Research On Core Materials For Neutron Detecting Fiber Conduction Materials

With the rapid development of medical imaging,space imaging,space physics research,nuclear physics,resource detection and other technologies,the demand for detection materials in all fields is increasing,and higher requirements have been put forward for the research of scintillation materials.Among all scintillation materials,scintillation glass materials have the advantages of simple preparation process,low cost,easy adjustment of components and high production efficiency.So it is expected to be the preferred material suitable for civil field.Optical fiber has excellent signal transmission function and is expected to realize real-time remote transmission of scintillation detection signals.So it is imperative to study scintillation glass fiber materials.The purpose of this paper is the application of neutron detection by optical fiber materials.Glass samples were prepared by using melt quenching method.A series of rare earth ions doped borosilicate glass samples were investigated through a series of equipment to analyze the structure,physical and optical properties to look for the best performance of the glass samples.In Chapter 3,the matching of matrix glass is studied.Firstly,according to the different roles of different components in glass,the main glass components are determined to be B₂O₃-Si O₂-Al₂O₃-Na₂O-Ba O-La₂O₃.Secondly,according to the refractive index and thermal expansion coefficient,the addition amounts of sodium oxide and lanthanum oxide were determined.The final composition of the glass matrix is 60B₂O₃-6Si O₂-3Al₂O₃-5Ba O-1Sb₂O₃-15Na₂O-10La₂O₃（BSA-BNL8）.It can match the cladding glass better.In Chapter 4,the effects of different Ce O₂ content on the structure,physical and optical properties of glass samples were studied.The results show that the incorporation of Ce³⁺has no significant effect on the glass network structure,and Ce³⁺mainly exists in the form of network modifiers.The transmittance reaches about75%and the UV absorption edge is lower than 400nm.With the increase of Ce³⁺,the optical band gap is shortened to 2.93e V.All these factors are very conducive to Ce³⁺luminescence.The peak center of emission spectrum is 370nm when it is pumped by a 306nm excitation source.The optical alkalinity increases with the increase of Ce³⁺concentration（0.5392～0.5417）,which results in a red shift of emission spectrum.The results of fluorescence lifetime test are as low as 24.39ns,which indicates that the glass sample has excellent scintillation performance.In Chapter 5,the effects of Gd₂O₃were studied in structure,physical and optical properties of borosilicate glass.The results show that the incorporation of Gd³⁺has no significant effect on the glass network and Gd³⁺also exists in the form of modifier.The transmittance of glass is about 65%and the UV absorption edge is lower than400nm.The optical band gap is shortened to 3.24e V while the optical alkalinity（0.4941～0.5063）increases with the increase of Gd³⁺concentration.All these factors are beneficial to the optical band gap transition.The maximum emission spectrum of330nm excitation source is 375nm in Ce³⁺-doped samples.Combining with the excitation and emission spectra of Gd³⁺singly doped sample,it indicates that Gd³⁺can effectively transfer energy to Ce³⁺and improve the luminous efficiency of Ce³⁺.At the same time,the minimum fluorescence lifetime was 30.99ns,indicating that Gd³⁺does not affect the scintillation performance of Ce³⁺.Additionally,under the X-ray excitation,the emission peak of G2 sample is at 374 nm,indicating that the emission peak of Ce³⁺is less affected by the wavelength of the excitation source when it is shorter than 330nm.In Chapter 6,based on the results of the above studies on the physicochemical properties and Ce ion luminescence properties of the borosilicate glass,it is determined that G2 glass matches the identified cladding glass better in physicochemical properties and possesses stronger Ce ion luminescence properties and shorter lifetime.The position of the core is determined by using COMSOL Multiphysics software that the distance between adjacent fiber cores（Λ）is 40μm.When the core radius（a）is 5μm the pattern of transmission mode distribution is best.Fiber drawing is carried out according to above simulation results.The outer diameter of the fiber is about 200μm with four cores.By using the 330nm excitation source pump,the maximum value of emission spectrum is 375nm,which is basically consistent with the emission peak of G2 glass sample.The luminous peak wavelength of Ce³⁺has no obvious change after the glass fiber drawing.To sum up,compared with the same type of scintillation materials doped with rare earth ions borosilicate glass,it has obvious advantages.Scintillation glass fiber materials studied in this paper provide a new material choice for the development of neutron detection technology.