| Gas Electron Multiplier(GEM) is one of new position sensitive gas detectors developed by CERN in the past few years.Its basic component is the kapton foil coated with copper on double sides,and etched with high density of micro holes.In working condition,high voltage is applied between the two copper sides,the electrons can be avalanched inside the holes,leading the amplification of primary ionization.Since GEM has a lot of excellent performance,such as high counting rate,radiation hardness,small material budget,high space and time resolution,convenient readouts,detection of different rays by using various converters et al,it shows potential applications in many fields.To meet the need of Beijing Synchrotron Radiation Facility(BSRF) to two-dimensional detectors,a big program supported by Chinese Academy of Sciences was initialized to develop the two-dimensional position sensitive X-ray GEM detector satisfied the diffraction and the dispersion experiments requirement for BSRF.A triple-GEM prototype with sensitive area of 100×100mm2,constructed with standard foils from CERN,was studied at first.The basic performance was tested.The best energy resolution measured with full energy photo-electron peak(5.gKeV) of 55Fe X-ray source is 20.2%,and effective gain is over 104.In order to explore two-dimentional imaging capacity of GEM,images were obtained by using 8×8mm2 induced pads and a digital data acquisition system with 96 channels.In order to realize a good spatial resolution,the GEM prototype based on two-dimensional PCB strips and anolog readout were designed and constructed.A device of foil stretching with tension sensors has been set up and a readout electronics system was also developed.Through the test of two kinds of strip pitchs,the correct two-dimentional strip pitch and self-trigger of GEM were choosen,and its two-dimentional spatial resolution were about 110μm and 79μm respectively.The effect of the sum of the voltages applied on the three GEM foils on the spatial resolution was studied and position veracity and linearity of GEM was tested.The experiences of GEM based on anode readout and the anolog electronic system were obtained simultaneouslyThe test of performance showed the GEM detector and the readout system owned a pretty good spatial resolution'performance for BSRF. |
