Study Of Al And Zr EUV Filters

In order to achieve early warning of space weather,monitor physical processes in the Earth’s environment,and study specific spectral lines,the Extreme Ultraviolet Imager(EUVI)needs to be equipped for real-time observation.The EUV filter acts as a front filter,selecting the required band and removing unnecessary ultraviolet,infrared,and visible radiation.To enhance signal detection by the detector,this paper presents an in-depth study on the design and preparation of large aperture filters for the front filters in space-based extreme ultraviolet imagers,focusing on film system design,thin film deposition process,and performance characterization.Firstly,most materials in the EUV and soft X-ray wavelength ranges have low transmittance,so it is challenging to find the right material or combination of materials to meet the filter requirements.In order to address certain detection needs,research has been conducted on two spectral lines in the solar spectrum,specifically 17.1 nm and9.4 nm.Based on the inherent characteristics of different materials and their simulated transmittance at the operating wavelength,Al and Zr were chosen as the primary materials for mesh-supported filter development.Finite element analysis was performed on the support mesh to investigate whether the stress and deformation generated during its operation meet the requirements under random vibration and hightemperature heating conditions.Secondly,different deposition methods,such as thermal evaporation and magnetron sputtering,were chosen for Al and Zr based on their different material properties.The effects of different release layers on the metal film were studied,and Cs I was ultimately chosen as the release layer for the Al filter,while Cu was chosen as the release layer for the Zr filter.Research was conducted on the surface morphology and stress of the thin films,with a focus on the surface morphology of the Al film under different deposition rates,the stress changes of the Zr film under different sputtering pressures,and the influence of subsequent annealing temperatures on the thin films.Eventually,appropriate process parameters such as background vacuum level,deposition rate,sputtering pressure,and temperature were determined,and samples of17.1 nm and 9.4 nm Al and Zr filters were prepared.Finally,characterization experiments were conducted on the 17.1 nm Al filter sample.The results showed that the transmittance of the sample at 17.1 nm was approximately 43.81%,and the surface was smooth and free of obvious pinholes.Using an ellipsometer,the thickness of the oxide layer after completion of oxidation was calculated,and the transmittance of the filter was simulated to be 42.34%.By adjusting the layer thickness using IMD modeling of the oxide layer thickness and roughness and fitting it to the actual measured values,the simulated transmittance closely approximated the measured values,with an absolute error of approximately 1%.To improve the mechanical properties of the filters,a nickel mesh support scheme was used to increase the sample diameter from 25 mm to 65 mm.Solutions were proposed to address pinhole problems and film tear caused by random vibration tests by optimizing the filter film structure or using adhesives,etc.This study confirmed the manufacturing methods for 17.1 nm and 9.4 nm EUV filters,and provided optimization ideas with significant application value in the field of space exploration.