A bulk MgB2 magnet demonstrator for biomedical applications
Lead Research Organisation:
Science and Technology Facilities Council
Department Name: Technology
Abstract
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| Description | High magnetic fields are used in many areas of our lives, such as MRI body scanners, and in the magnetic bearings utilised in magnetic levitation (Maglev) trains and flywheel energy storage systems. There is also growing interest in the use of magnetic fields for novel therapeutic applications including magnetically targeted drug delivery (a particular focus of this project), magnetic cell separation and controlled local heating for treating cancerous tumours. Magnesium Diboride (MgB2) bulk superconductors offer the potential to generate larger magnetic fields than can be achieved in conventional permanent magnets, along with the flexibility to do so in a wider range of geometries than is possible with electromagnets. Furthermore, their superconducting properties can be accessed at a temperatures up to 39 K (-234°C) - well above many superconducting materials used in existing applications - and the manufacturing requirements for the bulks are much less stringent than other high temperature superconductors. However, while MgB2's operating temperature is more amenable than many other superconducting materials, it still requires a cryogenic cooling system that is compact and easily deployable in environments such as hospitals. This was the key challenge addressed in this part of the grant. A compact cryogenic cooling system has been designed and built to cool MgB2 bulks (pellets) up to a diameter of 50 mm. It is based around a Joule-Thomson (JT) cooler using neon as the working fluid. Neon is well suited to this application because it forms liquid at 27 K under atmospheric pressure, meaning that the MgB2 bulk can be cooled by a liquid bath, giving good temperature stability, at well below the temperature at which it super-conducts. Nevertheless, a small JT cooler of this type has limited cooling power and therefore the MgB2 must be very effectively insulated from its surroundings - especially challenging when it is important to maintain access as close as possible to the face of the sample, where the magnetic field gradient is highest. This grant has allowed the development of a small 'cryostat' that provides effective insulation of the MgB2¬ and limits the heat load on the cooling system, while still providing external access within 9 mm of the sample surface. An initially unexpected aspect of using neon as the working gas was that the system is highly sensitive to impurities. All JT coolers are susceptible to problems from impurities because the cooling is achieved by expanding the working gas through a small restriction, which can easily block if contaminants freeze out there. However, it was discovered that this could be a particular issue for neon JT coolers because common impurities, such as nitrogen, cannot be trapped (i.e. frozen out) in higher temperature parts of the cooler, due to the combinations of temperature and pressure at which they freeze. A method for purifying neon during the process of filling the cooler was developed, utilising temperature controlled cryogenic cooling of the gas, and successfully demonstrated on this project. This development has gone on to inform and enable the development of neon JT cooling systems for space missions, which are closely related to the type of system developed on this grant. |
| Exploitation Route | While the design of the cryogenic system still requires some further improvement, many aspects could be applied in the design of similar compact cryogenic systems for other emerging technologies, such as the type of single photon detectors that will be important in establishing quantum secure communications networks. The lessons learnt on this project are already being employed to enable the development of neon JT cooling systems for future space missions. One such mission being developed by the European Space Agency, Ariel, will enhance our understanding of planets around other stars and help to answer fundamental questions about their properties and origins. |
| Sectors | Aerospace, Defence and Marine,Healthcare |
| Description | The results of testing on a neon JT cooler breadboard, conducted under this grant, have informed the design of a cooler of this type for future space missions. The space version of the cooler will be flown on the European Space Agency Ariel (Atmospheric Remote sensing Infrared Exoplanet Large survey) space mission, due to launch in 2028. The measurements enabled by this technology will revolutionize our understanding of exoplanets, their formation and atmospheres. The research has been invaluable in allowing the UK to contribute to the ARIEL mission and this will bring investment to the UK space industry. |
| First Year Of Impact | 2019 |
| Sector | Aerospace, Defence and Marine,Education |
| Impact Types | Societal,Economic |