68Ge is a kind of radioactive source widely used for calibration of positron emission tomograph(PET).A solution of 68Ge mixed with epoxy resin is poured evenly into a mold and solidified into the calibration source.In order to test the activity uniformity of 68Ge calibration source,a testing device was designed and optimized,based on the Geant4 simulation.In our simulation,the impact of several key parameters on shielding effectiveness and detection efficiency,including shield material,shield thickness,detector size and the distance between the detector and source,was studied.It shows that tungsten has the best shielding effectiveness and can be used as the inner shield.Lead can be used as the outer shield for background radiation.Changing the size of the detector has a significant impact on the detection efficiency,but with the increase in the length of the detector,the detection efficiency tends to saturate,and the source probing distance is the best overall performance at 1 cm.
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