Enabling the next generation of millikelvin cryocooler.

Lead Research Organisation: University College London
Department Name: Mullard Space Science Laboratory


This grant application seeks to advance our current state-of-the-art sub-Kelvin millikelvin cryocooler.
Cryogenics is an enabling technology and sub-Kelvin cooling is required for many advanced technologies under development, e.g. Imagers using single photon detectors and quantum technologies. Applications of these technologies range from medical and security to computing and communications. Historically, cryogenic systems have been large (sometimes room-sized) and cumbersome and require specialist knowledge to operate, which is prohibitive to the development of these new and advanced technologies. Our focus is to remove such limitations and open up the field of ultra-low temperatures to non-Cryogenic specialists in both academia and industry. Through EPSRC funding, the Cryogenics group at MSSL/UCL have built the first fully autonomous, cryogen-free, easy-to-use, low mass (< 5 kg), compact and continuous millikelvin cryocooler, which is capable of providing continuous cooling at any temperature between 0.85 and 4 Kelvin at the press of a button - no specialist knowledge is required to operate it. We propose to build on this success and perform targeted component level research and development to address fundamental heat transfer processes through a combination of computer modelling, experimental investigation, materials development and engineering as well as develop bespoke electronics hardware. Our aim is that this research will benefit not only our research, but a wide-range of other disciplines. This research will significantly improve and advance our millikelvin cryocooler, enabling a base temperature of 0.3 Kelvin to be obtained when operated from 4 Kelvin and below 0.1 Kelvin to be obtained when pre-cooled to below 2 Kelvin, which is required for the technologies mentioned above (2 Kelvin can be provided by either a 2nd millikelvin cryocooler or a commercially available sub-2 Kelvin cooler). Such development will keep the UK at the forefront of millikelvin cryogenic cooling, whilst enabling the wider application and commercialisation of new cryogenic technologies both in the UK and internationally.

Planned Impact

Millikelvin cryogenics is an enabling technology, in particular for ultra-low temperature detectors and devices which have a range of applications from medical imaging, defence and security, astronomy, quantum communications, quantum computing as well as basic research. In order to commercialise and maximise the impact of these emerging and highly desirable technologies, the cooling systems need to be small, lightweight and straightforward to operate - to be attractive to the user (and therefore commercially viable), the cooling system needs to be 'invisible' to the user (a black box), user-friendly and not requiring any specialist cryogenic knowledge. Our application to enable the next generation of millikelvin cryocooler will be a significant step in being able to meet these requirements, ensuring that the UK stays at the forefront of millikelvin cooling and ultra-low temperature instrumentation.
The proposed project is primarily focussed on component-level research and development by addressing fundamental physics processes and developing hardware that is not available commercially. The work builds upon decades of innovative cooler development at MSSL/UCL. The main impact during the project lifetime is the dissemination of the research to the wider scientific community, the development of bespoke superconducting magnet power supplies and the demonstration of the next generation of millikelvin cryocooler operating at 300 mK from a 4 K bath temperature. Dissemination of the research and publicising of the technological developments, will be accomplished by the publication of three research papers in international journals and attendance at an international conference. In addition to being of interest to the cryogenic cooler community we expect our research to be applicable to a wide-range of disciplines due to the fundamental physics and materials development nature of the research. We will also work closely with UK industry during the proposed project in order to develop the bespoke components we need. This will require not-yet-developed techniques and processes in order to meet our requirements. By undertaking this research, we are supporting UK industry in furthering their capabilities.
Following the completion of the proposed work, we will:
1) Apply the research to the 2-stage millikelvin cryocooler (mKCC) being built for the Quantum Microwave Sensor at the University of Sussex. This will be the first real-world application of the mKCC technology, and this 2-stage cooler will be the first demonstration of a 2-stage mKCC, which will be capable of providing cooling below 100 mK.
2) Use the developed next generation mKCC to set up a unique research facility based at MSSL. The goal of the facility will be to expand the use of millikelvin cryogenics for both fundamental research (such as materials characteristics and development) and further enable the development of novel applications i.e. quantum and detector devices.
3) Take steps to transfer the bespoke magnet power supply capability to UK industry.
4) Take steps to transfer the mKCC technology capability to UK industry. There is a strong UK cryogenics industrial community (e.g. ICE Oxford, Scientific Magnetics, Oxford Instruments, Cryogenics Ltd.) and our mKCC would enhance their cooler portfolio. We believe commercialising the mKCC would maximise its impact for both science research and enabling the commercialisation of ultra-low temperature applications.


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Description The grant objectives are related to improving the performance of a milli Kelvin Cryocooler. Some specific issues have been addressed which would be of interest to those working in this field. These relate to thermal boundaries (geometries and materials), eddy current heating (dependence on magnetic field ramp time, heat switch geometry, material)
Exploitation Route These findings will be published in an appropriate journal. Cooler developers, including those in industry, will find the information helpful in their designs. Moreover, the results are expected to lead to a high performance cooler demonstration which will find application in a variety of fields. UCL will explore commercialisation of this cooler.
Sectors Aerospace, Defence and Marine,Other

Title Eddy Current Heating models 
Description Eddy Current heating is an important factor in milliKelvin Cryocoolers. Computer models have been produced that predict this phenomina for a variety of physical geometries 
Type Of Material Improvements to research infrastructure 
Year Produced 2021 
Provided To Others? No  
Impact Research is ongoing but the model has directly impacted the design of future millikelvin cryocoolers 
Title Heat strap design 
Description Thermal heat straps are essential to millikelvin cryocoolers. Eddy current heating in heat straps can be a serious issue. Heat straps with reduced eddy current heating have been designed. 
Type Of Material Improvements to research infrastructure 
Year Produced 2021 
Provided To Others? No  
Impact Research is in progress but the design of a future millikelvin cooler has been influenced by this work.