Design Evaluation of Serial and Parallel sub-mK Continuous Nuclear Demagnetization Refrigerators

TL;DR

This paper evaluates two design configurations of a two-stage continuous nuclear demagnetization refrigerator, focusing on cooling power at sub-mK temperatures and how design choices affect performance through numerical simulations.

Contribution

It provides a comparative analysis of serial and parallel configurations of the refrigerator, highlighting the impact of thermal link quality on performance.

Findings

Parallel configuration offers higher cooling power than serial for same thermal link resistance.

Performance improves with better thermal links in both configurations.

Simulations align with previous findings on the importance of thermal link quality.

Abstract

We present the evaluation of two different design configurations of a two-stage PrNi$_5$ continuous nuclear demagnetization refrigerator. Serial and parallel configurations of the two stages are considered, with emphasis on the attainable cooling power at sub-mK temperatures and the impact of the design choices on the operation of the refrigerator. Numerical simulations of heat transfer in the setup are used to evaluate the performance of the refrigerator as well as the technological requirements for the essential thermal links. In accord with similar findings for adiabatic demagnetization refrigerators [Shirron, \emph{Cryogenics} \textbf{62}, 2014], our simulations show that the performance of both configurations improves as the thermal links improve, and that the parallel configuration yields a higher cooling power than the series design for a given thermal link resistance and sample temperature.