Design and construction of a refrigerator-cooled adiabatic calorimeter for heat capacity measurement in liquid helium temperature region.

The article focuses on the design, construction, and evaluation of a low-temperature adiabatic calorimeter equipped with a Gifford–MacMahon (G–M) refrigerator for measuring the heat capacity of condensed matter between 4 and 100 K without the use of liquid helium. This calorimeter features a mechanical thermal switch for rapid mode switching and achieves measurement repeatability and accuracy within 0.8% and 1.5%, respectively, as verified by standard reference materials including copper, sapphire (α-Al₂O₃), and benzoic acid. The instrument's capability to measure heat capacity below 5 K distinguishes it from previous refrigerator-cooled calorimeters, which typically operate above 15 K. Additionally, the calorimeter was applied to study α-Fe₂O₃ nanoparticles, demonstrating its utility for novel materials. Its fully electric operation and elimination of liquid helium requirements make it advantageous for research environments with limited helium availability.