Magnetic trapping offers the possibility for a new technique to measure the neutron lifetime which is free from the systematic errors which have limited previous measurements. We have successufully demonstrated the magnetic trapping of neutrons. The trapping region is filled with superfluid 4 He, which is used to load neutrons into the trap and as a scintillator to detect their decay. This work verifies the theoretical predictions of the loading process and the technique of magnetic trapping of neutrons. Further refinement of this method should lead to improved precision in the measurement of the beta-decay lifetime of the neutron.
Axial confinement is provided by two solenoids with the same current sense.
Radial confinement is provided by four current bars parallel to the beam axis which together form a quadrupolar field. This defines a cylindrical confinement region centered around the beam axis. In order to magnetically trap a neutron, its total energy must be reduced to less than the trapping potential while it is located inside the confinement region. The superthermal technique for UCN production, as proposed by Golub and Pendlebury, satisfies this requirement. Neutrons close to this energy can scatter to near rest by emission of a single phonon.