| 摘要 |
The melting point of the metallic material lies between the operating temperature of the cathode and the melting point of the refractory material. It may be deposited from vapour in a vacuum, or it may be a metal powder. Alternatively it may take the form of a thin plate or an approximately rectangular strip covering in the central region 40-70% of the surface between the piece (1) and the support (13). The material may be magnetic, notably nickel to allow the positioning of a strip by an electromagnet but other metals or alloys may be used such as chromium, vanadium and rhenium. |
