The characteristic performance test of the microchannel plate photon-counting imaging detector

摘要

The microchannel plate (MCP) photon-counting imaging detector system based on the wedge-strip positionsensitive anode is designed to provide high spatial and temporal resolution as well as stable gain in low-light level imaging application. This paper introduces the general characteristic performances of MCP stack pulse height distribution (PHD) for signal and background events which are useful to judge the operating state of the photon-counting imaging detector. In order to get the suitable gain and high resolution, the factors such as the voltage applied to MCP stack, input current density, incidence light intensity, temperature and so on, are researched, which affect the detector's gain, spatial resolution and background events. The suitable operating state of the MCP detector with gain uniformity and high resolution were determined according to the measurements of the PHD and the image for a Z MCP stack in different conditions. The experiments indicate that the PHD curves and images are changed with different voltages applied to MCP stack, and evidences show that the shape of PHD is quasiGaussian distribution in a saturation state of MCP stack. If the high voltage applied to MCP stack is too high, the background event rate will be high and the uniformity of the image will become bad. In addition to measuring the gain and background noise characteristics of the MCP detector, the maximum count rate which the MCP detector can sustain before its saturation is also determined, we have researched the relationship between the PHD and the input current density with a fixed high voltage, the experimental results shows that the MCP stack will become saturation when the PHDs change from the negative exponential shape to quasi-Gaussian shape with the increasing of the incidence light intensity, however, if the incidence light intensity is further increased, the shape of PHD eventually become wider as well as the image turned to be dim, obviously, the input current density was too large. On the other hand, in order to reduce the background events, the factors affecting the background noise should be known, therefore, the background event rate as a function of operating temperature from the room temperature to 80'C is measured. The results of the experiments show that the background events rate increase with the operating temperature. In this paper, the PHD characteristics of the signal and dark noise are discussed, in order to get the excellent image, it is necessary to control the high voltage applied to MCP stack, input photon count rate and reduce the background noise.