Apparatus for plasma experiment in the region of the supercritical point of mercury

An apparatus to study the change of electron state around the critical point of mercury was constructed. The critical point of mercury is at T asymptotically equals 16000K and P asymptotically equals 1600 atmosphere. A pressure vessel is required for the experiment. A capsule which contained mercury was set in a pressure vessel filled with compressed argon gas. The capsule was heated with a heater, and the required temperature was obtained. Optical measurement was made through sapphire windows. Detail of construction is described in this paper. A compressor used to compress the argon gas was a three stage compressor of air-oil-gas made by HASKEL Co., in U.S.A. It consisted of a hydraulic pump, a gas booster and an intensifier. Estimation of strength according to the Japanese law is required. Relief valves were equipped for safety. Strength estimation of pipings is also required. A barrier wall was made for protection in case of emergency. The pressure vessel was made of Be-Cu alloy, which has good cooling characteristics. Safety investigation of the vessel is described. A water jacket was provided outside of the vessel for cooling, and sapphire windows were supported by BeA-25 (Be-Cu) plugs. The mercury was contained in a N6 capsule sealed by sapphire rods. Various regulations by law were required. (Kato, T.)