Generation of a transversely uniform high-current proton beam with variable central energy

This paper presents a method for obtaining a transversely uniform distribution of a high-current proton beam with energies ranging from 1 to 13 MeV. A beam distribution with low nonuniformity, specifically below 10%, can enhance the performance of power semiconductor devices once their essential components have been irradiated by the beam. Beam uniformity can be achieved using methods such as scattering, beam expansion, small-spot scanning, or the nonlinear magnet. To achieve a transversely uniform beam with minimal energy spread from an existing high-current linear accelerator (linac), a combination of the nonlinear magnet method and beam expansion method has been selected. To produce a beam with an energy of less than 3 MeV and a reduced energy spread, the energy of the 3 MeV beam accelerated by the radio frequency quadrupole (RFQ) is lowered by an aluminum energy degrader. The 3 MeV beam can pass through the drift tube linac (DTL) cavity with high transmission even when the RF power supplied to the DTL cavity is significantly attenuated. The transverse nonuniformities in the diameters of 149 mm and 92 mm for the sample have been measured to be 9.8% and 6.2% for 3 MeV irradiation. In contrast, the simulation results using the hard-edge model show values of 3.6% and 1.7%.