Development Of NVST High Resolution Magnetograph Control System

In order to obtain high resolution solar magnetic field data,the NVST magnetograph uses the technology of "same optical path with different structure image reconstruction".The atmospheric transfer function is obtained through a photosphere image with a high SNR to reconstruct a narrowband polarization image with a low SNR.This puts high requirements on data acquisition and control.The first is how to obtain a large number of short-exposure spot images of two channels continuously and at high speed,and ensure that each frame of two channels is strictly synchronized in time and space.The second is how to ensure that a set of sequence spot images used for statistical reconstruction are strictly synchronized with the polarimetry's modulation state.For this reason,the related research work of NVST magnetograph control system is carried out in this paper.Firstly,the paper introduces the design idea of NVST high resolution magnetograph,the key technology used and the development of related technologies at home and abroad.The requirements of the control system of the magnetograph based on the same optical path with different structure image reconstruction technology are analyzed.The key points and difficulties of the control system are described.And the overall structure design and basic work flow of the system are given.It focuses on how to implement a series of short-exposure burst images with two channels in continuous acquisition under high temporal and spatial accuracy synchronization.The detailed synchronization timing design of the system and the frame exposure timing synchronization test results of the two-channel sCMOS camera are given.The synchronous acquisition experiment was carried out,and the high resolution statistical reconstruction results of the synchronously acquired spot images were given.It was proved that the system structure and timing can meet the requirements of the “same optical path with different structure image reconstruction” technology for sequence spot images acquisition.Then two sets of polarimetry analyzers of NVST high resolution magnetograph are introduced in detail: the basic principle of polarization modulation based on KD*P and rotating wave plate,and the requirements for the synchronization of polarization modulation and two-channel sequential spot images,respectively.In this kind of polarization modulation test,synchronous control timings were designed and related tests and experiments were carried out.The polarization images of the NVST high-resolution magnetic imager on the sun disk were initially obtained.Through detailed analysis and design of NVST high-resolution magnetograph control system,as well as a large number of tests and experiments.It is demonstrated that the control system can meet the functional and performance requirements of the NVST high resolution magnetograph.The NVST magnetograph control system can work efficiently and stably.