Development and experimental teaching application of the high-resolution spectral observation system of a solar tower
[Objective]As the closest star to Earth,the Sun is a natural laboratory for detailed exploration and research on stellar activities.Like all stars,the Sun is a massive sphere composed of highly ionized gases that emit light based on its energy.Solar activities directly impact the spatial environment between the Sun and Earth as well as the habitability of our planet.Research on the Sun contributes to a comprehensive understanding of this celestial body.Therefore,more than 60 years ago,enthusiastic young scholars at Beijing Normal University overcame the lack of materials to build the first solar tower in New China.The solar tower has a vertical depth of approximately 20 meters.However,this original old observation system can no longer function effectively,owing to long-term disrepair.To reform the teaching of observational astronomy courses and enhance the quality of astronomical experimental teaching,researchers conducted on-site feasibility assessments and analyses.Subsequently,they redesigned and systematically optimized the existing hardware infrastructure of a solar tower.By leveraging the tower's long optical path,large aperture,and focal length,which are conducive to high-resolution solar spectroscopy observations,a new high-resolution solar spectroscopy observation system was successfully developed.The system consists of five subsystems:astronomical dome system,tracking mirror system,imaging optical system,grating spectrometer system,and detector system.Equipped with a GPS device,the dome system achieves a tracking accuracy exceeding 1°,rotating to follow the changing solar azimuth when the dome window is open.The dome can switch between automatic tracking(for the conventional observation mode)and manual control(for the debugging and maintenance modes).The tracking mirror system is equipped with real-time adjustment capabilities to compensate for the daily apparent motion of the sun and annual variation in solar declination.The imaging optical system employed a design featuring a long focal ratio off-axis three-mirror system.The grating spectrometer system used a 1 200 g/mm ruled flat grating with a resolution capability of 105,achieving a spectral resolution of 0.022 Å at a wavelength of 5 324 Å.The detector system used the B2020 model from IMPERX.Through effective coordination between the hardware and software control systems,the solar tower's high-resolution spectral observation system achieves high precision in the automated observational mode.The system satisfies the high-resolution observation requirements for characteristic spectral lines in the solar photosphere and chromosphere,enabling the precise study of the characteristics of sunspots and flares.Astronomy,as an observation-based discipline,emphasizes the development of astronomical observation and data-processing skills among undergraduate and graduate students.By leveraging the open optical path design and modular experimental platform of this system,researchers have integrated optical theory with practical astronomy in their systematic approach.Through the design of two innovative hands-on experimental projects,"Spectrum Shooting and Line Identification of Calibration Mercury Lamp"and"High-Resolution Solar Spectrum Shooting and Line Identification",students'interest in conducting relevant solar research is significantly enhanced from multiple perspectives.This integration of practical teaching and scientific research effectively propels the teaching reform of observational astronomy courses.
solar towerhigh-resolution spectral observationexperimental innovationtransformation of education
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