Dry dilution refrigerator

Dry dilution refrigerator
A dry dilution system


A dry (or cryogen-free) dilution refrigerator is a type of dilution refrigerator that does not require the use of any external cryogens, in particular liquid helium, to operate.

In the traditional design of a dilution refrigerator (Figure 1a) a liquid helium bath is used. It mainly serves the following purposes:

  • It initially precools the unit from room temperature to 4.2 K.
  • It acts as a thermal radiation shield.
  • It cools the returning incoming 3He and helps to condense it.

In a dry dilution refrigerator a cryocooler is integrated in the design of the refrigerator in order to replace the liquid helium bath (see Figure 1 below). The first experimental machines were built in the 1990s,[1] when (commercial) cryocoolers became available, capable of reaching a temperature lower than that of liquid helium and having sufficient cooling power (on the order of 1 watt at 4.2 K). At present the most commonly used cryocooler is a pulse tube cooler.


Different designs


The dry dilution refrigerator design shown in Figure 1b is the easiest to realize from an engineering point of view, but not the easiest in operation. The design incorporates an inner vacuum can, which is used to initially precool the machine from room temperature down to the base temperature of the pulse tube cooler (using heat-exchange gas). However, it implies that every time the refrigerator is cooled down, a vacuum seal that holds at cryogenic temperatures needs to be made. It also implies complications (low temperature vacuum feed-through) in the experimental wiring.

A design as shown in Figure 1c is possible, but technically more demanding to realize. It requires the use of heat switches, which are necessary for precooling. The heat switches and thermal radiation shields are not shown in the figure. This type of refrigerator is in the SCUBA-2 sub-millimetre camera on the James Clerk Maxwell Telescope.

References

  1. ^ K. Uhlig and W. Hehn, Cryogenics 37, 279 (1997).

External links


Wikimedia Foundation. 2010.

Игры ⚽ Поможем сделать НИР

Look at other dictionaries:

  • Dilution refrigerator — Gas control system for a helium dilution refrigerator A dilution refrigerator is a cryogenic device first proposed by Heinz London. Its refrigeration process uses a mixture of two isotopes of helium: helium 3 and helium 4. When cooled below… …   Wikipedia

  • Pulse tube refrigerator — The Pulse tube cryocooler is a developing technology that emerged largely in the early 1980 s with a series of other innovations in the broader field of Thermoacoustics. In contrast with other cryocoolers (eg Stirling cryocooler and Gifford… …   Wikipedia

  • Cryostat — NASA s WISE infrared instrument is kept cold by a cryostat. The cryostat can be seen at the top of the spacecraft. A cryostat (from cryo meaning cold and stat meaning stationary) is a device used to maintain cold cryogenic temperatures. Low… …   Wikipedia

  • Pulsröhrenkühler — Ein Pulsröhrenkühler oder Pulsrohrkühler (auch Pulse Tube Kühler) ist eine auf dem Prinzip des Stirlingmotors basierende Kältemaschine. Der Vorteil gegenüber dem Stirlingmotor liegt darin, dass in der Nähe des kalten Wärmetauschpunktes keine… …   Deutsch Wikipedia

  • Evaporative cooler — An evaporative cooler, photographed in Rocky Ford, Colorado, used in the drier parts of the American West to provide economical cooling …   Wikipedia

  • United States — a republic in the N Western Hemisphere comprising 48 conterminous states, the District of Columbia, and Alaska in North America, and Hawaii in the N Pacific. 267,954,767; conterminous United States, 3,022,387 sq. mi. (7,827,982 sq. km); with… …   Universalium

  • Haloalkane — The haloalkanes (also known as halogenoalkanes or alkyl halides) are a group of chemical compounds, consisting of alkanes, such as methane or ethane, with one or more halogens linked, such as chlorine or fluorine, making them a type of organic… …   Wikipedia

  • Glossary of environmental science — This is a glossary of environmental science.Environmental science is the study of interactions among physical, chemical, and biological components of the environment. Environmental science provides an integrated, quantitative, and… …   Wikipedia

  • Activated carbon — Activated carbon, also called activated charcoal, activated coal or carbo activatus, is a form of carbon that has been processed to make it extremely porous and thus to have a very large surface area available for adsorption or chemical reactions …   Wikipedia

Share the article and excerpts

Direct link
… Do a right-click on the link above
and select “Copy Link”