Wide-neck GRP-Cryostat - Glass fibre reinforced plastic (GRP) liquid-helium-cryostat with wide neck

The inner container of the wide-neck GRP cryostat has a volume of about 9.3l.

The evaporation rate of the cryostat without any inserts is about 0.83%/h. That means that a dewar fully filled with liquid helium remains cold (4.2 K) for at least 120 hours, i.e. about 5 days.

The cryostat is manufactured with non-magnetic materials exclusively, mainly from glass fibre reinforced plastic. The vacuum isolation space of the “cold” cryostat should typically keep the vacuum for several months, i.e. the material of the inner container, especially the neck, must be helium tight. Tightness tests are performed according to our QM-specifications

Purpose of a cryostat

Containers for cryogenic liquids are called "cryostats" or "dewars", whereby the expressions cryostat and dewar are synonyms. Liquid helium Cryostats (boiling point: 4.2 K = -269°C = -452°F; @ 101.3 kPa) are commonly used to contain this cryogenic liquid for low-temperature superconductivity. They are developed for highly sensitive electric or magnetic measurements [1]. GRP is proven to be an optimal material for dewars used for low noise magnetic measurements because of its physical strength, low paramagnetic impurity content as well as sufficient vacuum properties. This is necessary, for example, for geophysical investigations, biomagnetism or physics basic research. The white noise level of our standard cryostat is lower than 3fT/Hz^1/2. Lower noise values can be achieved on request.

Years of development and experience have enabled Supracon AG to manufacture the cryostat from epoxy enforced materials such as GRP. These GRP-cryostats have proven themselves in various applications of different company device systems (www.supracon.com) under sometimes rough environmental conditions.

Super isolation and radiation shields

Vapor-cooled radiation shields and specific super insulation are essential to liquid helium cryostats. Super isolation and radiation shields are mounted on the inner container. Two radiation shields are thermally connected to the neck.

Super isolation is realized by multiple layers of mylar foil (thin plastic foil with an evaporation aluminium film on one side). Several layers of super isolation are placed between the inner and the outer container as well as between the radiation shields.

Specifications of the wide-neck cryostat

Geometrical data:

Height: 576 mm

Diameter: 261 mm

Neck diameter: 155 mm

Neck length: 206 mm

Helium reservoir: 9.3 l

Thermal performance data of the cryostat after standard refilling process:

Evaporation rate of the cryostat itself: about 0.83 %/h.

Boil-off rate: about 1.9 l/d

Holding time of a cold (4.2 K) cryostat: about 120 hours (about 5 days).

References

[1] P. Seidel, Applied Superconductivity, Handbook on Devices and Applications, Vol. 2, Weinheim, Wiley-VCH, 2015.