Investigation of the photomultiplier tubes radiation response and its coping strategy

Despite being thought as a kind of near-ideal light signal amplifier, photomultiplier tubes actually will add an additional contribution to the output signal of scintillation detectors when being irradiated. The contribution is rather small for those detectors consisted of various high-yield scintillators and is thought for a long time to not produce any adverse impact. In the paper, through simulation analysis and well-designed reversed experiment, it is demonstrated that not only being widely accepted Cherenkov emission but also fluorescence emission in the input window both plays great role in the additional contribution. Furthermore, it is also verified through experiments that the radiation conversion performance of this contribution is different or even lower than that of common inorganic scintillators. This leads that the merits of low-yield scintillators are lost in coaxial detector and some measurement results corrected based on the standard performance of the scintillators are usually incorrect. To reduce the adverse impact and acquire the requested performance of some new low-yield scintillators, a kind of off-axis detector layout is designed and proved to be effective. (paper)