R&D Of X Ray Full Scattering Device With High Magnetic Field

The X-ray full scattering pair distribution function(PDF)technology is a unique and advantageous three-dimensional atom-local and nanometer-scale(can reach hundreds of A)of local structure research methods in materials.It is playing an increasingly important role in the scientific field.Some PDF devices in the world already possess the functions of variable teperature and voltage transformation,but they are still without in combination with magnetic fields.This paper was supportted by the scientific research project of the Chinese academy of sciernces "The development of X-ray full scattering device under high magnetic field".The main content plans to develop a complete X-ray scattering system with high magnetic field to realize high precision X-ray full scattering PDF(corresponding to the locaized structure)and Xray diffraction(corresponding to the average structure)under variable temperature(5-300K)and variable magnetic field(0-10T)conditions.Firstly,on sufficient investigation of domestic and international progress in this field,this paper has completed the selection of X-ray diffraction equipment and variable temperature sample holder.Bruker' s D8 discover goniometer be selected as the experimental platform The platform technology is mature,it has a large diffraction circle radius,and the distance from the goniometer to the diffraction circle is large.Secondly,the cryostat system compatible with X-ray full scattering system and 10T separated coil superconducting magnet were been built.The system includes cryogenic sample chambers,G-M refrigerator,helium tanks,dry pumps,temperature controllers,flow meters,and three-dimensional mobile platforms.Lastly,according to the physical requirements for magnetic fields of X-ray diffraction measurement devices,the superconducting magnet adopts a separated structure with wide angle optical window.Its cold slit width is 40imi for X-ray diffraction measurement and provides a l0mm width wedge slit within 160 degrees.The superconducting magnet was designed using Nb3Sn wire and N)Ti wire.The winding consists of a pair of interpolated Nb3Sn coils and a pair of NbTi coils,which providing center field of 10T.According to the 10T magnetic field under X-ray scattering device of separation superconducting magnet system structure design,firstly,this paper make use of many coil superconducting magnet high precision magnetic field calculation programme to carry out magnetic field design and the calculation of electromagnetic parameters of the separation superconducting magnet system.Secondly,the main coil structure of the superconducting magnet system was been designed,which is the two pairs of separated superconducting coils with the center magnetic field intensity of 10T.The Nb3Sn superconducting coil windings are compactly,impregnated with epoxy and reinforced with stainless steel wire.NbTi superconducting coil windings are compactly and reinforced with stainless steel wire.In addition,the cryogenic system of the superconducting magnet system adopts the GM refrigerator,the first-stage cold head is 50K/35W and the secondary cold head is 4.2K/1.5W,and adopts two pairs of high-temperature superconducting current leads to perform closed loop operation and maintain zero evaporation.The quench protection system uses voltage limiting resistor protection(passive protection)to perform segment protection.The superconducting magnet system adopts a special superconducting magnet DC power supply(200A/10V)for power supply.Due to the high magnetic field separated of Nb3Sn close wound magnet was first time to developed in the domestic,its manufacturing technology has certain challenges.In order to complete the development of the magnet successfully,before the formal winding of the magnet,this paper has done lot s of pre-research work.The pre-research work has solved a series of critical technical problems of the separated of Nb3Sn close winding magnet.In the pre-research work,the superconducting wire's insulation process and the magnet skeleton's insulation process,the low-resistance magnet's joint process of Nb3Sn-Nb3Sn wire and Nb3Sn-NbTi wire,the magnet's heat treatment process,and the magnet's epoxy curing process were been solved.With the solution of the critical process,it has laid the process technological foundation for the subsequent magnet manufacture.