Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Log inSign up
Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Blog
Job Board
Q3AS

© 2026 Aqora Quantum S.A.S.

TermsPrivacyLegal Notice

Journal of Experimental and Theoretical Physics Letters

On the depolarization of ultracold neutrons in traps

Yu. N. Pokotilovski

Published Aug 1, 2002• 7 citations
Publisher

Abstract

Mechanisms of the depolarization of ultracold neutrons in traps reflecting from the trap wall are considered. One is due to neutron spin-flip elastic or quasielastic incoherent scattering from protons of surface hydrogen contaminations. According to the second one, significant depolarization may take place because of a sudden change in the neutron trajectory on reflection from the wall when the neutron moves even at large adiabaticity parameters in nonuniform magnetic field.

DOI
10.1134/1.1514753

Related papers

Quasielastic neutron scattering by diffusive adsorbed hydrogen as a possible cause of the energy spreading of ultracold neutrons during long storage in traps

Yu. N. Pokotilovskiǐ

Small cooling and heating of ultracold neutrons during long storage in traps have been observed in recent experiments. It is shown that quasielastic neutron scattering due to the diffusive motion of hydrogen at the surface of adsorbed hydrogenous contaminants on the surface may be a possible cause of the spreading of the energy of ultracold neutrons during long storage in traps.

Journal of Experimental and Theoretical Physics Letters•Jan 1, 1999•3 citations

The interaction of UCN with a magnetic field

V. K. Ignatovich, G.B. Pontecorvo

Abstract In this chapter the storage of neutrons in magnetic traps will be considered, as well as issues of UCN polarization and methods of analysing it, and also methods of UCN spin reversal. Magnetic traps have the advantage that no absorption or inelastic scattering exists in them within the range of thermal energies. There are, however, certain peculiarities that must be taken into account in estimating the UCN storage time in these traps. The magnetic field in a trap is extremely inhomogeneous and can confine neutrons within a restricted region of space only in the case of a certain neutron spin projection on to the field direction. When the spin direction changes, and in an inhomogeneous field it is sure to undergo changes, the magnetic ‘walls’ win stop being walls and a neutron will leave the trap with ease. It is noteworthy that a spin flip is most probable when the neutron is as far as possible from the ‘magnetic wall’, and not when it impinges upon the ‘wall’.

•Oct 11, 1990•0 citations

Spin-flip loss in magnetic traps for ultracold neutrons

A. Steyerl, E. Gutsmiedl

A particle with spin and magnetic-dipole moment can be trapped in certain suitable magnetic-field configurations only as long as its spin remains aligned with the field direction as it moves through the trap. Here, we extend earlier analyses of spin-flip probabilities, which lead to storage loss for ultracold neutrons, and present arguments indicating that some of the earlier results should be multiplied by a factor of two.

Physical Review C•Oct 13, 2020•1 citation

Heating ultracold neutrons by acoustic oscillations of the trap walls

А. С. Герасимов, V. K. Ignatovich, M.V. Kazarnovskii

The heating of ultracold neutrons by acoustic oscillation of the trap walls is theoretically examined. The probability of changing the neutron energy during collisions with oscillating walls are calculated classically and quantum mechanically. Kinetic equations describing the dependence on residence of the total number of neutrons in the trap are derived and solved. (tr-auth)

•Aug 1, 1973•0 citations

Resonance capture by hydrogenous impurities and losses of ultracold neutrons in solid material traps

G.S. Danilov

The capture of trapped ultracold neutrons (UCNs) by closed hydrogenous impurities within a solid coating of the trap is discussed as a possible cause of observed anomalously large losses of UCNs in solid material UCN traps. Then significant losses of UCNs arise only if resonances occur in the UCN-impurity scattering amplitude. For a large size impurity, higher partial waves in the UCN-impurity interaction are important, and they are taken into account in the present paper. The method of the calculation is applicable to irregular shape impurities as well. A small distortion of an impurity shape, if it splits the resonance, can increase the UCN losses by a few times. UCN losses in the beryllium trap are calculated assuming they are due to the UCN capture by ice spherical impurities within the coating of the trap walls. Both s- and p-wave resonances contribute significantly to the UCN losses considered. As an example, observed anomalous large UCN losses are achieved if the average radius of the impurity is about 600 Angstroms and the impurity density is about 3*10^{14}/cm^3. A distortion of the spherical shape of the impurity could increase the UCN losses and therefore decrease the impurity density.

