A new Frisch-grid ionization chamber has been built to explore the appropriate choice of Frisch-grid. Detailed studies of the relationship between grid geometries and detector performance have been performed with an $$^{241}$$ 241 Am source. This paper describes and compares the energy resolution of ionization chambers with parallel-wire and mesh grids of different grid parameters. Some specific recommendations for grid selection are provided based on the data currently available. To obtain optimal energy resolution, the operating voltage of the chamber must satisfy the condition of minimum electron collection on the grid with distinct geometries and parameters, respectively. Since there is no established theory applicable to both types of grids, we have devised a careful simulation procedure incorporating the COMSOL and Garfield++ codes to search for the conditions of the minimum electron collection on the grid. The simulation results fit the experimental data well, suggesting that this simulation method successfully predicts the suitable voltage setting when using a mesh grid or parallel wires grid as the shielding electrode.
The grid electrode of the grid ionization chamber (GIC) is devoted to eliminating the dependence of the anode pulse amplitude on the initial position and orientation of the ionization. The traditional methods of grid production require cumbersome processes and advanced instruments. In this paper, a bonded stainless steel woven wire mesh (SSWWM) grid electrode manufacturing method is proposed. Compared with the traditional grid electrode, the SSWWM grid features the advantages of simple fabrication, low cost, and high mechanical strength. The energy resolutions of the 40-mesh, 60-mesh and 80-mesh SSWWM grids and orthogonal mesh grid realized by the traditional wire winding method were tested using an 241Am source (around 5.486 MeV). The results show that the optimum energy resolution of the SSWWM and orthogonal mesh grids is approximately 47 keV full width at half-maximum (FWHM). The optimal energy resolutions of the 40-mesh and 60-mesh SSWWM grids are comparable, but the initial operating voltages corresponding to the energy resolution plateau are different, mainly because of the effect of the different geometric parameters of the SSWWM grid on the electron transmittance. A simulation program was used to study the electron transmittance of the SSWWM grid. The simulation results are in agreement with the experimental results, indicating that the simulation program can be used as a reference for the selection of the geometric parameters of the SSWWM grid.
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