放射源活度的符合测量.doc

放射源活度的符合测量专业:核工程与核技术摘要:本实验选用了两片相同的铝片夹住的点源作为正电子源,,在短时间的测量过程中不用考虑其活度的变化。可经过EC俘获衰变到的激发态,%,也可经过β+衰变到的激发态,%,再从激发态衰变到基态,,也能直接衰变到基态,%。产生的正电子在铝片中慢化后遇电子发生湮没,,湮灭光子发射方向相反且各向同性,。探测仪器选用了γ射线探测效率高、能量分辨率好的NaI闪烁体探测器,实验系统采用了传统的符合测量装置,即两组NaI闪烁体探测器,放大器,单道,定标器,外加符合电路的组合。用此套装置很好的测出了的能谱,保证了整个装置完好。由于两种能量的光子都能被探测器探测到,所以通过测出了的能谱,调节单道的道宽和下阈值,,-γ符合测量,测出了的活度,其活度是24353±162(Bq)。关键词:点源湮没光子γ-γ符合法Abstract:Inthisexperiment,wechosedapointsourcewhichissandwichedbytwosamealuminumfoil,andwhosehalf-,,%,alsocandecaytotheexcitedstateofthroughβpositivedecay,%,againfromtheexcitedstateofdecaytothegroundstateof,,directlydecaytothegroundstateof,%.Thereleasedpositronsenterintothealuminiumandslowdownquickly,thenwhichhappenfloodedwithnegativeelectronandemittwophotonsγ,whoseenergyisthesame,,andthedirectionofemissionoftwophotonsiscounterandisotropic,,theexperimentsystemisthetraditionalmeasuringdevice,consistingoftwoNaIscintillationdetector,amplifier,singlechannel,thescaler,,sowemeasuredtheenergyspectrumof,andadjustedthewayofthesinglechannelwidthandthethreshold,,,andmeasuredtheactivityof,theactivityis24353±162(Bq).Keywords:pointsourceAnnihilationphotonγ-γCoincidencemethod目录第一章绪论 1第二章方案原理概述 -γ快符合装置介绍 4第三章技术路线的实现