Hybrid cryocooler with multiple passive stages

Abstract

A multi-stage cryocooler has three or more stages, including an active first stage and passive second and third stages. The active stage may include a Stirling expander, and the passive second and third stages may be pulse tube coolers. The cryocooler may provide cooling at three different temperatures. The coldest cooling temperature may be at or below 10 K, and may be at or below 5 K. The system may provide cooling at such low temperatures while still operating at a relatively high frequency, for example, at a frequency of at least about 20 Hertz.

Description

BACKGROUND OF THE INVENTION [0001] 1. Technical Field of the Invention [0002] This invention is in the field of cryocoolers, and more particularly in the field of regenerative cryocoolers. [0003] 2. Background of the Related Art [0004] Multi-stage cryocoolers are of fundamental interest for many applications in which cryogenic cooling is required. For example, some applications require the simultaneous cooling of two or more objects to cryogenic, but different, temperatures. In the case of a long wave infrared sensor, for instance, the focal plane assembly may require an operating temperature of around 40 K, while the optics may need to be maintained at a different temperature, such as about 100 K. One approach for such situations is to use a single-stage cooler and extract all of the refrigeration at the coldest temperature. However, this is thermodynamically inefficient. Another approach is to use two single-stage cryocoolers with one each at the two temperature reservoirs. This a...

AI Technical Summary

Benefits of technology

[0008] According to an aspect of the invention, a cryocooler has three or more stages, at least one of which is an active stage, defined as a stage driven by a moving piston, and at least another of which is a passive stage.

Problems solved by technology

However, this is thermodynamically inefficient.

This approach has the disadvantage of being expensive and large in size.

This has caused difficulties, particularly in space flight applications, where the cooling system must be able to withstand loads and random vibrations generated during launch.

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