锯齿型外掩体设计和衍射光强检测

Design and diffraction intensity test of toothed occulter

针对太阳极轨望远镜计划对大视场日冕仪杂散光抑制的要求,设计了一个衍射抑制程度更高的锯齿型外掩体用于该日冕仪。应用半无限矩形法模拟了锯齿型外掩体衍射光强分布,得到了最低衍射强度的锯齿形状。通过实验检测了此最优锯齿形状外掩体的衍射光抑制水平,并与圆形外掩体衍射光强进行了对比,证实了锯齿型外掩体相对于圆形外掩体在抑制衍射光上的优势。实验观测结果显示,优化设计后的锯齿型外掩体的衍射光强抑制水平可以达到10-7量级,高于目前国际上实验观测到的外掩体衍射光强抑制水平10-6量级,可以满足大视场日冕仪的对杂散光抑制的要求。

According to the requirements of a coronagraph for suppressing the stray light in Solar Polar Orbit Radio Telescope Mission,a toothed occulter for the coronagraph was designed to suppress the diffracted light in a higher level.The diffracted light distribution from the toothed occulter was calculated by using the semi-infinite rectangle method,and an optimized shape with the lowest diffracted light was obtained.Meanwhile,the stray light level of the optimized toothed occulter was measured experimentally,and the obtained result was compared with the diffraction intensity of a round disk occulter.It verifies that the toothed occulter has an advantage over the round disk in diffracted light reduction.The measured data show that the suppression of diffracted light of the proposed toothed occulter has been up to 10-7 level after optimization,higher than internationally 10-6 level in the lab.The suppression level has been met the demands of large view coronagraphs.