HPCVD Thin Film MgB2 for Superconducting Magnetic Shielding

Superconducting magnetic shielding (SMS) is crucial for superconducting electronic devices such as superconducting quantum interference devices (SQUIDs). Current magnetic shielding devices suffer from high construction price, poor mobility, and flexibility. The MgB₂ SMS with cryocooler could be the potential the solution. In this work, a hybrid physical-chemical vapor deposition system, which is capable of depositing on a long cylindrical surface, is demonstrated. A dense and robust MgB₂ film has successfully been deposited on the inside wall of a Φ50 × 120 mm 304 stainless steel tube. A microscopic image indicated that the deposited MgB₂ showed a dendritic structure with cracks on it. Sample with different B₂H₆ flow rates has been made, current result showed a better performance with higher B₂H₆ flow rate. However, safety issue should be taken into consideration as we further increase the B₂H₆ concentration. The sample deposited with 10 sccm 25% B₂H₆ showed the best performance so far with a T_C of 34.4 K. A SQUID testing system specifically for high-temperature SQUID with MgB₂ SMS with a liquid-helium-free cryogenic system has been design and under construction for the future researches.