Design of a low-energy proton facility for space radiation effect research based on a compact neutron source

This paper provides the physical design of a low-energy proton irradiation facility for space radiation effect research, based on an existing linear accelerator (linac)-based compact neutron source. The beam requirement of the low-energy proton irradiation consists of a proton flux range of $10^8$–$10^{9}p∕{\mathrm{cm}}^2∕s$ with a nonuniformity of less than 10% in the target diameter area of 2 cm, and optional proton energies of $<1\mathrm{MeV}$ to 13 MeV. Based on the existing high-current proton linac, the flux range and nonuniformity of the proton beam at the target can be achieved by inserting beam apertures, adjusting quadrupole fields to expand the beam size, and decreasing the repetition rate of the beam pulse. To measure the energy distribution of the protons, one CdZnTe detector can be employed. The above approach is performed on the physical design of the low-energy proton facility for the Compact Pulsed Hadron Source at Tsinghua University. The proton flux at the target can be reduced from $6.2\times 10^{14}p∕{\mathrm{cm}}^2∕s$ to $1.2\times 10^8-3.0\times 10^{9}p∕{\mathrm{cm}}^2∕s$, and proton energies of 0.56, 5.0, 8.2, and 10.5 MeV can be obtained separately with the energy degrader (aluminum) thicknesses of 75, 800, 550, and 300 $\mu$m. Irradiation nonuniformity is less than 10%. Energy spread is less than 10% for the proton energy of 3.0, 5.0, 8.2, and 10.5 MeV, except for the low energy of 0.56 MeV.