The effect of low temperature cryocoolers on the development of low temperature superconducting magnets

Abstract

Abstract--The commercial development of reliable 4 K cryocoolers improves the future prospects for magnets made from low temperature superconductors (LTS). The hope of the developers of high temperature superconductors (HTS) has been to replace liquid helium cooled LTS magnets with HTS magnets that operate at or near liquid nitrogen temperature. There has been limited success in this endeavor, but continued problems with HTS conductors have greatly slowed progress toward this goal.The development of cryocoolers that reliably operate below 4 K will allow magnets made from LTS conductor to remain very competitive for many years to come. A key enabling technology for the use of low temperature cryocoolers on LTS magnets has been the development of HTS leads. This report describes the characteristics of LTS magnets that can be successfully melded to low-temperature cryocoolers. This report will also show when it is not appropriate to consider the use of low-temperature cryocoolers to cool magnets made with LTS conductor. A couple of specific examples of LTS magnets where cryocoolers can be used are given.

Applications of high-temperature superconductors in power technology

“…Technical progress in HTS current leads has been substantial, and this has been one of the earliest commercial successes for HTSs. HTS leads have been used in conduction-cooled magnets for MRI [74] and are being installed as replacement leads for most major accelerators that use superconducting magnets, such as the CERN LHC [75]. Current leads can also be used to reduce heat loads to HTS devices that operate at 20-30 K, e.g.…”

A low power cryocooled autonomous ultra-stable oscillator

“…The advent of reliable two-stage cryocoolers makes it possible to replace the out-dated liquid helium facilities in number of very demanding scientific applications [1,2]. In the field of Time and Frequency metrology, the most stable frequency source is based on a microwave whispering gallery mode sapphire res-5 onator cooled near 6 K [3].…”

The integration of liquid cryogen cooling and cryocoolers with superconducting electronic systems

“…The various options for cooling superconducting electronic systems include: (1) boiling liquid cryogen cooling using either liquid helium or liquid nitrogen (for some devices liquid neon may be an option, but liquid neon is expensive to use as a throw away coolant), (2) cooling with relatively small cryocoolers or (3) cooling with more conventional liquid helium or liquid nitrogen refrigerators. This paper will deal only with the first two options, because most electronics applications for superconductivity have low heat loads and they are housed in a limited space.…”

“…When one uses a cryocooler as the method for cooling the electronic device, a number of issues come into play. They are: (1) the vibration characteristics of the cryocooler and the method used to isolate the cooler from the device, (2) the temperature difference between the electronic device and the cryocooler cold head, (3) the reliability of the cryocooler and (4) the cost of purchasing and running the cryocooler. One of the approaches that have been used for connecting cryogenic devices to a cryocooler is to use a liquid cryogen interface.…”