The Proton Radiation Effects Facility (PREF) aiming for the displacement damage effect research was proposed by XTIPC (Xinjiang Technical Institute of Physics and Chemistry, Chinese Academy of Sciences) in 2018. The facility was designed and constructed by IMP (Institute of Modern Physics, Chinese Academy of Sciences). The beam commissioning of PREF had been started since August to September of 2023. Four types of instruments, scintillation screen, Faraday cup, scintillator and ionization chamber are implemented for the proton beam profile, intensity, position, efficiency, spill structure. With the beam instruments, the machine reached nearly 95% slow extraction efficiency for all energies from 10 to 60 MeV, 5$\times10^{10}$ particle per second (ppp), 2$\times$2 cm² up to 20$\times$20 cm² scanning area.

Providing 10 to 60 MeV proton beams, the PREF (Proton Radiation Effects Facility) is dedicated to the displacement damage effect experiments. The slow extracted beams from the synchrotron are delivered to two experimental terminals, which required the flux as constant as possible. To characterize the slow extraction parameters, scintillators and ionization chambers are equipped in the transport line and the terminals. The frequency response reveals the major influencing factor, power supply ripples. The duty factor reached over 90% shows the high slow extraction quality of the new accelerator.