Tasks & Partners

Sub-task 19.2.1: Large solid angle polarisation analysers.

The extension of the capacity of neutron polarimetry towards large solid angle polarisation analysis represents a difficult challenge. We are planning to take advantage of the latest tremendous progress achieved in polarizing neutron mirrors and in effective polarization of thermal neutron beams by neutron spin filters. The latter particularly allows for the neutron polarization analysis for short wavelengths, 0.5-1 Å, which are required for studies of high-energy neutron exchanges. Problems related to the mechanical stability of optical cells will be overcome by the modular (honeycomb-like) design of large solid angle neutron spin filters.

Sub-task 19.2.2: Large solid angle magnetic environment friendly spin-handling devices.

New types of large solid angle spin-handling devices, like spin flippers, precession coils and guide fields, particularly featuring low level scattered magnetic fields, which are relatively harmless for the operation of 3He neutron spin filters, will be developed. The SNS Polarised Neutron group will actively contribute to this task as non-European collaborator.

Sub-task 19.3.1: Correction elements for high energy resolution.

NSE spectrometers deliver the highest energy resolution achievable in neutron scattering.
However, to access extremely slow dynamics even higher energy resolution is required. We will
develop precise correction elements, which allow the necessary equalizing of the magnetic field integral provided by super-conducting coils, for wide neutron beams to achieve a reasonable intensity after the scattering and to push the achievable neutron spin-echo beyond 1 μs.

We will investigate the machining errors that occurred during the realization of the oblique cuts design and also develop a new type of correction elements with the “normal” straight cuts in combination with extra current loops to compensate for finite cut width.

Sub-task 19.3.2: Development of a large-(Q, )-range inelastic neutron scattering spectrometer based on a combination of time-of-flight and Larmor labelling (TOFLAR).

The idea of TOFLAR is to develop a large-(Q, )-range inelastic neutron scattering spectrometer
applying Larmor modulation for scattered, and time-of-flight for incoming wavelength
measurement (or vice-versa), which in principle yields quasi- and inelastic spectra. Since there is no selection of neutron wavelengths for either the incoming or scattered beam, there is no a priori selection of the energy transfer range and resolution and therefore much of the available flux is used.

Sub-task 19.4.1: Larmor labelling with rotating magnetic fields and time-gradient magnetic

fields. In the case of elastic scattering, the Larmor labelling method called SESANS enables precise angular measurements of momentum transfer even with rather non-collimated neutron beams. We will exploit opportunities offered by recently developed method of Larmor labelling with rotating magnetic fields and time-gradient magnetic fields and develop new high-performance spin turners that feature smaller amount of the material in the beam, lower operational electrical current and large length allowing for very high tilt angles for neutron beams of a large cross-section. Similarly to the NSE spectrometer, the SESANS setup requires.

Sub-task 19.4.2: SANS and reflectometry with MIEZE.

The main advantage of the MIEZE technique is the possibility to measure samples in a high
magnetic field or macroscopically magnetized samples. We will combine the MIEZE principle with
the SANS and reflectometry methods allowing for inelastic and spatially resolved inelastic measurements at very small momentum transfer and incorporate MIEZE systems in existing
instruments.

Sub-task 19.4.3: Correction elements for high momentum resolution.

The field integral corrections elements for the SESANS setup, allowing for the significant
enhancement of the angular resolution will be developed in the frame of this task.

Sub-task 19.5.1: NRSE coils: high fields, new field geometries.

We will develop large solid angle NRSE coils allowing for the parallel data acquisition in a wide range of the momentum transfer and thus for a tremendous gain in the data acquisition rate, an extended to the shorter wavelengths operational range and new geometries for higher tilt angles.

Sub-task 19.5.1: NRSE coils with minimized amount of material in the beam.

We will also develop new NRSE coils with reduced thickness of material (current loops) in the
neutron beam.

In the frame of this task we are planning to exploit some new possibilities for new developments offering by polarised neutrons:

Sub-task 19.6.1: Ultra-Small-Angle Polarised Neutron Scattering (USANSPOL)

We plan to extend the meanwhile well-established USANS technique to polarized neutrons using
the spin-dependent neutron refraction by the passage through the prismatically shaped magnet field in combination with the extremely narrow width of perfect crystal Bragg reflections, that should open new fields of research and applications for the study of magnetic materials.

Sub-task 19.6.2: Development of an ultra-flexible neutron magnetic resonator

An ultra-flexible neutron magnetic resonator (Drabkin type) shall be developed whose
implementation in neutron scattering instruments should allow an almost instantaneous variation of key parameters, as incident and final neutron energy, spectral width of incoming beam, energy
resolution, etc. by purely electronic means.

Sub-task 19.6.3: Polarised neutron technique for measurements of three/many point correlation functions

We propose to develop the principle of the method allowing one to measure the three-point
correlation function (CF). Using the NRSE technique we can split the initial neutron wave into four waves, so that in the precession path of the first NSE arm these four neutron waves will produce phase shifts corresponding to three different distances: these neutron waves probe the sample simultaneously on three length scales. The theoretical study and computer simulations of
measurements of the triplet CF using combination of FW-NRSE and SESANS will be performed
for hard sphere solution, which pair CF was studied recently by SESANS.

The Polarised Neutron work package relies heavily on simulations of magnetic systems using the
commercial software (e.g. ANSYS or RADIA) and on Monte-Carlo simulations with polarized
neutrons using simulation packages McStas and VITESS. Because of complexity of such
simulations, most partners will not become expert users and should be supported in these activities. Such support will be provided by a dedicated scientist hired in the frame of this Work Package, who will also develop new modules for simulations of the polarized neutron instruments or their components.