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Technische Universität München> Technische Universität MünchenHelmholtz-Zentrum Hereon> Helmholtz-Zentrum Hereon
Forschungszentrum Jülich> Forschungszentrum Jülich

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Lichtenbergstr.1
85748 Garching

SPHERES

Backscattering spectrometer

This instrument is focussed on cold neutrons. All parameters given here are valid during the current operation of FRM II. Please get in touch with the instrument team well in advance for all further details (length of experiment etc.).

Insrumentscheme SPHERES 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 the investigation of 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 it unavoidable to use a primary beam deflector and a duty-cycle chopper.

At SPHERES, these two functions are both realised by a chopper that bears 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 setup with 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 to access 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 investigation of 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 tunneling [7].

Raw histograms are accumulated on an equidistant ω grid. A script driven program, SLAW [8], is provided to normalise the raw counts, to perform optional binning, and to deliver S(q,ω) in a variety of output formats so that users are not bound to any specific data analysis program. In data fitting, it is critically important to convolute theoretical models with the measured resolution function in an efficient and numerically stable way. We strive to support best practice through our FRIDA package [9].

[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).
[8] Wuttke, J.: SLAW – a neutron histogram to scattering law converter, https://jugit.fz-juelich.de/mlz/spheres/slaw
[9] Wuttke, J.: FRIDA – fast reliable interactive data analysis, https://jugit.fz-juelich.de/mlz/frida

Typical Applications
  • Hyperfine splitting
  • Molecular reorientations and rotational tunneling
  • Dynamic signature of phase transitions
  • Hydrogen diffusion
  • Liquid dynamics
  • Polymer relaxation
  • Protein motion
Sample Environment
  • Cryofurnace 3…700 K
  • Dilution inset 100 mK
  • Furnace up to 1700 K
Technical Data
Primary beam
  • Neutron guide: NL6-S
  • Neutron wavelength: 6.27 Å
  • Neutron energy: 2.08 meV
Main parameters
  • Resolution FWHM: 0.62 – 0.66 µeV
  • Dynamic range: ± 31 µeV
  • Q range: 0.2 – 1.8 Å-1
  • Illuminated area: 40 × 30 mm2
Choppers
  • PST chopper frequency 83 Hz
  • background chopper frequency
    • 83 Hz: high intensity setting
    • 41.5 Hz: high signal-to-noise setting
Detectors
  • 10 3He counter tubes
  • 4 small angle 3He front-window counters (out of backscattering)
  • 6 position-sensitive diffraction detector tubes (covering scattering angles of about 30° to 120°)

Instrument Scientists

Dr. Michaela Zamponi
Phone: +49 (0)89 158860-793
E-Mail: m.zamponi@fz-juelich.de

Dr. Marcella Berg
Phone: +49 (0)89 158860-676
E-Mail: ma.berg@fz-juelich.de

SPHERES
Phone: +49 (0)89 158860-522

Operated by

JCNS

Publications

Find the latest publications regarding SPHERES in our publication database iMPULSE:

impulse.mlz-garching.de

Citation of the instrument

Heinz Maier-Leibnitz Zentrum. (2015). SPHERES: Backscattering spectrometer. Journal of large-scale research facilities, 1, A30. http://dx.doi.org/10.17815/jlsrf-1-38

For citation please always include the DOI.

Gallery

SPHERES
SPHERES
© Andreas Heddergott/ TU Muenchen
Resolution at SPHERES
Resolution at SPHERES

Figure 1: A resolution of 0.65 ueV, a dynamic range of ±31 µeV, and a signal-to-noise ratio of 1000 : 1 or better are routinely achieved in user experiments [5].

MLZ is a cooperation between:

Technische Universität München> Technische Universität MünchenHelmholtz-Zentrum Hereon> Helmholtz-Zentrum Hereon
Forschungszentrum Jülich> Forschungszentrum Jülich

MLZ is a member of:

LENS> LENSERF-AISBL> ERF-AISBL

MLZ on social media: