First Multilayer-type Neutron Interferometry Measurements of Gases at J-PARC

What is it about?

This study reports the first application of a newly developed measurement system to determine the coherent scattering lengths (bc) of gaseous samples (^3He and ^4He) using a multilayer-type neutron interferometer at J-PARC. While conventional interferometry studies have typically used silicon-crystal interferometers and monochromatic neutrons supplied from reactors, our group developed a multilayer-based neutron interferometer and utilize pulsed neutrons from the J-PARC accelerator. Through 10-minute cycle time-of-flight measurements, we observed significant phase shifts induced by the helium gas samples. This establishes a definitive proof of principle for this methodology and allows us to clarify the specific experimental issues that must be resolved for high-precision experiments.

Featured Image

Photo by Logan Voss on Unsplash

Photo by Logan Voss on Unsplash

Why is it important?

Determining the precise coherent scattering lengths of light nuclei is vital for modern nuclear physics. These values serve as a crucial benchmark for testing advanced phenomenological nuclear models and chiral effective field theories, which attempt to describe the nuclear forces, including three-nucleon forces. Despite their importance, a long-standing mystery persists: past measurements using conventional interferometers show discrepancies for helium isotopes (^3He and ^4He). To resolve these puzzles, a completely new and independent experimental approach is required. This paper lays the essential foundation for a novel methodology utilizing pulsed cold neutrons. By overcoming the limitations of previous experiments, this ongoing project aims to achieve a relative precision of 10^{−3}, providing the data needed to improve nuclear theories.