TY  - THES
AU  - Koza, Yoshie
TI  - Performance of Metallic and Carbon-Based Materials Under the Influence of Intense Transient Energy Deposition
VL  - 4137
IS  - Juel-4137
SN  - 0944-2952
PB  - Techn. Hochsch. Aachen
VL  - Dr. (FH)
CY  - Jülich
M1  - PreJuSER-37539
M1  - Juel-4137
T2  - Berichte des Forschungszentrums Jülich
SP  - II, 140 S.
PY  - 2004
N1  - Record converted from VDB: 12.11.2012
N1  - Aachen, Techn. Hochsch., Diss., 2004
AB  - Intense energy is deposited on localized areas of the plasma facing materials under transient thermal loads such as edge localized modes (ELMS), plasma disruptions or vertical displacement events (VDEs) in a magnetic confined fusion reactor. Crack formation, thermal erosion and redeposition mainly take place under these conditions and may cause catastrophic damage in the materials. Dust formation associated with evaporation and liquid or solid particles emission are also serious issues to influence plasma contamination. In order to estimate the lifetime of the components during above mentioned events (ELMS, disruptions, VDEs), the thermal erosion mechanisms and performance of carbon-based and high Z materials have been investigated using energetic electron beam facilities. Moreover, a thorough calibration of an electron beam in the high heat flux facility JUDITH was done. For the evaluation of erosion data obtained in different test facilities several factors have to be taken into account. Different material erosion processes at identical heat loads induced by different facilities take place due to different beam generation and beam modes (static/scanned beam). The different degradation processes were created by different surface tensions and vapor recoil pressures at local spots in the loaded area. Molten and re-solidified material remained within the loaded area by fast scanning of the electron beam in JUDITH, which leaded to a rippling surface. Erosion scenarios have been elucidated on pure W and carbon-based materials. For W, the thermal erosion is initiated by convection of melt, strong evaporation or boiling processes. Moreover the formation of a vapor cloud was observed in the simulation experiments indicating vapor shielding on the surface. From screening tests on different high Z materials, pure Wwas found to show the highest resistance against thermal shock under plasma disruption conditions and are suitable for the components in Tokamak fusion reactors. A castellated structure was found to help reducing crack formation compared to monolithic structure. For carbon-based materials (isotropic graphite, $\underline{c}$arbon $\underline{f}$iber $\underline{c}$omposites (CFCs), Si-doped CFC), material erosion in different particle emission regimes, and characterization of emitted particles have been studied. "Small" and "Big" particle emission regimes have been identified under brittle destruction, which represents the combined action of sublimation, crack formation and ejection of solid particles. These regimes were related to the ejected particle size and maximum erosion depth. The resulting erosion patterns on the test samples and the morphology of the ejected particles differ significantly for the three materials. For both carbon and tungsten, preheating of samples before loading enhances material damages such as weight loss and crater formation.
LB  - PUB:(DE-HGF)11 ; PUB:(DE-HGF)3
UR  - https://juser.fz-juelich.de/record/37539
ER  -