Recent Improvement of the Signal-to-Noise Ratio on the Fermi Chopper Spectrometer 4SEASONS

We report recent progress in improvement of the signal-to-noise (S/N) ratio on the Fermi chopper spectrometer 4SEASONS at the Japan Proton Accelerator Research Complex (J-PARC). We could much reduce the background scattering by installing vanes made of B4C resin inside the vacuum scattering chamber and polyethylene plates behind the detector bank. The improved S/N ratio enables a measurement with a short time or with a small sample.