Measurement of the neutron lifetime in a magnetic storage ring

Measurement of the neutron lifetime by counting trapped protons in a cold neutron beam

“…The deviation from the 1/v law in the 6 Li(n,t) 4 He cross section has been shown to be less than 0.01 % [32] and changes in the neutron beam due to decay-in-flight and residual gas interaction are less than 0.001 %. The cancelation allows this technique to make full use of the broad neutron energy spectrum from the reactor cold source.…”

“…[36,37] The target in the neutron monitor consists of a thin (≈ 0.4 mm) 50 mm-diameter singlecrystal wafer of silicon with an evaporated deposit of 6 LiF. This deposit is thin enough that the neutron fluence rate is only slightly attenuated, and the products from the 6 Li(n,t) 4 He reaction suffer negligible scattering or energy loss in passing through it. The alpha particles and tritons produced by the neutron absorption reactions in 6 Li are detected by four surface barrier detectors, each of which has a solid angle defined by a diamond-turned precision aperture, as shown in Fig.…”

Electromagnetic traps for charged and neutral particles

“…But due to the relatively low flux of neutrons in the acceptable velocity range, their number was too low to make relevant measurements with it. In a recent experiment [28] at a new neutron beam with a flux improved by a factor 40 we could observe neutrons up to 90 min, i.e. roughly 6 times the decay time of the neutron due to radioactive decay.…”

Magnetic trapping of ultracold neutrons

“…This technique was first discussed by Vladimirskiȋ in 1961 [9], just two years after Zeldovich first discussed material storage [10]. Since that time there have been several experiments to store neutrons magnetically with varying degrees of success [11][12][13][14].…”

“…were stored in a sextupole magnetic storage ring analogous to the storage rings used at particle accelerators [12,14]. Magnetic field gradients reflect neutrons at a glancing incidence, storing neutrons in certain trajectories.…”