大口径实验杜瓦瓶漏热分析与防护

<正>介绍20升大口径玻璃实验液氦杜瓦瓶漏热的分析计算。指出漏热的主要途径是杜瓦端盖和杜瓦金属套向液氦面的辐射     

液氦输送技术

正确掌握液氦输送方法，对减少液氦预冷量，充分利用氦气冷量和提高液氦输送效率有着十分重要的经济意义，对液氦输送管的结构特点和使用要求及液氦预冷，液氦的输送方法和几种特殊容器的输送方法做了介绍。     

塑料杜瓦的研制

塑料杜瓦适合在大型脉冲磁体中使用，韭且可用它进行电绝缘和非磁性感应，但存在三个需要解决的问题；(1)塑料壁对氦气的透气性；(2)室温与液氦温度问热应力的恶化；(8)液氦温度下粘接的机械性能差。     

提高低温玻璃钢真空气密性的方法之研究

一、前言在玻璃钢液氦无磁杜瓦及无磁制冷机的研制中常常遇到低温玻璃钢的气密性问题。我们研制成功的玻璃钢液氦无磁杜瓦,其绝热性能达国际先进水平。然而,有关低温玻璃钢的气密性问题尚待进一步研究。尽管许多研究者关注玻璃钢的放气及其     

玻璃钢液氦容器绝热结构实验研究

一、引言 玻璃钢因玻璃纤维的增韧和增强作用，使其在低温环境下具有良好的热物性和力学性能，引起了从事研究生物磁和超导磁体技术人员的重视，并逐步获得应用。人们知道，超导磁力仪应用的可靠性、经济性与使用周期，除了与超导器件的可靠性和稳定性有关外，还与盛装液氦的无磁杜瓦容器的可靠性及绝热性能有关。     

液氦自动输送系统

术文介绍研究用小型杜瓦(50升)液氦自动输送系统，该系统设备简单，输液安全、可靠。     

超导HWR腔垂直测试低温系统试验研究

中国科学院先导科技专项ADS(Accelerator Driven Suberitical,ADS)嬗变系统中超导HWR(half-wave resonator,HWR)腔垂直测试需低温系统维持4.2 K(液氦)的低温环境,低温系统降温过程包括氮气置换、液氮预冷、氦气置换和液氦冷却。通过实验建立了低温系统降温4个阶段不同测点温度随时间的变化规律,在此基础上,计算了液氦的消耗速率和杜瓦的静态热负荷,分析了低温系统在稳定工作状态时最佳的液氦补液时间间隔。结果表明:该低温系统满足超导HWR腔垂直测试需求,消耗液氮约175 kg、液氦约2 048 L,低温系统稳定工作时液氦体积消耗速率为32 L/h,杜瓦静态热负荷为21.36 W,液氦合理补液时间间隔为4 h,为后续超导HWR腔垂直测试提供了保障。     

中性束注入器低温冷凝泵抽气性能测试平台的研制

中性束注入器用液氦低温冷凝泵抽气性能的主要影响因素是低温冷凝抽气面温度,单位时间进气量和被冷凝的气体总量.本文采用流量计法抽速测试装置;同时依据液氦温度与其饱和蒸汽压之间的变化规律,系统中采用了氦气出气压力控制单元,通过调节液氦杜瓦内压力改变液氦的温度从而实现控制液氦低温冷凝面温度;且采用压电晶体阀对单位时间进气量以及被冷凝气体总量进行精确控制;使用ZJ-12型B-A规测量测试装置内真空度.设计了仿真中性束注入器用的低温冷凝泵的测试泵,对其进行ANSYS热力学分析,从而计算出该泵的低温冷凝面积.加工组装了测试平台,并在中性束注入器的工作条件下进行实验,得到测试泵的对氢抽速为940 L/s,表明该系统能够满足测试要求,为中性束注入器低温冷凝泵设计提供实验和理论依据.     

大型空间环境模拟器设备液氮制冷系统杜瓦管的研制

液氮系统是大型空间环境模拟设备中的主要分系统之一，在大型空间模拟器的液氮流程中，采用杜瓦管供液的结构形式，也是近年来国外大型空间模拟器中所采用的主要供液方式，介绍了大型空间环境模拟器液氮制冷系统中杜瓦管的作用、结构、使用情况及特点，并根据现场调试，维护等自身因素限制，设计了一种比较简便实用的测试真空试件，经过现场对杜瓦管的调试验收，使杜瓦管的真空性能得到保证，经历了多项试验，杜瓦管始终处于良好使用状态，方便而可靠地保证了对系统，热沉等分系统的供液。     

50 kA超导变压器杜瓦及高温超导电流引线的设计与优化

CICC超导导体性能测试用50 kA超导变压器由初级线圈和次级线圈组成,初级线圈浸泡在4.2 K液氦低温杜瓦中,次级线圈为CICC导体采用4.2 K/354 637 Pa超临界氦迫流冷却,液氦和超临界氦均由500 W/4.5 K制冷机提供,变压器低温杜瓦的理论液氦蒸发率为1.52 L/h。为减少电流引线漏热,超导变压器采用B i-2223/AgAu高温超导(HTS)二元电流引线,并且在颈管中部设计了一个新型的直接用液氮冷却的热截流装置来截断电流引线高温端的热流;最后对铜电流引线部分进行了尺寸优化计算,得到最佳截面积和直径分别为28 mm2和6 mm。     

AMS-02超导磁体中超流氦加注过程研究

论述了AMS-02超导磁体中超流氦的加注过程,进行了各个环节压降和温降的计算分析,并用图表表示了在不同质量流量加注超流氦工况下管路系统中氦工质的速度、压力、温度和含气量的变化情况.计算结果表明,氦工质从液氦主杜瓦加注到磁体杜瓦的过程中,其压力和温度不断降低,而含气量不断增加.同时也表明在节流阀VVP9中实现了常流氦向超流氦的转变和质量流量的控制.     

