3D Simulation Study of Electric Field and Electron Trajectories in Gas Electron Multiplier

The distributions of 3D electric field and the electron trajectories of double bowl structure gas electron multiplier(GEM)are simulated based on the finite element method.The electric field and electron trajectories of GEM for different geometric sizes and electrical parameters have been investigated,including external and internal diameters(D and d),Kapton foil thicknesses(T),the GEM voltage(Vgem:the voltage difference between the two copper electrodes on both sides of the GEM Kapton foil),the drift electric field(Ed),and the induct electric field(Ei).Moreover,electron transparencies for different parameters are calculated at the same time.It shows that,D,T and Vgem have great effects on the electric field inside the GEM hole while there is no influence of d,Ed and Ei on the electric field.Only the D,d,Ed and Vgem can influence the electron transparency,the electron transparencies of other parameters are 35.26%.In addition,the influences of(D/P)2 and Eh(the estimated electric field inside the GEM hole)on the electron trajectories have been researched.And it indicates that the geometry transparency and the electric field around the GEM hole is decisive to the electron transparency.