高精度低温温度测量与控制系统实验研究

发布时间：2018-03-26 23:04

本文选题：低温测量　切入点：低温恒温器　出处：《华中科技大学》2014年硕士论文

【摘要】：在低温物理实验中，温度的测量是最基本的测量。与常温下的温度测量相比，低温系统中的要求更为严格。在常温下一些不被重视的问题如引线漏热、辐射热、焦耳热和接触热阻等，在低温下则变得重要起来。GM制冷机冷却的低温恒温器在很多领域得到了广泛的应用，它具有结构简单、操作方便、运行和维护成本低的优点。但是，受限于GM制冷机的自身结构和工作原理，，其冷头处温度波动较大，并且有振动。对于温度稳定性要求较高的场合，这种温度波动是相当不利的。基于以上分析，本文进行了制冷机冷却的低温温度测量和控制系统实验研究，具体工作内容如下：针对制冷机冷头的温度波动模型，从理论上进行了分析求解。根据解析解可知，温度波动的幅值主要受材料热扩散率和冷头波动频率的影响。热扩散率越小、波动频率越大，相同的导热距离上，温度波动的幅值也越小。分别进行了热阻实验，氦罐实验，氦罐和热阻相结合的实验。实验结果显示，使用热阻的方案可以有效抑制温度波动，且恒温器整体结构更简单、操作更方便。在氦罐实验中，除4.2K外，其他各点处，温度波动并不能得到很好的抑制。在氦罐和热阻结合的实验中，温度波动峰峰值控制在3mK以内。对制冷机冷却的低温恒温器中温度的控制进行了实验研究。通过PID控制的方法，控制样品架上温度的升降温速率。采集了PID控制时样品架上温度波动的短期稳定性和长期稳定性数据。实验结果显示，受限于制冷机本身性能，恒温器中存在一个最大降温速率和一个最慢升温速率。采用PID控制的方法可以很好的控制样品架上匀速升降温。采用PID控制，样品架上长期稳定性良好，4.2K处温度波动控制在±1.5mK，温度的标准偏差为0.339mK。设计了制冷机停开机实验方案并进行简单的前期实验验证。测量了连接部件之间总的接触热阻并进行分析。在制冷机停开机实验中，制冷机停机之后，样品架上温度保持在7K附近，波动范围为6.9990K-7.0030K，稳定时间约为650秒。稳定时间和控温稳定性符合实验要求。
[Abstract]:In the low temperature physics experiment , the temperature measurement is the most basic measure . Compared with the temperature measurement at normal temperature , the requirement of the low temperature system is more strict . The low temperature thermostat cooled by the GM refrigerator is widely used in many fields .

According to the analytical solution , the amplitude of the temperature fluctuation is mainly influenced by the thermal diffusivity of the material and the fluctuation frequency of the cold head . The experimental results show that the temperature fluctuation can be effectively suppressed by using the thermal resistance scheme .

The control of temperature in a cryogenic thermostat cooled by a refrigerator is experimentally studied . The temperature fluctuation of the sample holder is controlled by PID control . The short - term stability and long - term stability data of the temperature fluctuation in the sample holder are controlled by PID control . The experimental results show that the temperature fluctuation of the sample holder is controlled by PID control .

This paper designs a test scheme for the start - up of a refrigerator and performs a simple preliminary experiment . The total contact thermal resistance between the connecting parts is measured and the analysis is carried out . After the refrigerator is stopped , the temperature of the rack is kept close to 7 K , the fluctuation range is 6.9990K - 7.0030K , and the settling time is about 650 seconds . The stability time and the temperature control stability are in accordance with the experimental requirements .

【学位授予单位】：华中科技大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：O51;TB651

【相似文献】