Design and performance of cryogenic enclosures for long duration testing of large samples

We have designed a large helium dewar as part of an experiment to investigate gravitational radiation. Two such dewars have been constructed. Our use requires a nonmagnetic dewar to cool an aluminium antenna of approximately 5000 kg to below helium temperatures and to keep the antenna in a stable low temperature environment for extended time. This requires a low temperature volume of 1.5 m inner diameter and 3.1 m length and a cooling system capable of efficiently removing the room temperature enthalpy of 8.5 × 10⁸ J. Our solution to this problem is of wider application than simply gravity wave detection so we have discussed the design philosophy in some detail. As constructed, the apparatus uses less than 1 l of helium per hour when cold.     

Investigation of a rotating liquid helium transfer coupling

A bayonet coupling of a stationary transfer tube with a liquid helium, rotating dewar, horizontal neck has been tested. A relation between the heat leak to liquid He in the coupling and the dewar rotation speed at different bayonet lengths has been derived.     

Efficient helium recondensing using a 4 K pulse tube cryocooler

This paper introduces helium recondensing in a 4000 l dewar using a 4 K pulse tube cryocooler at Amundsen-Scott research station at the South Pole. The helium dewar has a normal boil-off rate of 14 l/day. Two features of cooling the dewar neck by helium vapor and precooling helium gas to be liquefied ensured high efficiency of the pulse tube recondenser in this application. The liquefier/recondenser has being successfully operating in the dewar at South Pole station since February 2005. It not only maintains zero boil-off of the dewar, but also liquefies helium gas supplied from outside of the dewar with a rate around 2.7 l/day.     

Operating modes and cooling capabilities of the 3-stage ADR developed for the Soft-X-ray Spectrometer instrument on Astro-H

A 3-stage adiabatic demagnetization refrigerator (ADR) (Shirron et al., 2012) is used on the Soft X-ray Spectrometer instrument (Mitsuda et al., 2010) on Astro-H (Takahashi et al., 2010) [3] to cool a 6 × 6 array of X-ray microcalorimeters to 50 mK. The ADR is supported by a cryogenic system (Fujimoto et al., 2010) consisting of a superfluid helium tank, a 4.5 K Joule–Thomson (JT) cryocooler, and additional 2-stage Stirling cryocoolers that pre-cool the JT cooler and cool radiation shields within the cryostat. The ADR is configured so that it can use either the liquid helium or the JT cryocooler as its heat sink, giving the instrument an unusual degree of tolerance for component failures or degradation in the cryogenic system. The flight detector assembly, ADR and dewar were integrated into the flight dewar in early 2014, and have since been extensively characterized and calibrated. This paper summarizes the operation and performance of the ADR in all of its operating modes.     

Fabrication of stainless steel dewars for experiments at low temperature

A basic stainless steel dewar design is described which can be used in a variety of experimental situations. With a 63.5 mm ($\text{2}\text{1}\text{2}\text{″}$) diameter neck, the dewar holds 4.8 litres of liquid helium for a period of 8 days. A large multi-purpose dilution refrigerator which has evolved from the basic design is also described. Liquid helium consumption of the dilution refrigerator is 18 1/week.     

Portable helium dewars for use with superconducting magnetometers

Simple helium dewars have been constructed using gas-cooled radiation shields and multi layer aluminized plastic insulation. They will retain one litre of liquid for up to 40 hours The shields may be made mostly non-conducting so the dewar can be used with ultrasensitive superconducting magnetometers. For most other applications thin sheet metal such as copper or aluminium is suitable for the shields.     

A glass helium cryostat for optical and magneto-optical studies

A glass helium cryostat with copper shield for optical and magneto-optical studies is described. The shield-insert placed in the nitrogen dewar without hindering visual observation at the liquid helium level, prevents scattering of light by the bubbles of boiling nitrogen.     

A gas-thermostated hydrogen-helium portable 100 l dewar flask

A dewar of 100 l capacity for storing liquid hydrogen and helium which is insulated by evaporating gas has been constructed. Its distinctive features are simplicity in construction and light weight which enables it to be easily manually transported. Its main parameters are: empty flask weight 42.5 kg, hydrogen evaporation 0.8% daily, and helium evaporation 1.8% daily. The result of heat parameters values measured for the flask are given.     

Thermodynamic performance of the 3-stage ADR for the Astro-H Soft-X-ray Spectrometer instrument

The Soft X-ray Spectrometer (SXS) instrument (Mitsuda et al., 2010) [1] on Astro-H (Takahashi et al., 2010) [2] will use a 3-stage ADR (Shirron et al., 2012) to cool the microcalorimeter array to 50 mK. In the primary operating mode, two stages of the ADR cool the detectors using superfluid helium at ⩽1.20 K as the heat sink (Fujimoto et al., 2010). In the secondary mode, which is activated when the liquid helium is depleted, the ADR uses a 4.5 K Joule–Thomson cooler as its heat sink. In this mode, all three stages operate together to continuously cool the (empty) helium tank and single-shot cool the detectors. The flight instrument – dewar, ADR, detectors and electronics – were integrated in 2014 and have since undergone extensive performance testing. This paper presents a thermodynamic analysis of the ADR’s operation, including cooling capacity, heat rejection to the heat sinks, and various measures of efficiency.