Experimental study of Quantum Fluids Using a Rotational Cryostat

目前的研究项目旨在构建一个可旋转的低温恒温器，用于在几十毫开尔文到开尔文的温度下研究量子液体，并利用该装置计划和进行基础实验。这种类型的旋转低温恒温器是日本首次建造的，为了使项目有意义，在项目开始时就确定了研究对象和设备的主要特征。即以可控多孔玻璃中He膜的超流动性为主要研究对象。旋转速度被设计为从10-4 rad/秒的极低速度控制，这是产生与单个量子循环形成相对应的宏观循环所需的速度，到产生尽可能多的“自由”量子化涡所必需的相当高的速度。该装置建在上海理工大学a栋地下002室，在地下预留了一个专用的深坑，为该装置增加了屏蔽层，并建造了采用高科技气轴承和旋转系统的旋转结构。国产焦耳-汤姆逊预冷级稀释低温恒温器，专门用于旋转和试验，另外研制了固定式低温恒温器，用于预备实验。虽然本项目需要大量的技术和理论准备，但人力和资金并不多，我们已经实现了低温恒温器在100马克以下连续运行时的最高平稳转速6.2 rad/s。目前正在进行旋转振荡器的精确实验。本文在稳态低温恒温器中对多孔玻璃中形成的He薄膜的超流动性进行了研究，其热导率测量结果与之前的扭振实验结果一致。本文对多孔材料中He薄膜的超流动性和相相干性进行了理论研究，并研究了二维多孔弱结中π相移的有趣特征。通过对多孔玻璃薄膜制备过程的实验研究，可以真实地考虑多孔玻璃中可能出现的π相移的微桥现象。少

The present research project aimed to construct a rotatable cryostat for the study of quantum liquids at a few tens of milli Kelvin to kelvin temperatures and plann and perform fundamental experiments using this apparatus. This type of rotating cryostat is built for the first time in Japan and in order to make the project meaningfull the subject to study and the main features of the apparatus had been decided at the begining of the project. Namely the study of superfluidity in He films formed in the well controlled porous glasses has been selected as the main subject. The rotational speed was designed to be controlled from the very low speed of 10-4 rad/sec which is required for the production of a macroscopic circulation corresponding to formation of a single quantum circulation, to rather high speed which is neccesarry to produce as many 'free' quantized vortices as possible.The apparatus is built in the basement room 002 of the A-building of ISSP,a special pit is prepared with a RF … More shield for this apparatus and the rotating structure with high tech air bearing and turning system is built. A diolution cryostat with Joule Thomson precooling stage is home made specially for rotation and tested, in addition another cryostat for stationary test purposes is built and used for preparatory experiment.Although the project demands quite a lot of technical and theoretical preparations without much manpower nor funding, we have achieved the highest smooth rotation speed of 6.2 rad/sec while continuous operation of the cryostat below 100 mK.Currently a precice experiment of tortional oscillator is being prepared under rotation. Which has been performed to study the nature of the superfluidity in thin He films formed in well controlled porous glasses in a steady cryostat where thermal conductivity measurements yealding consistent result with former tortional oscillator experiment.A theoretical study of the nature of superfluidity and phase coherency in He films in porous materials has been being put forth and an interesting feature of pi phase shift across a two dimensional porous weak junction is studied.An experimental study of thin porous glass film production enabled the realistic consideration of the micro bridge out of porous glass with the possible pi phase shift. Less