Experimental study of Quantum Fluids Using a Rotational Cryostat

本研究项目旨在构建一个可旋转的低温恒温器，用于研究几十毫升开尔文到开尔文温度和平面的量子液体，并利用该装置进行基础实验。这种旋转式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的课题和设备的主要特点。也就是说，我们选择了控制良好的多孔玻璃中形成的氦薄膜的超流性作为主要研究对象。旋转速度被设计为从产生与形成单个量子环流相对应的宏观环流所需的10-4rad/s的极低速度到相当高的速度，以产生尽可能多的自由量子化涡旋。该装置建在ISSP A楼的地下室002，用RF…准备了一个特殊的凹坑为该装置建造了更多的屏蔽层，并采用了高科技气浮和转动系统的旋转结构。自行研制了一台具有焦耳-汤姆逊预冷级的旋转恒温器并进行了试验，另外还建造了一台用于静态试验的恒温器用于前期实验。虽然该项目需要大量的技术和理论准备，但在没有太多人力和资金的情况下，我们已经实现了最高的平滑转速6.2rad/s，同时恒温器在100mK以下连续运行。目前正在进行扭转振荡器的精密旋转实验。在稳定的恒温箱中研究了在控制良好的多孔玻璃中形成的He薄膜的超流性的性质，其中热导率的测量结果与以前的扭转振子实验结果一致。对多孔材料中He薄膜的超流性和相干性进行了理论研究，并研究了跨二维多孔弱结的pi相移的有趣特征。对多孔玻璃薄膜制备的实验研究使人们能够现实地考虑多孔玻璃中可能存在的pi相移的微桥。较少

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