The Study Of The Micromegas Detector

In the beginning of the 1990 decade, Micromegas detector had been developed by Y.Giomataris and G. Charpak in Saclay group of French. It belongs to MPGD(Micropattern Gaseous Detectors). Micromegas detector is a very asymmetric two-parallel plate avalanche chamber. It uses a thin metal grid to separate the drift region where the primary electrons are produced from the amplification region (-100μm thick) where they are multiplied. It has shown great promise for handling high data rates with a rather low-cost structure. It can provide very good gas gain, space resolution and time resolution with small dead spaces, too. So it is widely used in any branch of nuclear physics experiments, the medicine imaging, and the like.In our group, we developed the first mciromegas detector in China. The performance of Micromegas is studied by the 3D simulation and the experiments carefully.We combine the Maxwell field calculation software and Garfield to simulate the performance of Micromegas in detail. We simulated the electronic field of 3D Micromegas detector structure using ansoft Maxwell. We calculate the electron drift velocity, the diffusion coefficients with the electric field in different Ar/CO2 gas mixtures. We can understand the property of Micromegas by the simulation very well. The results of simulations provide important information on the study of Micromegas structure.The main things which were done by me and will be the contents of my PhD thesis are the following:□Constructing and studying a micormegas prototype with the different active area and different wire mesh. Testing the count plateau, gas gain and energy resolution of prototype with different mixture of argon-carbon dioxide via different voltage. The best energy resolution got by us with 55Fe X-ray source (5.9KeV) is 16.7%.The count plateau can reaches around 150v; Testing the micromegas detector with the active area of 50X50mm2 in the low and normal press using the 239Pu a source; The time resolution is better than 14.8ns, and the detecting The detecting efficiency is over 97% using cosmic rays.□In brief, we have got wonderful results at same experimental condition through separating the conversion gap from an amplification gap by stainless steel micromesh or Ni foil which can be found wide use in the neutron detection and beam monitor.