Preparation And Properties Of The Niobium Film On Copper Surface

The relevance of energy with national security,social stability and sustainable economic development has motivated countries around the world to find new and sustainable clean energy,among which the nuclear energy is recognized as the clean energy for the future.With the increasing of global installed capacity of nuclear power,the problem of the pollution of spent fuel has become more and more critical.The storage of uranium resources in China is relatively low compared to its large consumption of nuclear power.In order to improve the utilization of uranium resources and solve the problem of post-treatment of spent fuel,China has developed an accelerator-driven advanced nuclear energy system,which can increase the utilization rate of uranium resources to over 95%,and the total amount of nuclear waste reduced to less than 4%of spent fuel,and the radioactive life has been reduced from 100,000 years to less than 500 years.The research of this device is of great significance to China’s energy strategy and the development of the nuclear industry.The basis of the accelerator to drive the advanced nuclear energy system is the high-current continuous wave superconducting proton accelerator.The RF superconducting cavity is a key component of the superconducting accelerator.The existing RF-based superconducting accelerator technology based on pure helium cavity has great contradiction between flow intensity,stability and cost.The use of a copper-based Niobium-plated film superconducting RF cavity not only can solve the above contradictions,but also is expected to stabilize the accelerator in a 4.2 K environment,so the Niobium-plated cavity is the future development trend of RF superconducting accelerators.In this paper,the sputtering was performed on the copper surface by DC-bias diode sputtering method.The effects of substrate temperature,workpiece negative bias and vacuum on the microstructure of the copper surface were studied.At the same time,the research on the preparation technology of the Niobium film on the surface of copper RF cavity was carried out.The Niobium film prepared on the surface of oxygen-free copper by DC-bias diode sputtering increases the surface roughness and film thickness and decreases the surface impurity content as the substrate temperature increases.With the increase of the negative bias of the workpiece,the surface roughness,thickness and impurity content of the Niobium film are reduced.As the degree of vacuum increases,the thickness of the film increases,and the surface roughness and impurity content of the ruthenium film decrease first and then increase.The Niobium film covering the entire surface of the cavity was prepared on the RF cavity by DC-bias diode sputtering.The results showed that the surface roughness and film thickness of the inner conductor are generally higher than that of the outer conductor,and the impurity content of the film is generally lower than that of the outer conductor.The content of impurity elements in the film layer at the bottom of the cavity is lower than the content of impurities in the remaining positions in the cavity.The Niobium film on the inner surface of the oxygen-free copper RF cavity has superconducting properties at a temperature of 4K.Except for the top of the outer conductor,the superconducting transition temperature of other niobium films reached 9.3K,which is equivalent to the pure niobium block.