RARE-EARTH COLD STORAGE MATERIAL PARTICLE, RARE-EARTH COLD STORAGE MATERIAL PARTICLES, REFRIGERATOR UTILIZING SAME, MEASURING DEVICE, AND METHOD FOR PRODUCING SAME

摘要

Disclosed are rare-earth cold storage material particles having an average particle size of 0.01-3mm, characterized by the proportion of particles having a length/width ratio of no more than two being at least 90% by number, and the proportion of particles with a depression formed having a length that is 1/10-1/2 of the length of the circumference of the particle surface being at least 30% by number. By means of the cold storage material particles having a depression formed on the surface, the contact surface area with a working medium gas as well as the permeability to the working medium gas can be increased.