Chevron beam dump for ITER edge Thomson scattering system

Yatsuka, Eiichi; Hatae, Takaki; Vayakis, G.*; Bassan, M.*; Itami, Kiyoshi

This paper contains the design of the beam dump for the ITER Edge Thomson Scattering (ETS) System and mainly concerns its lifetime under the harsh thermal and electromagnetic loads as well as tight space allocation. The lifetime was estimated from the multi-pulse laser-induced damage threshold. In order to extend its lifetime, the structure of the beam dump was optimized. A number of bent sheets aligned parallel in the beam dump form a shape called a chevron which enables it to avoid the concentration of the incident laser pulse energy. The chevron beam dump is expected to withstand thermal loads due to nuclear heating, radiation from the plasma and numerous incident laser pulses throughout the entire ITER project. Structural analysis was also carried out in case of electromagnetic loads during a disruption. Induced stress is significantly less than the yield strength. Therefore, it is expected that the chevron beam dump will work under the ITER's environment.