Monte Carlo Simulation Study Of Nested Wide Energy Space Neutron Spectrometer

The development of outer space exploration and manned space flight has always been the pursuit of human beings and the driving force for the continu ance development of the humanity society.In recent years,the measurement of space neutron radiation is occupying a more and more important position with the vigorous development of international manned space flight.Exploration,de velopment and utilization of outer space resources have become one of the im portant focuses of international competition.Space environment is complicated and full of neutrons with wide range energy,neutron are not charged and sensi tive to low Z number nuclides,which can be used to explore water resources of other planet such as Mars.These features also be utilized to provide basis f or the existence of outer space body.On the other hand,most of human body components are consisted with light materials,hence,through the measurement of space radiation space can provide very important basis for radiation protect ion of astronauts and space equipment at the same time ensuring the safety of astronauts.Widespread neutrons are not only helpful to explore universe mess age but also challenging for radiation protection.Only by achieving the effecti ve measure of neutron spectrum can we provide personal safety assurance for t he staff and the surrounding residents.This paper is based on the basic scientific research project of national def ense named the measurement and calibration technology of space radiation neut ron energy spectrum,which mainly carried out the related work on the space neutron energy spectrum measurement technology.In view of the range of neut ron energy from several e V^to tens of Me V,some even reach thousands of megabytes.Available multi-sphere neutron spectrometer is composed of different sizes of polyethylene ball and metal b-all,and these different balls constitute the detection system of neutron spectrum.However,it is easy for multi-detect ion system to influence each other,which lead that the results are different ev ery time.In order to realize the measurement of the neutron spectrum in a wi de range of space neutron,this paper designs two kinds of separation and com bination neutron spectrometer which are suitable for the measurement of space neutron energy spectrum.One uses polyethylene as basic moderator,the other one uses water as a neutron moderator.The main contents of this paper are as follows:1)Selecting the central detector of the separation and combination polyeth ylene nested neutron spectrometer and the water injection nested neutron spectr ometer.³He neutron proportional detector is selected as the central detector of the two sets of nested neutron spectrometers by comparing the reaction cross s ections of three elements of ³He,¹⁰B and ⁶Li.2)Choosing moderator materials for the separation and combination polyet hylene nested neutron spectrometer and the water injection nested neutron spect rometer.Add four moderator materials such as polyethylene?PE?,water?Wate r?,paraffin?Paraffin?and heavy water?Heavy Water?in the UK's Centronic S P9 ³He proportional detector,simulating the neutron energy response trend with the material thickness changing.Finally,choosing proper polyethylene thicknes s and water thickness to response neutron below 10 Me V.3)Optimizing the structure and selecting best parameter for the separation and combination polyethylene nested neutron spectrometer.Adding auxiliary m aterials such as Cu,Pb,W into polyethylene and comparing to the several det ector designs through Monte Carlo calculation method,the suitable diameter of the spherical moderator is chosen to response neutron above 10 Me V.Optimiz ing the structure and selecting best parameter for the water injection nested ne utron spectrometer.Changing the size and structure of the slow water ball.Usi ng FLUKA to simulate the energy response of different water ball and selectin g the best parameters and structure of water ball.Designing system structure o f the separation of the combination of polyethylene nested neutron spectrometer and water extraction nested neutron spectrometer.The two sets of nested neut ron spectrometers are both in the form of nest,which realize the measurement of broad energy spectrum neutron by multiple different measurements.4)Verifying the factors that may affect the simulation results in the simul ation process,excluding the influence of them on the experimental results.Co mparing the two kinds of wide energy spectrum nested neutron spectrometer.A nalyzing the advantages and disadvantages of both of them and getting their ap plication scope.The main achievements of this paper are as follows:1)Separation combination type nested neutron spectrometer was designed,which use polyethylene as moderator material.It improves the detector respon se of neutron above 10 Me V by composing polyethylene shell and metal shell on center detector to constitute different sizes of moderator balls.The respons e can reach 1.68 times when the neutron energy is 10 Me V,and the response can separately reach 26.44 times and 120.47 times when the neutron energy is100 Me V and 1000 Me V.2)The water injection nested neutron spectrometer was designed,which u se lead glass shell to form different sizes of moderator balls,improving the de tector response of neutron above 10 Me V by injecting water into different ball shell.When the neutron energy is 100 Me V,the response of the water injecti on nested neutron spectrometer device after injecting water is more than 7.88 t imes that of the water ball with the same water depth.3)Nested neutron spectrometer ensures that the same detectors and measu rement electronics system are used every time.Therefore,it is very good to so lve the problem of the inconsistency,and it effectively avoids the error caused by multiple signal acquisition system and data processing system using the sa me signal acquisition system.The main innovations of this paper are as follows:1)The two set of neutron spectrometer are both in the form of nest.The separation of the combination of polyethylene nested neutron spectrometer use different polyethylene shells and auxiliary material shells to combine in the sa me ³He proportional counter to constitute slow balls of different sizes.And the water injection nested neutron spectrometer is regarded as a whole which cha nge the slow materials thickness by waterflood and pumping water into differe nt shells.The form of nest solves the problem that available multi sphere influ encing each other.2)The two set of neutron spectrometer both use a set of electronic syste ms to deal with subgroup data.The separation combined polyethylene nested n eutron spectrometer and water pumping from the nested neutron spectrometer e quipped with their own set of electronics system,and multiple measurement da ta are processed through their own electronic system,which overcome the Inco nsistency of existing multi system.