Photoneutron spectrum at Pohang Neutron Facility based on 100-MeV electron linac

Pohang Neutron Facility (PNF) is a pulsed neutron facility based on the 100-MeV electron linear accelerator. It was constructed for nuclear data production in Korea, and it consists of an electron linear accelerator, a water-cooled Ta target with a water moderator and a time-of-flight path with an 11 m length. The 100-MeV electron linac uses a thermionic RF-gun, an alpha magnet, four quadrupole magnets, two SLAC-type accelerating sections, a quadrupole triplet, and a beam-analyzing magnet. In the design of a water-cooled Ta target, we used the Monte Carlo simulation codes, EGS4 and MCNP version 4B. The neutron energy spectrum is measured for different water levels inside the moderator and compared with the calculation results by the Monte Carlo N-Particle (MCNP) transport code system