Imaging Linearity Modeling and Optimization of Capacitive Division Image Readout (C-DIR) for Microchannel Plate Imaging Detectors

A 3-D lumped parameter circuit model based on the nodal analysis to simulate signal propagation and position response characteristics of capacitive division image readout (C-DIR) is proposed. The current pulses, charge collection efficiency, and position reconstruction patterns are calculated for different electrical parameters (charge division capacitor C-c, perimeter capacitor C-p, diagonal capacitor C-d, electrode parasitic capacitor C-s, and the sheet resistance of the resistive layer R-Ge), and their influence on imaging linearity is investigated. The simulation results show that R-Ge affects the amplitude, pulsewidth, and polarity of the current pulse in the C-DIR. The sheet resistance of the resistive layer needs to be larger than 10 MQ for the charge to be efficiently collected by the readout electronics. Several capacitance ratios (C-c/C-p, C-c/C-s, and C-c/C-d) mainly affect the imaging linearity. It has been found that to obtain good detector imaging performance, C-c/C-p should be less than 0.01, C-c/C-s should be larger than 100, and C-c/C-d should be larger than 10, and when RGe is larger than 10 Mg, the imaging nonlinearity (rms) can be less than 1%. The reliability of the simulation results was verified by experimental measurements of a prototype C-DIR detector designed by ourselves. An optimized imaging performance with imaging nonlinearity (rms) of 2.18% was achieved.

Automated summary

A 3-D lumped parameter circuit model based on nodal analysis is proposed to simulate the signal propagation and position response characteristics of capacitive division image readout (C-DIR). The influence of various electrical parameters on imaging linearity is investigated through calculation of current pulses, charge collection efficiency, and position reconstruction patterns. Simulation results show that the sheet resistance of the resistive layer and the capacitance ratios have significant effects on imaging linearity. Experimental measurements of a prototype C-DIR detector verify the reliability of the simulation results, achieving an optimized imaging performance with an imaging nonlinearity (rms) of 2.18%.