Flux dependence of carbon chemical erosion by deuterium ions

化学スパッタリングの粒子束依存性

Roth, J.*; Preuss, R.*; Bohmeyer, W.*; Brezinsek, S.*; Cambe, A.*; Casarotto, E.*; Doerner, R.*; Gauthier, E.*; Federici, G.*; 東島 智; Hogan, J.*; Kallenbach, A.*; Kirschner, A.*; 久保 博孝; Layet, J. M.*; 仲野 友英; Philipps, V.*; Pospieszczyk, A.*; Pugno, R.*; Ruggiri, R.*; Schweer, B.*; Sergienko, G.*; Stamp, M.*

Roth, J.*; Preuss, R.*; Bohmeyer, W.*; Brezinsek, S.*; Cambe, A.*; Casarotto, E.*; Doerner, R.*; Gauthier, E.*; Federici, G.*; Higashijima, Satoru; Hogan, J.*; Kallenbach, A.*; Kirschner, A.*; Kubo, Hirotaka; Layet, J. M.*; Nakano, Tomohide; Philipps, V.*; Pospieszczyk, A.*; Pugno, R.*; Ruggiri, R.*; Schweer, B.*; Sergienko, G.*; Stamp, M.*

イオンビーム照射装置やトカマク装置では、ITERのダイバータ条件への外挿を目指し、化学スパッタリング率の粒子束依存性を測定して来た。しかし、取得データのパラメータが各測定で異なっていたため、従来のデータベースには大きなばらつきが見られた。国際トカマク物理活動(ITPA)の「スクレイプ・オフ層及びダイバータの物理」トピカルグループでは、参加する各装置から新たに較正・検討したデータを持ち寄り、イオンの入射エネルギー,材料の表面温度で規格化してデータの見直しを行った。これにより、ITERのダイバータ条件に近い高粒子束の領域では、化学スパッタリング率は粒子束の増加とともに減少し、その割合は粒子束の-0.54乗であることを明らかにした。

Chemical erosion of carbon has been studied in ion beam experiments, and the yield values are available as a function of ion energy and surface temperature. ITER divertor condition, however, cannot be simulated by ion beam. For extrapolating to ITER, the erosion must be investigated in plasma simulators and in SOL or divertors of present fusion devices. In the past, erosion values were reported, but the values showed a wide scatter as a function of ion flux, . Therefore, a joint attempt was made through the EU Task Force on Plasma-Wall Interaction and the International Tokamak Physics Activity (ITPA) to clarify the flux dependence. For each data point the local plasma conditions were normalized to impact energy of 30 eV, the data were selected for a surface temperature close to the maximum yield or to room temperature, and the diagnostic was calibrated in-situ. Through this procedure, the previous large scatter could be drastically reduced. A fit using Bayesian probability analysis was performed yielding a decrease of the erosion yield with at high ion fluxes.