Development of a sub-mK Continuous Nuclear Demagnetization Refrigerator

TL;DR

This paper reports the development and simulation of a two-stage continuous nuclear demagnetization refrigerator capable of reaching sub-millikelvin temperatures with minimal heat load, advancing ultra-low temperature cooling technology.

Contribution

It introduces a novel two-stage continuous nuclear demagnetization refrigerator design and provides detailed thermal modeling and simulations of its performance.

Findings

Achieves 1 mK temperature under 20 nW heat load with careful thermal management.

Demonstrates the importance of thermal links and heat switches in cooling performance.

Provides a detailed thermal model including sources of heating and material properties.

Abstract

We present the development of a two-stage PrNi$_5$ continuous demagnetization refrigerator at the Institut N\'{e}el/CNRS and numerical simulations of its performance. The thermal model used in the simulations is discussed in detail including the likely sources of heating. We demonstrate the effects of the critical thermal links including superconducting heat switches as well as the heat conductivity of the PrNi$_5$, accounting for the dependence of cooling power on the PrNi$_5$ rod diameter. Our simulations show that if extreme care is taken to minimize the thermal resistance between the nuclear stages, a sample temperature of 1~mK can be maintained under a 20~nW heat load.