1.3 GHz高频铜腔磁控溅射镀铌工艺研究

Niobium Coating by Magnetron Sputtering in 1.3 GHz High Frequency Copper Cavity

相比于纯铌超导高频腔,铜腔内壁镀铌超导腔具有对直流磁场不敏感、热稳定性高、造价成本低等一系列优点,并且铜腔镀铌工艺是铜腔表面制备Nb3Sn、NbN以及超导-绝缘-超导(SIS)复合膜的基础。因此使用直流磁控溅射法在铜基底高频腔内壁进行铌膜沉积,以探索铜腔镀铌工艺。并借助于FIB、SEM、XRD对铌膜的内部缺陷、表面形貌、晶相结构进行表征分析。研究结果显示:通过控制镀膜真空室的洁净、降低镀膜时间和放电气压,以及控制磁环的运动方式,获得了铜腔轴向分布均匀,Tc值达9.26 K,表面连续性较好的铌膜。铜镀铌腔垂直测试结果显示,腔性能在Q0>108下达到了5 MV/m,对应峰值磁场24 mT。该结果为后续进一步改善镀铌质量,提高镀膜超导腔性能,以及尝试在铜基底上进行其他超导材料(NbN、Nb3Sn)的镀膜奠定了良好的基础。

Compared to high-frequency superconducting niobium cavities,superconducting high-frequency niobium coating cavities have a series of advantages such as insensitivity to DC magnetic field,high thermal stability,low cost,and the copper cavity niobium coating process is the basis for the preparation of Nb3Sn and NbN,as well as superconducting-insulating-superconducting(SIS)composite films on the surface of copper cavities.Therefore,a DC magnetron sputtering method was used to deposit niobium films on the inner wall of the highfrequency cavity of the copper in order to explore the copper cavity niobium coating process.The internal defects,surface morphology,and crystalline structure of the niobium film were characterized by means of FIB,SEM,and XRD.The results show that by controlling the dusting free of the coating vacuum chamber,reducing the coating time and discharge air pressure,and controlling the movement of the magnetic ring,a niobium film with uniform axial distribution in the copper cavity,a Tc value of 9.26 K,and good surface continuity was obtained.The results of the vertical test of the copper-plated niobium cavity showed that the cavity performance reached 5 MV/m at Q0>108,corresponding to the peak magnetic field is 24 mT,achieving superconductivity in the coated cavity.This provides a good basis for further improving the quality of the niobium film,improving the performance of the coated superconducting cavity,and attempting to coat other superconducting materials(NbN,Nb3Sn)on copper substrates.