Research On Calibration Method Of Gamma Ray Monitor

In 1916,Einstein predicted the existence of gravitational waves based on general relativity.The existence of gravitational waves is the result of Lorentz invariance of general relativity.The precession or integration of dense binary systems,such as neutron stars or black-hole binary systems,may produce gravitational waves during the process of precession or merging,and gravitational waves are often accompanied by gamma-ray bursts.In order to accurately detect gamma-ray bursts,the Purple Mountain Observatory of the Chinese Academy of Sciences launched the Advanced Space-Based Solar Observatory(ASO-S)satellite in July 2018.The Institute of High Energy Physics of the Chinese Academy of Sciences established GECAM satellite engineering and SVOM satellites in December 2018.engineering.These three satellites are aimed at the study of hard X-ray,soft gamma ray energy spectrum observation and gamma ray triggering.In order to ensure that the astronomical satellite accurately performs the survey mission,accurate ground calibration of the payload of the astronomical satellite is required.Only through accurate ground calibration,the energy linearity,detection efficiency,angular response uniformity,energy resolution,position response uniformity,bias response and other physical parameters of the satellite can be used for effective data analysis of astronomical observations.Although the payload of an astronomical satellite is called a gamma-ray monitor,its energy detection range is not limited to gamma rays,but also includes X-ray energy ranges.Due to laboratory conditions,the energy range of single-energy light is(5-200)keV,and calibration with X-rays will not affect the energy linearity,detection efficiency and other indicators.And beyond the X-ray energy band calibration,an exempt source is used,but the activity of the exempt source is not enough,the photon count rate is too low,which results in a very long experiment,and the energy point is very limited due to the limitation of the type of radioactive element It is limited,the energy is not adjustable,and the radionuclide is changing from time to time.Calibration of the detection efficiency requires half-life correction and the lending of radioactive sources is cumbersome.Therefore,radioactive sources are generally not used when calibrating the detector.Therefore,laboratory calibration uses X-rays.This article mainly does the following work:1)The energy range of single-energy X-rays is extended to(35-200)keV by a twin crystal monochromator.X-rays emerge from the optical machine as a continuous spectrum,hitting the crystal,and monochromating the continuous X-rays by Bragg diffraction to obtain single-energy X-rays.The main structure of the twin crystal monochromator is a T-shaped structure and a high-precision goniometer.The T structure can ensure that the outgoing direction and position of the obtained single-energy X-ray are substantially unchanged,which simplifies the operation of the experiment.In this experiment,Si551 and Si511 crystals were used to obtain single-energy X-rays of(35-200)keV,the energy was continuously adjustable,the luminous flux stability was better than 0.3%,and the stability was good.2)With a single crystal monochromator,the energy range of single-energy X-rays is as low as(5-45)keV.The biggest problem with the conventional single crystal device is that in the process of adjusting the Bragg diffraction angle,only the crystal rotates,the optical machine does not rotate,and the outgoing direction and position of the outgoing single-energy X-ray are not fixed.Now change the device to rotate the angle θ of the crystal,and rotate the platform where the optomechanical and the crystal are located by-2θ,so that the single-energy X-ray exit direction is consistent with that before the rotation.Single-energy X-rays of(5-40)keV are obtained by using LiF crystal,the energy is continuously adjustable,and the photon flux is stable.3)After the single-energy X-ray of(5-200)keV is established,the research mainly focuses on the ground preliminary calibration of the partial payload of GECAM astronomical satellite,SVOM satellite and ASO-S satellite.The preliminary calibration of the ground surface of the GECAM satellite payload GRD is studied.The energy response,detection efficiency,position response uniformity and angular response uniformity of the GRD detector are analyzed.