NUMERICAL SIMULATION OF THE EFFECT OF AN ELECTRON BEAM ON THE SURFACE OF MATERIALS

Kamilla Ashurova,
TUSUR, Tomsk, Russian Federation

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Aleksandr Pushkarev 2020-09-16 22:17
Figure 5b - temperature of steel?
For steel A 276 temperature of melting 1425-1510 C

KA
Author
Kamilla Ashurova 2020-09-16 22:17
Aleksandr Pushkarev 2020-09-16 15:57
Figure 5b - temperature of steel? For steel A 276 temperature of melting 1425-1510 C

Yes, it is the temperature of steel. And I also agree that melting temperature is in this range, but on the figure it is shown in Kelvins. And the peak in this graph is associated with the sputtering of the target. After 200 microseconds the steel starting to crystalize.

sz
shijian zhang 2020-09-17 15:03
based on Fig. 2.
1. can we say that the electrons just reach the surface of material at the time when surface temperature starts to increase? and the several us before this time is the flight time of electrons from gab to surface of material?

based on Fig. 2 and Fig. 5
2. the surface temperature decreases immediately when Ig decrease (at ~200 us). Ig is still positive after that. it means we still have power source. why dose surface temperature decrease when we have power source? is it because more energy pass to sub surface than energy input´╝čdid you consider the radiation and convection as boundary condition at the surface (L=0)?

KA
Author
Kamilla Ashurova 2020-09-17 15:22
shijian zhang 2020-09-16 15:57
based on Fig. 2. 1. can we say that the electrons just reach the surface of material at the time when surface temperature starts to increase? and the several us before this time is the flight time of electrons from


1. Heating of the material starts immediately after the interaction of the electron beam with its surface. Before that, the material is at room temperature. The contribution of the electron beam energy to the material ends after the end of the current in the accelerating gap.

2. After 200 μs, the beam current pulse does not end, and the beam energy continues to be deposited into the sample. Even if the duration of the discharge current pulse does not exceed 200 μs, the processes in the accelerating gap continue. This energy contribution can be considered uncontrollable, and here you are right - the rate of energy input after 200 μs is several times less than before 200 μs. Since the temperature of the sample surface is very high by the instant of the beam current pulse corresponding to 200 μs, this leads to the fact that a decrease in the rate of energy input leads to a decrease in the sample temperature. The system tends to thermal equilibrium when the amount of energy input is equal to the amount of energy removed from the sample. In this case, the higher the sample surface temperature, the higher the rate of output energy. Energy removal is provided by three mechanisms: a) heat transfer, which is proportional to the thermal conductivity coefficient and the temperature difference between the surface and the sample (Q ~ K · Δt); b) radiation (the Stefan-Boltzmann law, from which it is known that heat removal by radiation is proportional to the body temperature to the fourth power S = σ · T4); c) evaporation of the material. In this case, radiation was not taken into account

sz
shijian zhang 2020-09-18 10:33
Kamilla Ashurova 2020-09-17 15:22
1. Heating of the material starts immediately after the interaction of the electron beam with its surface. Before that, the material is at room temperature. The contribution of the electron beam energy to the material ends after the end


thanks for your reply.
i want to make it more clear about my first question. as we can see on Fig.2, the surface temperature did not raise up immediately (at 0 us). it starts to increase at about 10 us. and during 0-10 us we have discharge and gap current. is it reasonable to say that electrons was flying to the surface during this time?

KA
Author
Kamilla Ashurova 2020-09-19 02:56
shijian zhang 2020-09-18 10:33
thanks for your reply. i want to make it more clear about my first question. as we can see on Fig.2, the surface temperature did not raise up immediately (at 0 us). it starts to increase at about 10

Actually, it is not so. Because electrons reach the surface for the fraction of microsecond. On figure 2, you may not see how temperature increases for the first 10 μs because of the pyrometer, which measures the temperature. Because it starts recording temperature only from 300 grades. And after the surface heated for 300 grades, it starts indicating on the graph.