Simulation of Penning ion source with optimized beam extraction system for tagged neutron tube

摘要

The magnetic field structure of the Penning ion source has been optimized with the use of permanent magnets. The ion source has been designed for small sealed tagged neutron tube. By using CST Studio Suite, the magnetic field profile inside the ion source was simulated and a variety of magnetic system was designed to improve the magnetic field uniformity of the Penning ion source and to increase the neutron yield. And the simulation results were compared with the experimental data to verify the correctness of the model. A new type of ion focusing system was devised by using the characteristics of conducing magnetic and consolidating magnetic of different metallic materials. There is more uniform magnetic field distribution and less material for the structure of 6-ring magnets placed outer anode than the structure of cylindrical magnet below the cathode. Stainless steel is selected as the material of the new extraction system after comparing the magnetic relative permeability of several materials. The new system has obvious focusing effect on the ion beam. It is also easy to obtain a small beam spot with 1 mm radius suitable for the tagged neutron tube and the extraction electrode voltage gets lower than original voltage. The results can provide reference for the improvement of the tagged neutron tube.