PROGRAM

Tuesday 2 November; Anthony Matthews Cryogen free dilution refrigerators''

Date:

 

Time: 13:30 pm

Room: Zaal E (F005)

Abstract:

This seminar will outline the basic principles behind “dry” dilution fridge technology and describe how Oxford Instruments have addressed the technical challenges in designing cryogen free systems. The latest developments will be presented, along with a vision for the future direction of ultra low temperature environment systems.

Longer abstract:

Cryogen-free dilution refrigerators have been the subject of many research projects recently; this has mainly been driven by the end-user community wanting to move towards “dry” technology. Cryogen-free systems have some advantages from a safety and convenience point of view as they do not use liquid cryogens. They also enable institutes without a history of low-temperature research, and the associated infrastructure: liquefiers; storage dewars; recovery systems etc., to embark on projects requiring access to the milli-Kelvin temperature range without investing in this ancillary equipment.

However, the huge additional benefits that these systems may offer to the experimenter are often overlooked. As no liquid helium bath is required, the geometry of the fridge can be very different from a traditional “wet” system. The fridge can be designed to provide much more experimental access for services and wiring and ample space to heat sink these services effectively.

Oxford Instruments have also developed a pre-cooling technique that removes the need for an inner vacuum can, meaning that only room-temperature o-rings need be demounted to access the entire system. In addition to the improved convenience, this also removes the need for cryogenic feed-throughs for experimental wiring. This makes the experimental set-up easier, more reliable and easier to heat-sink, allowing unprecedented wiring capability to the sample.

Oxford Instruments have also demonstrated the integration of cryogen-free superconducting magnets (of up to 12 T) and dilution refrigerators into one system requiring only a single pulse tube cooler. The effective thermal linking of the magnet current leads and the lack of an IVC also means that the mixing chamber plate can be controlled at higher temperatures than normally attainable in a traditional wet system, thus providing a unique experimental B-T environment.

Oxford Instruments have also developed rapid sample exchange mechanisms which enable the user to load a sample in less than 30 mins and automated fridge cooldown routines which then recover base temperature in around 6 hours. This seminar will outline the basic principles behind “dry” dilution fridge technology and describe how Oxford Instruments have addressed the technical challenges in designing cryogen free systems. The latest developments will be presented, along with a vision for the future direction of ultra low temperature environment systems.

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