Development of an Adiabatic RF Neutron Spin Flipper at the China Spallation Neutron Source

A new prototype adiabatic RF-flipper was recently developed at the China Spallation Neutron Source. The prototype device was calibrated at the test beamline BL-20 over a wavelength range of 0.6 Å to 5.5 Å, and achieved a flipping efficiency of 97% for neutron wavelengths above 4 Å. During the development of the adiabatic RF-flipper, finite element method and spin transformation simulations were applied to precisely determine the magnetic field configuration and neutron spin-flip efficiency. This work demonstrates the design and optimization of the adiabatic RF-flipper for a specific neutron beamline, where the dependence of the flipping efficiency on neutron wavelength can be analyzed through simulation and numerical calculation for pulsed neutron beams.