Development Of Scintillation Crystal Czochralski Method Equipment,and Growth Of YSO:Ce Scintillation Crystal With Large Size

Czochralski is one of methods of growing crystal from melt?molten state raw materials?,which is invented by J.Czochralski and named by his name.This method is mainly used for important crystals such as sapphire and yttrium aluminum garnet.The advantage of it is easy to observe and monitor,simple operation,high quality of crystal and automatic growth of crystal.In order to further improve the quality and yield of scintillation crystal,it is tendency to improve traditional equipment and growth of crystal with big size.In this thesis,a new type of crystal strove aiming at growth of rare earth oxide scintillation crystal has been designed,which has distributed control system and is combined with expect PID control and adaptive PID control.Since control module and the host computer become independent of each other,control of crystal growth can be out of the host computer software and avoid hidden dangers caused by the PC computer failure.Even using a host computer to control multiple crystal stoves,greatly reduces the manual management and production costs.In the automatic control of crystal growth,using expert adaptive PID controller to compare the actual weight value with theoretical value,and then achieve automatic crystal growth through the output of the intelligent controller.In this thesis,the growth of Ce:YSO scintillation crystals was studied.YSO?Y₂SiO₅?was first discovered in 1963.YSO as a good matrix material can achieve different functions by doping different rare earth ions.Ce³⁺doped YSO scintillation crystal is widely used in radiation detection because of its high light output and fast decay time.In this paper,using self-developed Czochralski crystal growth equipment successfully grew a number of large-size scintillation crystals.The maximum length of the crystals is more than 200mm.After optimization of crystals,the optical performance was tested to verify the performance of the equipment.The results show that the automatic control system has high control precision and response speed,and high quality crystals with diameter of80mm and length of 200mm successfully grow up.The crystal has uniform composition,good luminous performance,420nm wavelength light transmittance as high as 80%and9%energy resolution.The crystal is transparent and no obvious internal defects could be seen,which can be used as radiation detection materials.