFS could have a significant influence on PMI in a reactor. Until
now the effect of the electron has not been considered or examined because electron
flux in current tokamak is not so high as that in a reactor.
In tokamak discharges, runaway electrons of which energy sometimes exceed
MeV appear. Owing to their very high energy, material damages like arching and hot
spot and resultant local melting give a significant influence on materials integrity.
4.4.2 Photon Emission
As described above, energetic particle injection always accompanies emissions of
photons including X-rays, UV, Visual light, and even infrared radiation by the temperature rise of the target. Detection of characteristic X-rays under high-energy proton
is used as an analysis technique of elements in materials referred to as PIXE (ProtonInduced X-ray Emission). The photoemission could induce photoelectrons. The
thermionic emission appears if deposited energy by injected ions is so large that
the target temperature becomes quite high.