An introduction to cryogenics
An introduction to cryogenics
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低温学简介
DOI：
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发表时间：
2007
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通讯作者：
A. Woodcraft
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作者：
A. Woodcraft
这些笔记旨在对低温的方法(偶尔还有为什么)提供一些基本的介绍。低温不是一个很好的定义；在这里，我把它理解为指在77K及以下工作的系统，重点是工作在4.2K以下和1K以上的系统。当然，前两个温度分别是氮和氦的沸点。低温实验或系统通常以获得并保持低温的需要为主导，设计的其他元素从属于此。一般来说，需要在低温下操作，即使是一个原本很简单的实验也会变得复杂，而且你需要去的越冷，生活通常就会变得越困难。由于将东西冷却非常耗时，试验新技术的能力受到一定程度的限制，大多数低温实验室坚持使用一套经过验证和信任的方法。通常不同的实验室有不同的结论，而且在最有趣的情况下是相互矛盾的。首先，有几个基本的定义。在这些笔记中，我将按照这里定义的方式使用以下词语(这些并不是唯一的定义)--低温恒温器：低温实验所用的系统--杜瓦：用于储存和(可能)运输液体冷冻剂的东西氦有两种同位素：从油井和气井中获得的常见氦-4(氦)(它以阿尔法粒子形式开始生命)以及更奇异的氦-3(氦)，它在自然界中不存在，但由氚的衰变产生。有几本书你可以在这些笔记上展开论述，在几年的疏忽之后，旧书正在以新版本重印，新书也出现了。下面列出了我最常参考的几本书；还有其他一些书也很值得一读。-Ekin(参考文献)[1])；这是一本新书，在低温的许多方面提供了许多有用的、详细的、切合实际的建议，尽管它通常限于1K以上的温度，并强调对超导体进行测量(您可能认为这是一件好事，也可能不认为是一件好事)。-White and Meeson(参考文献)[2])也是非常值得一读的，而且是最新的。-波贝尔(参考文献)[3])是另一本标准教科书，最近又出了一个新版本。-Richardson and Smith(参考文献)[4])是康奈尔大学低温组的研讨会集合，虽然有些地方有些过时，但也提供了许多动手实践的建议。-Wigley(参考文献)[5])提供了有关材料机械性能的有用信息。
These notes aim to give a somewhat basic introduction to the hows (and occasionally whys) of cryogenics. Cryogenics is not a very well defined term; here I have taken it to mean systems that operate at temperatures of 77 K and below, with the emphasis on systems operating below 4.2 K and above 1 K. The first two temperatures are, of course, the boiling points of nitrogen and helium respectively. A cryogenic experiment or system is normally dominated by the need to get something cold and keep it cold, with other elements of the design subservient to that. Generally, the need to operate at cryogenic temperatures makes even an otherwise simple experiment complicated, and the colder you need to go, the harder life generally gets. Since it is so time consuming to get things cold, the ability to experiment with new techniques is somewhat limited, and most low temperature labs cling to a set of tried-and-trusted methods. Often these differ from lab to lab, and in the most interesting cases are contradictory. First, a few basic definitions. In these notes, I shall use the following words in the way defined here (these are not the only definitions) – cryostat: the system that a low temperature experiment goes in – dewar: something for storing and (possibly) transporting liquid cryogens Helium comes in two isotopes; the common helium-4 (He), which is obtained from oil and gas wells (it starts life as alpha particles) and the much more exotic helium-3 (He) which does not occur in nature, but is produced by the decay of tritium. There are several books to which you can turn to expand on these notes, and after some years of neglect, old books are being reprinted in new editions, and new books appearing. The following lists the ones that I refer to the most; there are other books which are also well worth reading. – Ekin (Ref. [1]); this is a new book, and gives lots of useful, detailed, down-to-earth advice on many aspects of cryogenics, though it is generally limited to temperatures above 1 K, and has an emphasis on making measurements on superconductors (you may or may not think this is a good thing). – White and Meeson (Ref. [2]) is also a very worthwhile read, and is up to date. – Pobell (Ref. [3]) is another standard textbook, and a new edition has recently appeared. – Richardson and Smith (Ref. [4]) is a collection of seminars from the Low Temperature Group at Cornell University, and although somewhat out of date in places gives a lot of hands-on advice. – Wigley (Ref. [5]) gives useful information on mechanical properties of materials.