Conceptual design of the time-of-flight backscattering spectrometer, MIRACLES, at the European Spallation Source

Research output: Contribution to journalArticle


In this work, we present the conceptual design of the backscattering time-of-flight spectrometer MIRACLES approved for construction at the long-pulse European Spallation Source (ESS). MIRACLES's unparalleled combination of variable resolution, high flux, extended energy, and momentum transfer (0.2-6 Å-1) ranges will open new avenues for neutron backscattering spectroscopy. Its remarkable flexibility can be attributed to 3 key elements: the long-pulse time structure and low repetition rate of the ESS neutron source, the chopper cascade that tailors the moderator pulse in the primary part of the spectrometer, and the bent Si(111) analyzer crystals arranged in a near-backscattering geometry in the secondary part of the spectrometer. Analytical calculations combined with instrument Monte-Carlo simulations show that the instrument will provide a variable elastic energy resolution, δ(Latin small letter h with stroke ω), between 2 and 32 μeV, when using a wavelength of λ ≈ 6.267 Å (Si(111)-reflection), with an energy transfer range, Latin small letter h with stroke ω, centered at the elastic line from -600 to +600 μeV. In addition, when selecting λ ≈ 2.08 Å (i.e., the Si(333)-reflection), δ(Latin small letter h with stroke ω) can be relaxed to 300 μeV and Latin small letter h with stroke ω from about 10 meV in energy gain to ca -40 meV in energy loss. Finally, the dynamic wavelength range of MIRACLES, approximately 1.8 Å, can be shifted within the interval of 2-20 Å to allow the measurement of low-energy inelastic excitations.


  • N. Tsapatsaris
  • R. E. Lechner
  • M. Markó
  • H. N. Bordallo
External organisations
  • University of Copenhagen
  • Hungarian Academy of Sciences
Research areas and keywords

Subject classification (UKÄ) – MANDATORY

  • Accelerator Physics and Instrumentation
Original languageEnglish
Article number085118
JournalReview of Scientific Instruments
Issue number8
Publication statusPublished - 2016 Aug 1
Publication categoryResearch