On the Possibility of a Significant Increase in the Storage Time of Ultracold Neutrons in Traps Coated with a Liquid Helium Film

It is shown that rough inner walls of a trap of ultracold neutrons can be coated with a superfluid helium film much thicker than the depth of penetration of ultracold neutrons into helium. This coating should reduce the rate of loss of ultracold neutrons caused by absorption in the walls of the trap by orders of magnitude. It is demonstrated that triangular roughness is more efficient than rectangular for the reduction of the rate of loss of ultracold neutrons. Triangular roughness is more easily implemented technically and such diffraction gratings are fabricated industrially. Other methods are proposed to increase the thickness of the protective helium film.

Automated summary

The rough inner walls of a trap for ultracold neutrons can be coated with a superfluid helium film to significantly reduce neutron loss rates. Triangular roughness is more effective than rectangular, easier to implement, and diffraction gratings with triangular roughness are industrially fabricated. Other methods are also proposed to increase the thickness of the protective helium film.