Development of high energy laser resistance beam dump for the ITER Edge Thomson Scattering

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

no journal, , 

In ITER, 10 pulses of 5-J laser will be injected during its operation for 20 years. It was concerned that the surface damage was induced due to high incident laser energy density if conventional beam dump would be used. JAEA has proposed and modified the detailed shape of a new type beam dump in which the laser energy is reflected numerous times and absorbed gradually due to low absorptance of the S-polarized light. The new type beam dump withstands 10 pulses injection while conventional beam dump withstands 10 pulses (100 seconds) injection. In order to verify this design for drastically extending the beam dump life time, laser resistance test for molybdenum that is the beam dump material was carried out. As expected in design, beam energy absorption density is dominant factor for laser induced damage. Moreover, it was confirmed that interlaminating the bent sheets and shims and their diffuse bonding enable to manufacture complicated shape of the beam dump as designed.