Study of the neutron guide design of the 4SEASONS spectrometer at J-PARC

We report the result of the analytical and numerical studies to optimize the design of the neutron guide system for 4SEASONS, one of the chopper spectrometers for the spallation neutron facility in Japan Proton Accelerator Research Complex (J-PARC). We propose semi-analytical methods to design the shape of guide tube and the m-value of the supermirror based on an elliptic geometry. With thus obtained geometry of the guide, we demonstrate that sufficient intensity gain at the energy range of 4SEASONS can be obtained.