Closed Cycle 1 K Refrigeration System

Abstract

A closed-cycle refrigerator provides cooling to extremely low temperatures, particularly in the range of 0.5 K to 2.0 K. A 4 K pulse-tube cryocooler cold head or G-M cryocooler cold head liquefies helium in a first cooling chamber at a pressure at approximately 1 atmosphere. Liquid helium flows from the first cooling chamber, through a Joule-Thomson valve, and into a second cooling chamber under a pressure differential created by a pump. Helium vapor extracted from the second cooling chamber by the pump is routed back to the first cooling chamber to be re-condensed. This closed-cycle design provides continuous cooling below 2 K. Cryocooler cold head cold sections have no physical contact with subsequent cooling elements, such as the first and second cooling chambers to reduce vibration transfer. In some embodiments the cryocooler cold head is connected to a vacuum chamber via a vibration damping coupler to further reduce vibration transfer.

Description

REFERENCE TO RELATED APPLICATIONS[0001]This application claims one or more inventions which were disclosed in Provisional Application No. 61 / 756211, filed Jan. 24, 2013, entitled “CLOSED CYCLE 1 K REFRIGERATION SYSTEM”. The benefit under 35 USC §119(e) of the United States provisional application is hereby claimed, and the aforementioned application is hereby incorporated herein by reference.BACKGROUND OF THE INVENTION[0002]1. Field of the Invention[0003]The invention pertains to the field of cryorefrigeration. More particularly, the invention pertains to closed cycle cryorefrigerators for temperatures below about 4.2 Kelvin.[0004]2. Description of Related Art[0005]Liquid helium has a boiling point at 1 atm (atmosphere of pressure) of 4.2 K, and is by-product of natural gas production. Helium is found in two isotopes, helium-3 (3He) and helium-4 (4He). Helium-4 is by far the most abundant isotope, and constitutes over 99.9% of the helium on Earth. As such, liquid helium makes an ide...

AI Technical Summary

Benefits of technology

The patent text describes a closed-cycle refrigerator that can cool to extremely low temperatures. The refrigerator uses a cryocooler cold head to liquefy helium, which flows through a Joule-Thomson valve and a second cooling chamber before being re-condensed. The refrigerator is designed to address economic and resource conservation challenges in the prior art. It also reduces vibrations caused by the cryocooler cold head, and decouples vibrations from low temperature devices. The refrigerator has an extra low vibration design, minimizing the transfer of vibrations to other components. The cold sections of the refrigerator are contained in a vacuum chamber or a cryostat to further reduce vibration transfer. The technical effects of this patent include continuous cooling below 2 K and minimized vibration transfer.

Problems solved by technology

Unfortunately, sources of natural gas that also contain helium are limited, and atmospheric helium migrates into space and is lost.

As helium is a limited resource, and world-wide demand has increased dramatically over several decades, the cost of this irreplaceable natural resource has also increased dramatically.

Therefore it is clear that a shortage, or worse depletion, of world helium reserves could potentially have a dramatic negative effect on the production and use of critical technologies such as magnetic resonance imaging, fiber optics and semi-conductor manufacturing, space exploration, and military rockets, for example.

In many cases, the devices to which cryocooler cold heads are to be connected for cooling purposes are extremely sensitive to vibration.

However, both Gifford-McMahon and pulse-tube type cryocooler cold heads produce vibrations which complicate their direct use in such applications.

This mode of operation requires costly periodic refills of the system's liquid helium.

While regenerative refrigerators, such as GM and pulse tube cryocoolers, have been developed to reach low temperatures, in the range of 4 K or less, with helium-4, they are not able to produce temperatures below the helium-4 Lambda line near approximately 2.1 K.

Images