Développement d'un réfrigérateur à dilution prérefroidi par un tube à gaz pulsé

Abstract : The dilution refrigerators operation implies liquid consumption. These refrigerators are not stand-alone, so their use becomes constraining and expensive for laboratories which do not have liquefaction facilities. At the end of the 90's, the performance of commercial two-stage pulse tubes were good enough that the idea to use them to replace traditional helium baths emerged. Laboratory prototypes were developed. One of them was marketed by Air Liquide in collaboration with the CRTBT. In the framework of this thesis carried out at the CRTBT and co-funded by Air Liquide, a dilution refrigerator coupled to a pulse tube was studied. The objective is to produce a commercial apparatus offering equivalent performances to traditional refrigerators in terms of experimental volume and cooling power. In a first step we focused on the cryostat study. In particular the absence of cryogenic fluids enabling the homogeneous thermalisation of the various entities, as well as the limited cooling power of the pulse tube and the induced vibrations were investigated. A cryostat offering an experimental volume of 750mm length with a diameter of 200 mm was then designed and manufactured. The precooling time between 300 K and 4,2 K is 12 hours. In a second step, we studied the integration of the dilution refrigerator into the cryostat. The 3he inlet precooling between 300 K to 4,2 K was done by developing a specific system allowing to optimize the pulse tube resources. This work led to a CNRS/Air Liquide patent. The precooling between 4,2 K and the temperature of the still required an important work on the Joule-Thomson exchangers. We reached temperatures lower than 10 mK and obtained 3he circulation flows ranging from 90 to 200 micromoles/s with a condensation time of about 2 hours for a refrigerator with two step exchangers.
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Thomas Prouvé. Développement d'un réfrigérateur à dilution prérefroidi par un tube à gaz pulsé. Instrumentations et Détecteurs [physics.ins-det]. Université Joseph-Fourier - Grenoble I, 2007. Français. ⟨tel-00201891⟩

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