液氧密度标准计量装置的研制

研制的液氧密度标准计量装置主要由液氧容器、专用恒温器、测控系统、质量测量系统、PC机组成.分析和评定了温度测量不准确度,考核了液氧密度计量装置的性能.液氧密度标准计量装置在温度90～100 K、压力0.1～0.6 MPa条件下,其扩展不确定度(K=3)沸点条件下不大于0.3kg/m3,沸点之外不大于0.5 kg/m3.     

EAST外杜瓦系统泄放装置的设计与实验研究

为保护过压状态下EAST装置的外杜瓦系统,在外杜瓦系统上设计了爆破片过压泄放装置,经ANSYS结构分析确定了爆破片的型式和参数,基于分析结果试制了316LN的爆破片装置,并通过实验进一步验证了设计方案的可行性与可靠性。实验结果表明,设计方案合理,能为同类装置的过压安全保护和研发提供借鉴。     

高电流密度超导储能磁体的研制

分析了不同结构超导储能磁体的特点,针对储能量为MJ量级的超导储能磁体计算了漏磁场分布和超导材料的利用率,提出了储能为1 MJ的单螺管型超导储能磁体的设计方案。采用窄液氦通道技术,利用多芯NbTi/Cu复合超导线,研制了储能量为1 MJ的紧凑型超导储能磁体。磁体内径为439 mm,外径为600 mm,高为550 mm。在运行电流为305A时,磁体的最大磁场为4.9 T,中心磁场为4 T。对超导磁体的试验结果表明,磁体的最大运行电流为303 A,放电功率为100 kW。研制的超导储能磁体可作为恒压/恒功率放电的不间断电源的关键部件。     

超导重力梯度勘探系统

超导重力梯度仪具有高灵敏度、高分辨率、性能稳定和宽动力范围等优点,它涉及的学科很多,研发难度相当大。以Maryland大学研制的低温超导重力梯度仪为例,讨论了超导加速度计、超导电路、线性加速度计、角加速度计、低温恒温器等超导重力梯度仪主要构成部件的组成和测量原理,并介绍了其预期的性能和主要的误差源。     

实现高精度红外探测的冷光学技术

高灵敏度、低噪声是红外探测技术的必然要求,实现这一目标的有效手段之一就是冷光学技术。冷光学技术的成熟又进一步促进了红外探测的快速发展。通过查阅相关文献资料,对国外典型地基大口径望远镜制冷红外设备的冷光学部分作了简要介绍,从工程应用的角度阐述了红外光学技术的各要素,如低温恒温器制作、光学和机械结构设计、探测器安装等在冷光学处理中的设计要点和注意事项。     

Thermal contact conductance of pressed contacts at low temperatures

The influence of variations of interface temperature in the range 50-300 K on the thermal contact conductance between aluminium and stainless steel joints was determined. Predictions were done by modeling the deformation at the interface for different values of surface finish and contact pressure over the range of interface temperatures. Both elastic and plastic deformation was considered. Experiments were carried out in a closed loop cryostat and the results were shown to compare well with the predictions. A reduction of the interface temperature resulted in a smaller value of thermal contact conductance. Interfacial pressure variation had much lower influence at the smaller value of temperatures. The role of surface roughness at the contact was also seen to be less significant at lower interface temperatures and the zone of hysteresis was smaller. A correlation was developed for estimating thermal contact conductance at joints over this temperature range. An explicit dependence of contact conductance on temperature was not seen to be necessary as long as the changes in the hardness and thermal conductivity of the material with temperature are incorporated in the correlation.     

An inexpensive liquid helium level sensing unit

Two units to measure the level of liquid helium in a superconducting magnet and in a storage dewar are described.     

Can you trust your cryostat? Reproducibility of cryostat section thickness

Reproducibility of cryostat section thickness is required for valid quantitative microscopy. This is generally pursued by motorized sectioning using a low but constant speed. The purpose of our study was to compare variation in section thickness between motorized and manual cryostat sectioning. Serial sections were cut from a frozen block of homogenized tissue on different days. Lactate dehydrogenase activity was histochemically detected and calibrated absorbance measurements were taken. The coefficients of variation of measurements was 9.7% for motorized sectioning and 3.3% for manual sectioning. In conclusion, section thickness is similarly reproducible after manual sectioning compared with motorized sectioning, if not better.     

基于闭环制冷机的平衡氢三相点复现装置

为了解决平衡氢三相点复现装置复现难度大、耗时长、效率低的问题,研制了基于闭环GM制冷机的新型平衡氢三相点复现装置。采用准绝热方法复现平衡氢三相点;基于Labview程序,实现了复现过程的自动测量与控制。该套装置不仅提高了工作效率,而且提升了复现性。实验结果表明:该套系统平衡氢三相点的复现性优于0.05 mK,标准不确定度优于0.1 mK。     

Design Evolution and Analysis of the ITER Cryostat Support System

The cryostat is a vacuum tight container enveloping the entire basic systems of the ITER tokamak machine,including a vacuum vessel,a superconducting magnet and thermal shield etc.It is evacuated to a pressure of 10~(-4)Pa to limit the heat transfer via gas conduction and convection to the cryogenically cooled components.Another important function of cryostat is to support all the loads from the tokamak to the concrete floor of the pit by its support system during different operational regimes and accident scenarios.This paper briefly presents the design evolution and associated analysis of the cryostat support system and the structural interface with the building.