Radiography and tomography with polarized neutrons

High resolution neutron imaging capabilities at BOA beamline at Paul Scherrer Institut

“…The precession of neutron spins in the magnetic fields can be used to map the distribution of these fields across the field of view [13,14]. That mapping can be very useful for studies where magnetic probes cannot be used, for example, in the investigation of magnetic fields within various objects which can be penetrated by neutrons.…”

“…At the same time the developments of novel neutron imaging techniques partially compensate the lack of spatial resolution as they can provide unique information in some cases. For example, dark field imaging or grating interferometry [10][11][12], or imaging of magnetic fields with polarized neutron beams [13,14], extend the contrast of neutron imaging experiments beyond the conventional radiography modes where the contrast is provided by the difference of the attenuation coefficient. The crucial parameters of a neutron beamline facility in such experiments are the intensity of neutron flux, its spectrum, the degree of collimation, gamma content and, in some cases, the degree of polarization.…”

Imaging of dynamic magnetic fields with spin-polarized neutron beams

“…The unique ability of neutrons to penetrate materials opaque to other types of radiation, combined with their ability to interact with a magnetic field through the neutron spin precession, makes neutrons an excellent probe for remotely studying magnetic field distributions, even internally within solid objects. Various techniques utilizing polarized neutrons have been developed for the spatially resolved investigation of magnetic fields [1][2][3][4][5][6][7][8][9][10][11][12][13][14]. One of these techniques correlates the variation of neutron intensity with the magnetic field strength and direction, allowing effective magnetic field imaging [2,3,[5][6][7][8][9][10].…”

“…Various techniques utilizing polarized neutrons have been developed for the spatially resolved investigation of magnetic fields [1][2][3][4][5][6][7][8][9][10][11][12][13][14]. One of these techniques correlates the variation of neutron intensity with the magnetic field strength and direction, allowing effective magnetic field imaging [2,3,[5][6][7][8][9][10]. Also interferometric and diffraction methods have been available for a number of years, where the dependence of the real part of the refractive index on the magnetic field strength can be exploited [1,4,11,12] including methods utilizing spin echo [13,14].…”

“…However the latter techniques operate with neutron beams of low intensity caused by all the necessary beam conditioning, and further, some of them require spatial scanning through the sample, and therefore provide very limited imaging statistics, but with the tradeoff of providing very good spatial resolution. The alternative approach combines the conventional neutron imaging technique (whereby the two-dimensional neutron flux intensity distribution is measured after the sample) with the neutron spin analysis [5][6][7][8][9][10]. Magnetic fields within relatively large areas (tens of centimeters in linear dimension) can be studied by this technique without spatial scanning.…”