Dynamic Range Study of Microchannel Plate Photomultiplier Tubes under Visible Light Pulse Input
Microchannel Plate Photomultiplier Tube(MCP-PMT),as a high-performance photodetector,has been widely used in various detection experiments in recent years.In previous studies,people mainly focused on improving the sensitivity and temporal resolution of optoelectronic detection devices,while ignoring the key factor of high linearity.With the continuous development of the demand for large dynamic detection,in-depth research and development of MCP-PMT with large dynamic range has become an urgent need for current research.The dynamic range of MCP-PMT is related to many factors,such as the intensity and frequency of input visible light,the material of the microchannel board,and the voltage values applied to each part of MCP-PMT.This article mainly starts from two aspects:the input light pulse frequency and the potential difference applied by the backend of MCP-PMT,and delves into the reasons why the output electrons of MCP-PMT deviate from normal linear multiplication.By combining theoretical analysis and experimental testing,the influence of the repetition frequency of pulse light signals and the potential difference between the second microchannel plate and the anode on the dynamic range of MCP-PMT was studied in detail.When the input light pulse width is 50 ns and the repetition frequency is 500 Hz,the maximum linear output of the anode can reach 2 V(i.e.40 mA);when the repetition frequency increases to 1000 Hz,the linear deviation degree reaches more than 10%when the anode output is 1 V(i.e.20 mA);when the input light frequency further increases to 5000 Hz and the anode output reaches 0.3 V(i.e.6 mA),the degree of linear deviation has reached about 15%.As the electric potential difference between the second microchannel plate and the anode increases,the maximum linear output voltage of the anode shows fluctuating changes.When the electric potential difference between the second microchannel plate and the anode is around 200 V,the linear output voltage of the anode reaches its peak.As the electric potential difference increases,the linear output voltage of the anode begins to fluctuate,reaching the second peak at a electric potential difference of around 500 V.In this article,we investigated the influence of the frequency of pulse input light and the electric potential difference between the second microchannel plate and the anode on the dynamic range of MCP-PMT,and obtained two conclusions through experimental verification:1)As the pulse input frequency increases,the output voltage of MCP-PMT will detach from the linear region earlier.2)As the potential difference between MCP2 and the anode increases,the maximum linear output voltage of MCP-PMT does not simply vary monotonically,but exhibits a constantly fluctuating trend in resistance.On this basis,further exploration was conducted on the factors that constrain the dynamic range of MCP-PMT,namely insufficient wall charge supplementation and interference from space charge effects.When the frequency of the input pulse is high,the constraint on the dynamic range of MCP-PMT is mainly related to the former;when the electric potential difference between the second microchannel plate and the anode increases,due to the complex situation of a large number of secondary electrons transferring between the plates to the anode,the dynamic range will be affected by the space charge effect and cannot be directly proportional to the electric field strength.
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