Magnetic lenses for neutron beams

Abstract

Purpose

To provide information on magnetic lens design principles for neutron beam focussing and to characterize the efficiency of these devices.

Design/methodology/approach

Magnetostatic and neutron optical computations are presented for permanent magnet and electromagnetic hexapole lenses for neutron beam focusing. The numerical results are verified by magnetic and neutron beam measurements.

Findings

Neutron lenses built from brick‐shaped permanent magnets approximating the six‐pole Halbach structure yield relatively high field constant for a relatively small useful diameter. Electromagnets are weaker, but allow field constant adjustment.

Research limitations/implications

The main limitation of both presented solutions resides in the difficulty of obtaining high magnetic flux densities. Superconducting coils in hexapole configuration can overcome this limitation.

Practical implications

The magnetic lenses can be used for beam focusing in scattering neutron instruments. The focused beam is also polarized.

Originality/value

Analytical formulae are supplied for the neutron path calculation in a six‐pole magnetic field. An electromagnet design with permanent magnet flux enforcement is provided.

Citation

Füzi, J. (2005), "Magnetic lenses for neutron beams", COMPEL - The international journal for computation and mathematics in electrical and electronic engineering, Vol. 24 No. 2, pp. 628-638. https://doi.org/10.1108/03321640510586231