Cryostat

(redirected from cryostats)
Also found in: Dictionary, Thesaurus, Medical.

cryostat

[′krī·ə‚stat]
(engineering)
An apparatus used to provide low-temperature environments in which operations may be carried out under controlled conditions.

Cryostat

 

a thermostat in which the working unit or the object under study is maintained at temperatures below 120°K (cryogenic temperatures) by an external cooling source. The coolant is usually a liquefied or solidified gas with low liquefaction and freezing temperatures (such as nitrogen, hydrogen, helium). The temperature of an object placed in the cryostat is controlled by changing the vapor pressure over the coolant in the cryostat or by heating the vapors of the coolant. Cryostats are classified according to the type of cooling agent used (nitrogen, helium, and hydrogen), the type of material used (glass, metal, or plastic), and the function (for electronic, optical, and other research; superconducting magnets; and radiation detectors).

Cryostats of all types require shielding of their working chambers from the influx of heat from the surrounding medium. The thermal insulation requirements for the working modules of cryostats increase with decreasing boiling point and heat of vaporization of the coolant used. Cryostats filled with liquid nitrogen or oxygen frequently use high-vacuum thermal insulation, similar to that used in the widely known Dewar flasks and domestic vacuum bottles. However, ordinary high-vacuum insulation is inadequate for helium cryostats. Therefore, to decrease the flux of radiant energy from the exterior walls of the cryostat, it is necessary to reduce their temperature; this is done through cooling of the walls by an auxiliary coolant (for example, liquid nitrogen) or by installation in the thermal insulation space of screens that reflect radiation.

Glass cryostats are widely used in laboratory practice. They are simple to fabricate and are transparent, which makes possible direct observation of experiments. A general-purpose glass helium cryostat usually consists of two Dewar flasks, one inside the other. The inner flask is filled with liquid helium, and the outer flask is filled with liquid nitrogen. Low mechanical strength is a disadvantage of glass cryostats.

Metal cryostats are more reliable in use; the most versatile cryostats of this type use liquid helium as the basic coolant. In a metal helium cryostat with additional liquid-nitrogen cooling, the helium container of the cryostat is surrounded on all sides by a copper screen. High vacuum, which is maintained during operation by an adsorbent, is generated in the space between the helium container and the jacket. A bellows is built into the cryostat to compensate for the thermal stresses arising between the interior cells and the enclosure. Cryostats are constructed from copper, stainless steel, or aluminum alloys. The surfaces of the cryostat cells are polished on the vacuum side to reflect heat.

Metal cryostats designed for optical studies contain windows, as well as rotation devices, which may be used for changing the position of the sample. Cooling of the screens in helium and hydrogen cryostats is performed by vapors of the main coolant rather than liquid nitrogen. Cryostats are widely used in cryogenic engineering.

References in periodicals archive ?
For GUSTO, Ball will redesign the STO cryostat to enable the much longer mission duration and maintain the detectors at their operating temperature of 4.
We store up to six patients inside each Cryostat and they are suspended upside down on boards, wrapped in everyday normal sleeping bags.
North America held the major share of the overall cryostats market in 2015.
Each cryostat is composed of different parts, stainless steel, aluminum, Invar, copper, titanium and composite materials (type G11).
The subject of the public tender is the supply, installation, operator training qualified personnel and providing warranty and post-warranty service guaranteed two helium cryostat with closed cycle for mE[micro]ssbauer spectroscopy.
Microscope cryostats are divided into two main groups, although the division is far from rigid.
Lot 2 for the purchase of a set of two helium flow cryostats mounted on a frame and equipped with accessories specified in the special technical provisions of the contract.
In an advisory issued today, Pirelli indicated that the cable cryostats, which use a vacuum to limit the amount of heat entering each cable, are able to achieve only partial vacuum.
This cryogenic plant can produce liquid helium needed to cool and continuously feed a seven cryostats of superconducting magnets.
Cryenco's products include cryogenic road transport trailers for oxygen, nitrogen, argon, and LNG; proprietary TVAC(R) intermodel tank containers; and MRI cryostats.