Radioactive gas solidifying device

The device of the present invention, a sputtering electrode comprises a cylindrical electrode main body made of a transition metal, electrode caps each made of a transition metal and connected by welding to the upper and the lower portions of the main body and a plurality of annular grooves formed to the outer surface of the electrode main body. The electrode main body and the electrode cap are connected by welding at the portions of the annular grooves, and rare earth elements are filled in the annular grooves. Then, when operation is conducted for a long period of time, the thickness of the electrode is gradually reduced by sputtering. When the rare earth element in the annular grooves are completely eliminated by the reduction of the thickness, radioactive gases are no more injected into the accumulated metal layers of sputtered metal formed at the surface of the ion injection electrode, to reduce the processing efficiency. By detecting the reduction and interrupting the operation directly, the reduction of the wall thickness in the welded portion between the main body and the electrode cap is prevented. In this way, it is possible to prevent the leakage of cooling water therefrom and abnormal electric discharge caused thereby, to enable stable operation for a long period of time. (T.M.)