PKUNIFTY: A neutron imaging facility based on an RFQ accelerator

A neutron imaging facility, PKUNIFTY, based on a radio frequency quadrupole (RFQ) accelerator-driven compact neutron source, presently under construction at the Peking University, is described. It consists of a deuteron linear accelerator, a neutron target–moderator–reflector assembly, and a thermal neutron imaging system. Neutrons are generated via the deuteron–beryllium reaction with an expected fast-neutron yield of 3×1012 n/s. The thermal neutron flux on the imaging plane is 5×105 n/cm2/s at a nominal L/D ratio of 50, and the L/D ratio can be selectable over a range of 25–200. The corresponding n/γ ratio is close to or higher than 1×1010 n/cm2/Sv. The field of view is 20 cm×20 cm at 2 m downstream of the collimator entrance aperture where the thermal neutron flux uniformity is better than 7%. The effective Cd ratio can be tuned by using a light chopper and neutron time-of-flight technique without excessive sacrifice of the thermal neutron flux.