Nonmagnetic low-vibration coaxial impulse pipe refrigerating machine

Abstract

The invention relates to a non-magnetic low vibration coaxial pulse tube refrigerating machine wherein the pulse tube and the cold accumulation device are in coaxial arrangement, between which cold accumulation stuffing is filled, an arched flow diverter is arranged on an extending section and the end portion, closely spaced vertical through-holes are arranged on the arched portion, vertical grooves are arranged evenly circular ring external wall, the cover type cold end heat exchanger covers the groove and packs by bonding, the horizontal split cold platform supported by the support rod and fixed on the hot end flange vertically are arranged on the cold end heat exchanger, the cold platform and cold end heat exchanger are connected by flexible heat guide band, the coupling channel under the throttle holes are connected to phase modulation capillary.

Description

field of invention [0001] The invention belongs to the technical field of refrigeration and low temperature, and in particular relates to a non-magnetic and low-vibration coaxial pulse tube refrigerator. Background technique [0002] The wide application of superconducting devices based on superconducting quantum interferometers (SQUID) depends on the development of low-temperature systems. In many occasions such as space or underwater submarines, it is the lack of suitable low-temperature systems that limits the use of SQUID devices. Using mechanical refrigeration methods instead of directly immersing SQUIDs in a Dewar containing cryogenic liquids has been a challenge in the field of cryogenics for nearly three decades. Superconducting devices based on superconducting quantum interferometers have very strict requirements on the environment. For example, the sensitivity of SQUID in superconducting geomagnetism is about 10 times that of the earth...

AI Technical Summary

Problems solved by technology

However, there are still two major defects in the existing pulse tube refrigerator: one, for the Stirling refrigerator, its vibration has been greatly reduced, but the system itself, especially the cold head coupled with the SQUID device, still has obvious residual Vibration, the interference caused by this vibration still far exceeds the measurement accuracy of the SQUID device, and even makes the measurement of the SQUID device meaningless; 2. The components of the refrigerator are made of materials or Made of metal materials, the magnetic interference signal directly attached by the magnetic parts in the refrigerator in the working environment, and the induced eddy current generated by the movement of the metal parts in the refrigerator in the working environment seriously interfere with the operation of the SQUID device

Taking this typical coaxial pulse tube refrigerator as an example, since the cold head does not take any measures, it can be detected that the cold head expands and contracts with the pulse tube under the condition of a typical inflation pressure of 1.8Mpa and a typical operating frequency of 50Hz. The Z-axis has an elastic expansion and contraction of 10-20 μm. In this way, when the change rate of the local geomagnetic field strength along the Z-axis is 250nT / m, the magnetic field change caused by this expansion and contraction is about 2.5-5.0pT. The impact of this magnetic field change on SQUID is huge; its main components are made of materials with large remanence or metal materials, such as pulse tubes and regenerator tube walls made of thin-walled stainless steel tubes or titanium alloy tubes , The regenerator packing is composed of fine wire mesh, small metal balls or particles, the hot end flange and vacuum cover are made of stainless steel, each deflector is made of stainless steel or copper, and the cold and hot end heat exchangers are made of pure copper. As a result, the magnetic interference signal attached to the material and the induced eddy current are far beyond the upper limit that the SQUID device can tolerate; the connection between the components of its refrigerator is threaded and welded, and the welding brings more Large magnetic impurities also affect the measurement of SQUID; the compressor and the refrigerator body are rigidly connected, and the rigid connection directly transmits the vibration of the compressor itself to the refrigerator. This vibration interference is sometimes serious enough to make the operation of the SQUID device It cannot be done; it does not have a deflector at the cold end of the pulse tube, or only uses a densely perforated flat plate, which cannot ensure the stability and uniformity of the airflow within the 180-degree turning range, thereby inducing the vibration of the cold-end heat exchanger and causing Affect cooling efficiency

In view of the above shortcomings, the existing coaxial pulse tube refrigerator represented by this type of pulse tube refrigerator cannot directly serve the operation of SQUID devices.

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