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DREAM

The Diffraction Resolved by Energy and Angle Measurements (DREAM) powder diffractometer will be constructed at European Spallation Source (ESS) as an in-kind contribution led by Forschungszentrum Jülich (Germany) in collaboration with Laboratoire Léon Brillouin (France) [1,2].

The science case of DREAM instrument is focused on the structure determination of complex materials with large unit cells, studies of new compounds with an interplay of magnetism and superconductivity, nanostructures, metal organic frameworks, thermoelectrics, hydrogen storage and catalysis materials. The capabilities of DREAM to perform fast in-situ and small sample measurements will the serve ever-growing needs of various scientific communities.

DREAM-1The layout of the DREAM instrument with the full detector coverage.
Copyright: Forschungszentrum Jülich

Those capabilities are enabled by combination of thermal and cold fluxes in a bi-spectral instrument concept. The broad neutron bandwidth will include both thermal and cold neutrons at their peak intensities, providing at full detector coverage a Q-range of 0.01 – 25 Å–1 in a single frame, which is ideally suited for diffraction studies on multiple length scales.

The design of DREAM utilizes the long pulse and unpreceded peak brightness of ESS to provide a flexible choice between high resolution and high intensity. The estimated highest resolution in the backscattering detector is Δd ~ 0.0003Å will set a new world record in neutron diffraction. The pulse shaping chopper consisting of two fast counter-rotating disks will allow a seamless change between the high resolution and high intensity modes of operation.

The new 2D position sensitive 10B detectors will cover with high efficiency a large solid angle (initial coverage of 1.86 sr and 5.12 sr in the full coverage), and further enable neutron time-of-flight Laue single-crystal diffraction measurements. The future upgrades will include dedicated SANS detector, neutron polarization in forward scattering and dedicated high-pressure station. The full potential of DREAM will be realized through a new approach to the data analysis, which is based on 2D Rietveld refinements of the angular- and wavelength-dispersive diffraction data [3].

The DREAM construction proposal was accepted in 2014 [4]. In the beginning of 2017 the preliminary design review at ESS has set the initial scope and budget for the construction of the instrument.

DREAM-1Copyright: Forschungszentrum Jülich

Simulations of 2D neutron diffraction pattern of Na2Ca3Al2F14 powder for DREAM instrument with complete detector coverage (left panel). The right panel shows resolution for various pulse widths.

DREAM Team:

Forschungszentrum Jülich (DE): Mikhail Feygenson, Werner Schweika, Peter Harbott, Andreas Poqué, Anja Schwaab

Laboratoire Léon Brillouin (FR): Florence Porcher, Sylvain Desert, Burkhard Annighöfer

References and Links:

[1] DREAM publication

[2] ESS highlight of DREAM

[3] 2D Rietveld refinement

[4] DREAM instrument proposal

Contact Information:

Mikhail Feygenson
Werner Schweika


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