Thesis presented March 13, 2024

Abstract:
The design and availability of a miniature cooler to achieve temperatures below 2 Kelvin (-271°C) would be a significant advancement in facilitating the use of cryogenics, especially outside specialized laboratories. Currently, the most common coolers are limited to around 3 Kelvin and require substantial electrical power, typically several kilowatts. Additionally, they generate significant noise and involve a large size. Our goal is to reach lower temperatures while creating a miniature cooler. To achieve this, the project leverages the coupling of a 2 Kelvin Joule-Thomson cooler with a high-frequency pulse tube as a pre-cooler. The development of the high-frequency pulse tube is the core focus of this thesis.This system will operate in a configuration using two cascaded cold fingers, known as an intercepted pulse tube. This allows for achieving low temperatures, up to 15 Kelvin (-258°C) in this case. This configuration has been developed in the aerospace field. For generalization to laboratory cryostats, resizing work to operate with commercial pressure oscillators was necessary.The chosen approach to optimize the intercepted pulse tube is primarily experimental, relying on a phenomenological analysis of thermodynamic processes and numerical modeling. Emphasis has been placed on evaluating heat losses at the intermediate stage (intercept). A pre-industrial version of the pulse tube has been developed and tested. Its performance reaches up to 430 mW of cooling power from a mechanical power of 100 W.As an example of applications, in research laboratories, this system will enable the detection of single photons based on superconducting nanowire detectors or research on quantum technologies.

Keywords:
Engineering sciences, Cryogenics, Energetics, Process engineering, Mechanics

On-line thesis.​