arXiv:0903.0458•Mar 3, 2009•0 citations

First ever storage of ultracold neutrons in a magnetic trap made of permanent magnets

В. Ф. Ежов, A. Z. Andreev, A.A. Glushkov +13 more

Further improvement in the accuracy of any neutron lifetime experiment by means of ultracold neutrons (UCN) in material bottles is limited due to unavoidable systematic effects when the UCN are reflected from the walls. However, such effects can be excluded in principle if magnetic trapping of UCN is used. The storage of UCN in a small magnetic trap made of permanent magnets was demonstrated for the first time ever. The measured storage time in this feasibility study was (882 ± 16) s. At this level of accuracy no depolarization was observed.

Journal of Research of the National Institute of Standards and Technology•Jul 1, 2005•23 citations
Mechanisms of the depolarization of ultracold neutrons in traps reflecting from the trap wall are considered. One is due to neutron spin-flip elastic or quasielastic incoherent scattering from protons of surface hydrogen contaminations. According to the second one, significant depolarization may take place because of a sudden change in the neutron trajectory on reflection from the wall when the neutron moves even at large adiabaticity parameters in nonuniform magnetic field.
Abstract In this chapter the storage of neutrons in magnetic traps will be considered, as well as issues of UCN polarization and methods of analysing it, and also methods of UCN spin reversal. Magnetic traps have the advantage that no absorption or inelastic scattering exists in them within the range of thermal energies. There are, however, certain peculiarities that must be taken into account in estimating the UCN storage time in these traps. The magnetic field in a trap is extremely inhomogeneous and can confine neutrons within a restricted region of space only in the case of a certain neutron spin projection on to the field direction. When the spin direction changes, and in an inhomogeneous field it is sure to undergo changes, the magnetic ‘walls’ win stop being walls and a neutron will leave the trap with ease. It is noteworthy that a spin flip is most probable when the neutron is as far as possible from the ‘magnetic wall’, and not when it impinges upon the ‘wall’.
The capture of trapped ultracold neutrons (UCNs) by closed hydrogenous impurities within a solid coating of the trap is discussed as a possible cause of observed anomalously large losses of UCNs in solid material UCN traps. Then significant losses of UCNs arise only if resonances occur in the UCN-impurity scattering amplitude. For a large size impurity, higher partial waves in the UCN-impurity interaction are important, and they are taken into account in the present paper. The method of the calculation is applicable to irregular shape impurities as well. A small distortion of an impurity shape, if it splits the resonance, can increase the UCN losses by a few times. UCN losses in the beryllium trap are calculated assuming they are due to the UCN capture by ice spherical impurities within the coating of the trap walls. Both s- and p-wave resonances contribute significantly to the UCN losses considered. As an example, observed anomalous large UCN losses are achieved if the average radius of the impurity is about 600 Angstroms and the impurity density is about 3*10^{14}/cm^3. A distortion of the spherical shape of the impurity could increase the UCN losses and therefore decrease the impurity density.
Further improvement in the accuracy of any neutron lifetime experiment by means of ultracold neutrons (UCN) in material bottles is limited due to unavoidable systematic effects when the UCN are reflected from the walls. However, such effects can be excluded in principle if magnetic trapping of UCN is used. The storage of UCN in a small magnetic trap made of permanent magnets was demonstrated for the first time ever. The measured storage time in this feasibility study was (882 ± 16) s. At this level of accuracy no depolarization was observed.