| The Gravitational Wave High-energy Electromagnetic Counterpart All-sky Monitor(hereinafter referred to as GECAM)is a satellite project designed for detecting gravitational wave gamma bursts.As a space science satellite borne detector,GECAM can have its accurate ground calibration basically guarantee acquisition of effective observation data from space science satellites in orbit,which plays an important role in achieving its scientific objectives.Ground calibration mainly undertakes to calibrate the key physical parameters of satellite-borne detectors accurately,such as detection efficiency,energy response and position response.In order to achieve its scientific objectives,the ground calibration of satellite payload is particularly important.This Paper mainly covers such research contents as follows:1)Research on upgrading and improvement of a monoenergetic X-ray calibration device based on X-ray machine.The calibration device based on X-ray machine uses a crystal monochromator to have realized monoenergetic X-rays continuously adjustable within the energy range of the(8-160)keV via the Bragg diffraction principle.According to different energy ranges,calibration devices can be subdivided into monocrystal and bicrystal calibration devices.Therein,for monocrystal calibration devices,the energy range of monoenergetic X-rays is(8-40)keV,featuring good device stability better than0.56%;bicrystal calibration devices use Si220 and Si551 crystals,able to realize monoenergetic X-rays continuously adjustable within the energy range of(40-160)keV,with the device stability better than 0.55%;the stability of the monoenergetic beams has been greatly improved by perfecting the structure of the bicrystal monochromator.By changing the size of the beam-limiting aperture,the adjustable spot diameter of φ(1-12)mm has been achieved,which can satisfy the requirements of detectors for beam-limiting spots different in size.2)Research and establishment of standard detectors.Essentially,the ground calibration is to trace the measurement results of the to-be detector to the national radioactivity reference device for ensuring the accuracy and reliability of the calibration results.In the current research,high-purity germanium(HPGe)detectors are selected as standard detectors.The establishment of standard detectors mainly includes theoretical calculation and experimental calibration.It used Monte Carlo simulation software to establish a standard detector model,by setting the parallel incidence of the monoenergetic X-ray source to work out the detector response to monoenergetic X-rays different in energy and thus get the detection efficiency.Moreover,the standard radiation source is used to achieve the experimental calibration of the detection efficiency,and the point source extrapolation method is adopted to approximate the detector response to the point source to the result worked out based on the theory for verification of parallel source incidence.In the experiment,several radioactive sources in this energy range were selected to have verified the detection efficiency curve based on theoretical calculation and obtained the all-round peak detection efficiency of all energy points of HPGe detectors within the energy range of(0-300)keV,which has provided accurate data guarantee for calibrating GECAM satellite payload detectors.3)Research on the calibration of GECAM satellite payload detectors.The data analysis and research has been carried out against the detection efficiency,energy response and position uniformity of the gamma ray detectors(GRD)with the probes numbered as:Z01-28,Z01-65,Z01-56 and Z01-43.As can be seen from the results of data analysis,the detectors(Z01-28 and Z01-65)have the detection efficiency in good agreement with the simulated detection efficiency;with the increase of energy,the detector(Z01-56)can have better and better energy resolution,especially for high-energy particles;as can be seen from the calibration data of the detector(Z01-43),its probe is excellent in position uniformity. |
