Simulation Research On The Focused High Energy Ion Microbeam Technology

The focused high energy ion microbeam facility is a special electromagnetic device that focuses the ion beam to the micrometer level.The current several Me V ion microbeam facilities are mainly used in the field of elemental analysis and other applications,which are difficult to meet the research requirements of high energy ionizing radiation.Therefore,tens of Me V and Ge V order of high energy ion focused microbeam technology has been explored.The focused high energy ion microbeam technology can be applied to radiation effects in space science,radiation biological effects and low dose effects in proton and heavy ion cancer research and other research on radiation science.Narrow focused high energy ion microbeam technology includes collimation technology and ion optics design method.At present,the focused lens system with high magnetic rigidity or high demagnification has been understood well.However,a focused lens system with both high magnetic rigidity and high demagnification is not found.The microbeam technology is more difficult for higher energy and a larger range of ions.The range of proton is larger than that of heavy ion.Considering the beam parameters of the 300 Me V proton synchrotron proposed in Harbin,this paper aims to study how to solve the stray particle problem of the collimation system and to achieve the design of focused lens system with high demagnification and high magnetic rigidity.In the research of collimation technology,the interaction between 300 Me V proton and tungsten target was analyzed by Geant4 modeling,and the characteristics of 300 Me V proton transporting through the conversional collimation system was investigated.Therefore,a bending collimation system was proposed to separate charged stray particles from the 300 Me V proton beam,reducing the influence of stray particles generated by the interaction between 300 Me V proton and slit material.The structure of bending collimation system can be applied to different proton energy and slit materialIn the research of the design method for a focused lens system,this paper proposed the reference curve to select quadrupole magnet length based on the magnetic rigidity of ion.The method is based on the research on the strong focusing principle of quadrupole magnet.Therefore,the improvement of the focusing ability of a quadrupole magnet addresses the problems to focus Ge V protons using conventional quadrupole magnet.In this paper,a focused lens system,which has the advantages of high demagnification and low aberration coefficient,was found to achieve a 300 Me V proton microbeam based on a synchrotron accelerator.It is theoretically proved that synchrotron accelerater is also possible to construct a high energy ion microbeam facility.In the research of the optimization method of spherical aberration in a focused lens system,this paper studied the influence of fringing field of quadrupole magnet on the 300 Me V proton focused lens system.This paper studied the method of compensating the spherical aberration of the 300 Me V proton focused lens system by using octupole magnet.In order to rebuild the magnetic field,the Enge model was used to fit the magnetic field distribution of quadrupole magnet,which was simulated by finite element method.The Enge model improves the accuracy of spherical aberration coefficient calculated by the raytracing method.The difference of the calculation of the spherical aberration coefficient between by the PRAM software and the Win TRAX software was found when use the rectangular model.The introduced fringe field by Enge model narrows the difference.This paper introduces the spherical aberration contributed by quadrupole magnet and octupole magnet and the optimization method of spherical aberration.The contribution of the spherical aberration of a single octupole magnet at different positions of the microbeam system is quantitatively studied.The one octupole lens reduces the spherical aberration of the separated Russian quadruplet microbeam system effectively.In summary,the simulation research on the focused high energy ion microbeam technology,solved the problems associated with the key technologies of a high energy ion microbeam facility based on synchrotron,expanding the types of accelerator used in a microbeam facility.This paper improved the ion energy for the microbeam technology,which provides a new idea for the construction of a higher energy ion irradiation research platform and will promote the application of high energy ion microbeam facility in space science,radiation biology,nuclear medicine,nuclear agronomy and other disciplines.