Measurement of the thermal expansion of bulk metallic glass in cryogenic temperature with a laser displacement method

The thermal expansion of structural components is a very important factor when designing cryogenic equipment such as cryocooler or superconducting equipment. However, conventional thermal expansion measurement systems require calibration of the sensor of the measurement system at cryogenic temperature, making measurement difficult. Therefore, in this study, we developed a new thermal expansion measurement system that can measure thermal expansion more conveniently than conventional measurement systems. Thermal expansion was measured using laser displacement units installed outside the vacuum vessel. Moreover, a conduction cooling system using a 4K-GM cryocooler was adopted for cooling. To confirm the effectiveness of the developed system, the thermal expansion of copper, a well-known material, was measured using this system, and the results were consistent with that of a previous study. The thermal expansion of bulk metallic glass, which is expected to be used in cryogenic environments, was measured using the developed system, and it was found to be -0.23% at cryogenic temperatures, smaller than that of other typical materials such as copper and aluminum.