Shinku

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A new diffusion pump fluid “Lion S”, whose main component is monoalkylnaphthalene, has been evaluated both in a metal diffusion pump and in a Hickman type one. The ultimate pressure and the oxidation stability of this fluid were tested and compared with those of silicone fluid DC 705. The ultimate pressure experimentally obtained for Lion S in the metal pump system with a water-cooled chevron baffle was 6×10^-9 Torr with the normal-type B-A gauge and 8.4×10^-9 Torr with the nude-type one. In the case of the Hickman pump system, the lowest pressure obtained without a trap was 67×10^-10 Torr which was the same value as that obtained for DC 705. Oxidation stability tests were made by admitting air into the pump system in operation up to the atmospheric pressure and repeated twice for 1 minutes, twice for 5 minutes, once for 10 minutes, and finally once for half an hour. Vacuum restoration was confirmed after evacuating and baking the test dome each time air was admitted. As a result, an ultimate pressure of 5×10^-8 Torr was obtained, even after the test dome and the pump were exposed to air for almost an hour in all, by degassing the test system.

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