分类： 天文学 >> 天文学 提交时间： 2023-02-19
摘要： Motivated by the necessity of a high-quality stray light control in the detection of the gravitational waves in space, the spot size of a flat top beam generated by the clipping of the Gaussian beam (GB) is studied. By adopting the mode expansion method (MEM) approach to simulating the beam, a slight variant of the definition of the mean square deviation (MSD) spot size for the MEM beam is proposed. This enables us to quickly estimate the spot size for arbitrary propagation distances. Given that the degree of clipping is dependent on the power ratio within the surface of an optical element, the power ratio within the MSD spot range is used as a measure of spot size. The definition is then validated in the cases of simple astigmatic Gaussian beam and nearly-Gaussian beam profiles. As a representative example, the MSD spot size for a top-hat beam in a science interferometer in the detection of gravitational waves in space is then simulated. As in traditional MSD spot size analysis, the spot size is divergent when diffraction is taken into account. A careful error analysis is carried out on the divergence and in the present context, it is argued that this error will have little effect on our estimation. Using the results of our study allows an optimal design of optical systems with top-hat or other types of non-Gaussian beams. Furthermore, it allows testing the interferometry of space-based gravitational wave detectors for beam clipping in optical simulations. The present work will serve as a useful guide in the future system design of the optical bench and the sizes of the optical components.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
摘要： In space-based gravitational wave detection, the estimation of far-field wavefront error of the distorted beam is the precondition for the noise reduction. Zernike polynomials is used to describe the wavefront error of the transmitted distorted beam. The propagation of a laser beam between two telescope apertures is calculated numerically. Far-field wavefront error is estimated with the absolute height of the peak-to-valley phase deviation between distorted Gaussian beam and a reference distortion-free Gaussian beam. The results show the pointing jitter is strongly related to the wavefront error. Furthermore, when jitter decreases 10 times from 100 to 10 nrad, wavefront error reduces for more than an order of magnitude. In the analysis of multi-parameter minimization, the minimum of wavefront error tends to Z[5,3] Zernike in some parameter ranges. Some Zernikes have a strong correlation with wavefront error of the received beam. When the aperture diameter increases at Z[5,3] Zernike, wavefront error is not monotonic and has oscillation. Nevertheless, wavefront error almost remains constant with the arm length increasing from 10$^{-1}$ Mkm to 10$^3$ Mkm. When the arm length decreases for three orders of magnitude from 10$^{-1}$ Mkm to 10$^{-4}$ Mkm, wavefront error has only an order of magnitude increasing. In the range of 10$^{-4}$ Mkm to 10$^3$ Mkm, the lowest limit of the wavefront error is from 0.5 fm to 0.015 fm, at Z[5,3] Zernike and 10 nrad jitter.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
摘要： In space-based gravitational wave detection, the estimation of far-field wavefront error of the distorted beam is the precondition for the noise reduction. Zernike polynomials is used to describe the wavefront error of the transmitted distorted beam. The propagation of a laser beam between two telescope apertures is calculated numerically. Far-field wavefront error is estimated with the absolute height of the peak-to-valley phase deviation between distorted Gaussian beam and a reference distortion-free Gaussian beam. The results show the pointing jitter is strongly related to the wavefront error. Furthermore, when jitter decreases 10 times from 100 to 10 nrad, wavefront error reduces for more than an order of magnitude. In the analysis of multi-parameter minimization, the minimum of wavefront error tends to Z[5,3] Zernike in some parameter ranges. Some Zernikes have a strong correlation with wavefront error of the received beam. When the aperture diameter increases at Z[5,3] Zernike, wavefront error is not monotonic and has oscillation. Nevertheless, wavefront error almost remains constant with the arm length increasing from 10$^{-1}$ Mkm to 10$^3$ Mkm. When the arm length decreases for three orders of magnitude from 10$^{-1}$ Mkm to 10$^{-4}$ Mkm, wavefront error has only an order of magnitude increasing. In the range of 10$^{-4}$ Mkm to 10$^3$ Mkm, the lowest limit of the wavefront error is from 0.5 fm to 0.015 fm, at Z[5,3] Zernike and 10 nrad jitter.
分类： 光学 >> 量子光学 提交时间： 2023-02-19
摘要： In space-based gravitational wave detection, the estimation of far-field wavefront error of the distorted beam is the precondition for the noise reduction. Zernike polynomials is used to describe the wavefront error of the transmitted distorted beam. The propagation of a laser beam between two telescope apertures is calculated numerically. Far-field wavefront error is estimated with the absolute height of the peak-to-valley phase deviation between distorted Gaussian beam and a reference distortion-free Gaussian beam. The results show the pointing jitter is strongly related to the wavefront error. Furthermore, when jitter decreases 10 times from 100 to 10 nrad, wavefront error reduces for more than an order of magnitude. In the analysis of multi-parameter minimization, the minimum of wavefront error tends to Z[5,3] Zernike in some parameter ranges. Some Zernikes have a strong correlation with wavefront error of the received beam. When the aperture diameter increases at Z[5,3] Zernike, wavefront error is not monotonic and has oscillation. Nevertheless, wavefront error almost remains constant with the arm length increasing from 10$^{-1}$ Mkm to 10$^3$ Mkm. When the arm length decreases for three orders of magnitude from 10$^{-1}$ Mkm to 10$^{-4}$ Mkm, wavefront error has only an order of magnitude increasing. In the range of 10$^{-4}$ Mkm to 10$^3$ Mkm, the lowest limit of the wavefront error is from 0.5 fm to 0.015 fm, at Z[5,3] Zernike and 10 nrad jitter.
分类： 物理学 >> 核物理学 提交时间： 2016-08-31
Ying Zhang
Jing Huang
Ding Chen
Liu-Ming Zhai
Xu Chen
Xiao-Bin Hu
Yu-Hui Lin
Hong-Bo Jin
Xue-Yao Zhang
Cun-Feng Feng: Huan-Yu Jia
Xun-Xiu Zhou
DANZENGLUOBU
Tian-Lu Chen
LABACIREN
Mao-Yuan Liu
Qi Gao
ZHAXICIREN
摘要： A new hybrid experiment has been constructed to measure the chemical composition of cosmic rays around the "knee" in the wide energy range by the Tibet ASγ collaboration at Tibet, China, since 2014. They consist of a high-energy air-shower-core array (YAC-II), a high-density air-shower array (Tibet-III) and a large underground water-Cherenkov muon-detector array (MD). In order to obtain the primary proton, helium and iron spectra and their "knee" positions in the energy range lower than 1016 eV, each of PMTs equipped to the MD cell is required to measure the number of photons capable of covering a wide dynamic range of 100 - 106 photoelectrons (PEs) according to Monte Carlo simulations. In this paper, we firstly compare the characteristic features between R5912-PMT made by Japan Hamamatsu and CR365-PMT made by Beijing Hamamatsu. This is the first comparison between R5912-PMT and CR365-PMT. If there exists no serious difference, we will then add two 8-inch-in-diameter PMTs to meet our requirements in each MD cell, which are responsible for the range of 100 - 10000 PEs and 2000 - 1000000 PEs, respectively. That is, MD cell is expected to be able to measure the number of muons over 6 orders of magnitude.
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