The Research Of GEM Detector And Its Readout System

GEM Detector is a new kind of micro-pattern gas detector, and has great prospect in particle physics experiment and low energy X-ray imaging system. We are developing a triple GEM, and testing the basic performances such as leakage current, noise, effective gain and energy resolution. From our test, the leakage current and noise are both low, effective gain could reach 105, and energy resolution is about 24% with X-ray at 5.9 KeV.GEM detector has many advantages. One of them is the flexible readout methods. Based on the differences of their working principles, the existing readout methods could be divided into four classes. Their working principles and structures are introduced. According to the advantages and disadvantages of these resdout methods, we are investigating the pixel readout of GEM detector with an array of filed effect transistors (FETs) using PCB technology. This readout method has advantages of simple manufacture, flexible parameters, low cost and can provide us primary data for the future readout method based on thick-film technology and TFT. From our test, the dynamic range could reach 7.3×104, INL is less than 0.324%, sensitivity is 2.54 mV/pC, and readout could be in real time (30 frames/sec). The test methods and test results are analyzed in this paper.After accumulating enough knowledge about GEM detector and FET switches array, using our lab's DAQ system, we are developing a GEM detector imaging system based on FET switches array readout method. The imaging experiment with 55Fe and micro-focus X-ray generator is done. And the spacial resolution, the contrast sensitivity, the variance between readout units, the relationship between system output and X-ray generator working current are analyzed in this paper.