SPHERES

This instrument is focussed on cold neutrons. Therefore, please carefully check the “Technical data WITHOUT cold source” section. Deviating parameters are in bold. The instrument team is happy to answer any further questions!

Insrumentscheme SPHERES

SPHERES (SPectrometer for High Energy RESolution) is a third-generation backscattering instrument with focussing optics and a phase-space-transform (PST) chopper [1]. It is a versatile spectrometer for investigating atomic and molecular dynamics on a GHz scale. The necessary filtering of neutron energies is achieved by Bragg reflection from perfect monochromator and analyser crystals under angles close to 180°.

The backscattering geometry makes using a primary beam deflector and a duty-cycle chopper unavoidable. At SPHERES, these two functions are realised by a chopper bearing deflector crystals on its circumference. This leads to a particularly compact spectrometer layout so that full use can be made of the focussing neutron guide. As an additional advantage, the fast motion of the deflector crystals achieves a phase-space transform of the primary spectrum, thereby enhancing the flux at the sample.

The redesign of PST chopper and focussing guide in recent years led to a more than doubled intensity. The newly installed background chopper also allows for a low background set-up with a significantly increased signal-to-noise ratio by eliminating every second pulse, albeit at the cost of intensity.

SPHERES enables investigations on a broad range of scientific topics. It is, in particular, sensitive to the incoherent scattering from hydrogen and allows access to dynamic processes up to a timescale of a few ns. Typical applications include, for example, relaxation processes in soft matter materials like polymers [2] and nanocomposites, dynamics in biological systems [3] or hydrogen diffusion in various systems like ionic conductors and fuel cells [4]. Furthermore, the high resolution of the spectrometer allows for the investigation of the dynamics of viscous liquids and water in confined geometry [5]. Other important applications are hyperfine splitting in magnetic materials [6] or reorientational motions and rotational tunnelling [7].

[1] Wuttke et al., Rev. Sci. Instrum. 83, 075109 (2012).
[2] Zorn et al., Macromolecules 53, 6731 (2020).
[3] Schirò et al., Phys. Rev. Lett. 126, 088102 (2021).
[4] Appel et al., RSC Adv., 9, 37768 (2019).
[5] Soininen et al., J. Chem. Phys. 145, 234503 (2016).
[6] Chatterji et al., J. Phys.: Condens. Matter 31, 025801 (2019).
[7] Rok et al., CrystEngComm 22, 6811 (2020).