Cryogenic microcooling : a micromachined cold stage operating with a sorption compressor in a vapor compression cycle

Abstract

Cryocoolers are refrigerators capable of reaching temperatures below roughly 120 kelvin. Such coolers are used for cooling of, for instance, superconducting electronics and magnets, (infrared) detectors, and cryopumps. Low-temperature applications requiring very little cooling power, such as a single chip with a low noise amplifier or a superconducting magnetometer, would benefit from very small closed-cycle cryocoolers. Such coolers do not yet exist. This thesis is the result of a research project to investigate opportunities for such microcoolers. The project required a high degree of pioneering because the field of subjects and possibilities is vast and largely unexplored. As a result, the contents of this thesis is very divergent and cover various areas of science, such as (micro)mechanics, thermodynamics, fluid mechanics, heat transfer and material science. This divergence occurs especially in chapters 2 and 3, in which a number of cooling cycles are discussed, as well as opportunities for miniaturization of these coolers. The remainder of the thesis describes the development of miniature components for a sorption cooler. This cooling system was chosen because it is suitable to be applied on a small scale