| 摘要 |
PURPOSE:To prevent the clogging of a helium introducing pipe by providing a gate valve to the top end of a sample chamber and providing further a preparatory chamber for sample exchange to the upper part via a valve. CONSTITUTION:The preparatory chamber 14 for sample exchange which permits vacuum evacuation and purging by gaseous helium and is connected to the sample chamber 1 is provided. A gate valve 12 is provided between the chamber 14 and the chamber 1. A sample holder 6 is pulled up and is placed in the chamber 14 above the valve 12. The inside of both the sample chamber 1 and the preparatory chamber 14 is filled with the gaseous helium in this state and the valve 12 is open. The sample is then exchanged by shutting the valve 12 to isolate the chamber from the external air and opening an inlet and outlet 13 for sample exchange. The inside of the chamber 14 is then evacuated to a vacuum and is purged by the gaseous helium so as to be filled with the gaseous helium and thereafter the valve 12 is opened and the holder 6 is lowered to the measuring position. There is no possibility of the intrusion of the air into the chamber 1 at all according to such procedure. The clogging of the liquid helium introducing pipe 8 as a result of the freezing of the air incorporated into the pipe 8 so as to close the flow passage for the helium is entirely obviated. |
