| 其他摘要 | Using high-dispersion spectrograph for measuring the radial velocity of an observed target is an important means in astrophysical research, such as in the search for exoplanets, measuring the expansion rate of the universe, and studying the structure and evolution of stars. High-dispersion spectrograph have become essential scientific instruments in many astrophysical fields, including the search for exoplanets, measuring the expansion rate of the universe, and studying the structure and evolution of stars. As these fields of study continue to advance, there is an increasing demand for higher accuracy in radial velocity measurements using high-dispersion spectrograph. Currently, high-precision radial velocity measurements using high-dispersion spectrograph with laser frequency comb calibration sources and simultaneous calibration techniques have obvious advantages. The LiJET spectrograph installed on the 2.4-meter telescope in Lijiang is equipped with two optical fibers that can be used to introduce target sources and calibration sources for wavelength simultaneous observations. The calibration source uses a thorium-argon lamp and iodine absorption lines. The instrument is currently in trial observation and further research is needed on the simultaneous calibration data. In the future, it may be upgraded to include a laser frequency comb calibration source. In laser frequency comb calibration observations, laser speckle problems will seriously affect the radial velocity measurement accuracy, and the laser speckle problem must be solved to ensure the accuracy of radial velocity measurements. This paper studies the main problems faced by high-dispersion spectrograph in synchronous calibration, and the research content includes the following five aspects: First, for the LiJET spectrometer thorium-argon lamp synchronous calibration data, a set of data processing procedures was developed specifically for LiJET to achieve consistency and standardization in data processing results. These procedures can perform image preprocessing, spectral order positioning, and spectrum extraction, and determine the wavelength resolution and wavelength calibration accuracy of the LiJET spectrometer based on different precision atmospheric absorption line series and the standard spectrum of the thorium-argon lamp. During the extraction of spectral orders, 33 orders were extracted, two more than the designed number of orders, which maximizes the potential of the instrument and expands the wavelength coverage of the instrument. Second, for the synchronous calibration data of LiJET spectrometer using iodine absorption spectrum as the standard source, the data processing program developed for LiJET spectrometer was used to process the synchronous calibration data. The data flow was modularized based on function, and different modules could be run in the order of the flow, but were also independent of each other. Therefore, by modifying a few parameters in the modules, the synchronous calibration data of iodine absorption spectrum could be processed. And based on the template of iodine absorption spectrum, the wavelength solution and calibration precision of individual spectral order of LiJET spectrometer were obtained. Third, conduct simultaneous calibration, not only to evaluate the calibration accuracy of the instrument itself, but also to test the stability of the instrument. This part mainly uses the trial observation data of thorium-argon lamp spectrum obtained within 10 days by LiJET spectrometer to calculate the instrument drift within 10 days, thereby evaluating the stability of LiJET spectrometer. During this period, most of the calculations can be directly used from the modules developed for the LiJET spectrometer data processing process, while some modules need to be modified according to the calculation requirements by changing some parameters. Fourth, in order to solve the problem of laser speckle when using a laser frequency comb as a reference source, an experiment was conducted in the laboratory to suppress laser speckle using a deformation mirror. In the experiment, a helium-neon laser was used as one of the teeth of the laser frequency comb, and the results of speckle suppression for a spectrometer with a resolution of R=100000 were that the error in the radial velocity measurement caused by speckle centroid drift was approximately 19.8 cm/s. The main advantage of this method is that it not only improves the speckle problem, improves wavelength calibration accuracy and energy utilization rate, but also reduces the risk of affecting the service life of the optical fiber. Fifth, the existing speckle suppression system was improved by using a deformation mirror and a swing mirror in a closed-loop control, which achieved the suppression of speckle at the exit of the optical fiber while reducing the risk of affecting the service life of the optical fiber and without loss of optical intensity. This system not only improved the speckle signal-to-noise ratio and stabilized the speckle centroid, but also provided an alternative solution for future high-dispersion spectrometers to improve radial velocity measurement accuracy. The research work and research results of this thesis have certain significance for the LiJET spectrometer and high-dispersion spectrometers that use a laser frequency comb as a reference source for radial velocity measurement. For the software aspect of synchronous calibration, an automatic data processing program was developed based on the trial observation data of LiJET spectrometer synchronous calibration, with the aim of making the original spectral data processing more convenient and ensuring consistency and standardization of the data processing results. For the hardware aspect of synchronous calibration, two suppression systems for laser speckle were set up in the laboratory using deformation mirrors and swing mirrors, with the aim of improving the synchronous calibration accuracy of the next-generation high-dispersion spectrometer with a laser frequency comb as the calibration source. |
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