Precise low temperature and high pressure apparatus using herium on an experimental basis

低温高压技术已被证明是研究高tc超导体、重费米子化合物和有机导体等强相关电子系统基本问题的有力工具。低温高压技术的主要困难之一是获得均匀的压力，在这种压力下给出可靠的结果。为了在低温下产生静水压力，我们试图在实验的基础上用氦气制造一个高压装置。第一步，为了测量^3He的A相超流分数，我们以^3He为传压介质，制作了超导磁体结合的高压设备。它可以在高达29巴的高压和低至34mK的温度下工作。接下来，我们试图制造一种装置，通过这种装置，可以在低温下对脆弱的单晶施加单向压力。在1K以下的单轴应力下，用该仪器测量了α -(BEDT-TTF)_2 KHg(SCN)_4在导电面上的电阻率。我们使用了冷波纹管，在室温下通过改变_4He气体来改变压力，因为液体_4He不会凝固到25bar。波纹管的有效直径约为70mm，压力放大约为100-200。类似的波纹管适用于高压产生高达3OGPa使用金刚石砧结合稀释冰箱和超导磁体。该系统有望成为研究与基本问题相关的近期和未来主题的有力工具。

High pressure techniques at low temperatures have been proved to be very powerful tools in studies of recent topics related to the fundamental problems in strong correlated electron systems such as high-Tc superconductors, heavy fermion compounds and organic conductors. One of the main difficulties in high pressure techniques at low temperatures is to obtain uniform pressures at which reliable results are given, In, order to generate hydrostatic pressures at low temperatures we try to make a high pressure apparatus using herium on a experimental basis.In the first step, in order to measure the superfluid fraction of the A phase of ^3He we made a high pressure equipment combined with a superconducting magnet using ^3He as a pressure transmitting medium. It works at high pressures up to 29 bar and at temperatures down to 34mK.Next, we tried to make an apparatus by which the unidirectional pressure can bbe applied on a fragile single crystal at low temperatures. Using this apparatus we made resistivity measurements of alpha -( BEDT-TTF )_2 KHg(SCN)_4 in the conducting plane under uniaxial stress below 1K.We used the cold bellows in which a pressure is variable by changing _4He gas at room temperature because of no solidification of liquid _4He up to 25 bar. The effective diameter of the bellows is about 70mm and the pressure amplification is about 100-200.Similar bellows are adapted to high pressure generation up to 3OGPa using a diamond anvils combined with a dilution refrigerator and a superconducting magnet. This system is expected tobe a powerful tool in studies of recent and future topics related to the fundamental problems.