The RMF Of Insight-HXMT LE Telescope And Energy Calibration In-orbit

Insight-HXMT(Insight Hard X-ray Modulation Telescope,Insight-HXMT)is the first space X-ray telescope that the Chinese scientists designed using the Direct Demodulation Method which is proposed in the 1990s by processors Li Tipei and Wu Mei.The Low Energy X-ray Telescope is one important payload of the Insight-HXMT which has a total effective area of 384cm~2.The LE has a very good time response and energy resolution,which can satisfy the study of light curve and spectrum of low energy X-ray celestial body.In order to study the spectrum of the source,we must obtain the energy response of the detector,the main principle is to obtain all the energy response of the single energy X-ray in our detector.Generally,there are two ways to generate the RMF.First one is using the Monte Carlo Simulation method.The main principle of this method is that we choose some typical energy photon and measure their spectroscopy,and we can use the simulation to obtain detector's RMF according to the spectroscopy fitting results including E-C relationship,Energy-resolution relationship combined with some characterization of the detector.This method needs to convert the performance parameters of the detector into input parameters of Monte Carlo method.The process of this method is more complex.The second method is the linear interpolation method.The main principle of this method use the interpolation method to get the energy response of single X-Ray within the energy range according to the energy response in CCD236 of two single energy X-Ray,combined with the E-C relationship of the detector.This method is simple and effective,and its fitting precision can be used for the subsequent spectrum analysis.This paper mainly introduces the method of linear interpolation.The RMF is based on the energy spectrum data generated by the two-crystal monochromator calibration experiment,which is obtained by the pre-calibration device of insight-HXMT.The main components of the device includes:light source,beam line,target room and supporting system.Double crystal monochromator contains a pair of Si(111)and KAP crystals.The energy range of KAP crystals is 0.9~3.0keV,and the energy range of Si(111)crystals is 3.0~30ke V.We used the KAP crystal 0.9 2.5 keV energy response experiment,and used Si crystal for 3-15 keV energy response experiment.In KAP crystal experiment we selected the energy points with 0.929 keV,1.5keV,1.77 keV,2.03 keV and 3.0 keV.In the Si(111)crystal experiments,in the 3.5-8 keV every 0.5 keV can conduct a single experiment,8-12keV per 1 keV can conduct a single experiment.Because CCD236 performance is different under different temperatures,and the on-orbit temperature range is big,here to test working temperature is 20?70?to-every 10?for a set of experiments,a total of six groups.The calibration of the CCD236 detector was completed before the launch of the"Insight"satellite.According to the calibration work of CCD236,the E-C relationship of CCD236 detector will change with the temperature and other working conditions.In the orbit data processing,there are some errors in the energy spectrum fitting.We believe that the in-orbit work conditions of the satellite are different from the ground test conditions,so a detailed in-orbit calibration is required.The specific celestial source is selected as the calibration source.This article selects the supernova remnant Cassiopeia A,whose spectrum contains rich ion emission lines,which can be used for energy calibration.