Conceptual design of target station and neutron scattering spectrometers for the Chinese spallation neutron source

We report the recent progress on the conceptual design of the target station and neutron scattering spectrometers for the Chinese Spallation Neutron Source (CSNS). The CSNS target station will be constructed with three parts: tungsten targets cooled by heavy water, Be/Fe reflectors and Fe/high-density-iron-aggregate-concrete shields. There will be 3 WING moderators: water (300 K), liquid methane (100 K) and liquid hydrogen (20 K), and 18 horizontal neutron channels for neutron scattering spectrometers. The Monte Carlo simulation shows that the optimized ratio of height to width of the target cross-section is -1:2.5. With a nuclear power of 100 kW, the pulsed neutron flux is 2.4×10¹⁶ cm^-2·s^-1 for a 40 mm × 100 mm × 10 mm × 40 target stack. The emitted heat is about 47 kJ/s, the target temperature is somewhat higher than 90°C with a normal cooling efficiency, and the strain should be lower than 0.2 mm. Initially 5 typical spectrometers are chosen to be constructed, including a high intensity powder diffractometer, a high resolution powder diffractometer, a small angle scattering spectrometer, a reflectometer and a direct geometry inelastic neutron scattering spectrometer. These spectrometers can cover more than 80% of the neutron scattering applications.