Introducing the inverted-geometry time-of-flight backscattering instrument, MARS at SINQTregenna-Piggott, Philip L.W.; Juranyi, Fanni; Allenspach, Peter
doi: 10.1080/10238160802180393pmid: N/A
The design and performance of the new inverted-geometry time-of-flight backscattering instrument, Mica Analyzer high Resolution inverted time-of-flight backscattering Spectrometer (MARS) located at SINQ, at the Paul Scherrer Institut, is described. The spectrometer boasts high resolution over a large neutron energy transfer range, reaching 1 µeV at the elastic line. The foremost distinguishing feature is the moveable analyzer banks, allowing resolution matching between the primary and secondary instrument, thus achieving optimal intensity. A wide Q-range is obtained by selecting different mica analyzer reflections, rendering MARS a highly versatile spectrometer with applications foreseen across many branches of the physical and biological sciences.
Reduction of data from inverted-geometry time-of-flight instrumentsTregenna-Piggott, Philip L.W.; Juranyi, Fanni; Christiansen, Peter; Willendrup, Peter K.; Lefmann, Kim
doi: 10.1080/10238160802348446pmid: N/A
The validity of differing prescriptions for the reduction of data collected on inverted-geometry time-of-flight instruments has been investigated by means of Monte-Carlo ray-tracing simulations for a virtual instrument closely resembling OSIRIS at the ISIS facility and experimental measurements on the newly commissioned instrument, MARS at SINQ, PSI. In both cases, the prescription recently set out by Dorner [Bruno Dorner, J. Neutron Res. 13, 267–274 (2005)] yields the correct scattering function.
Use of 2π-PSD systems for quasielastic neutron time-of-flight experimentsLechner, R.E.
doi: 10.1080/10238160601045565pmid: N/A
Very-large-area detector systems for low-energy-transfer time-of-flight spectrometers are discussed. Four different kinds of linear position-sensitive detector arrays with spherical- or cylindrical-zone geometries are considered. A non-uniform sample–detector distance is involved, varying by up to 40% for cylindrical symmetry using 5 m long linear position-sensitive detectors (PSDs). Integration over large solid-angle regions causes practical consequences for data treatment, but no serious problems for spectrometer performance. We demonstrate that energy-resolution function, PWR optimization, and duration of spectral periods are essentially not deteriorated. Consequences for the normalization of measured neutron scattering data and mechanical detector implementation are discussed.
Primary spectrometer neutron optics simulations for a new cold neutron backscattering spectrometerBordallo, H.N.; Frick, B.; Schober, H.; Seydel, T.
doi: 10.1080/10238160802401344pmid: N/A
The future new cold neutron backscattering spectrometer IN16B at the Institut Laue-Langevin is being designed to maintain the extremely high energy resolution of the existing backscattering spectrometer IN16 (approximately 0.4 µeV full width at half maximum in a standard configuration). Simultaneously, a phase space transformation (PST) device will significantly increase the flux at the sample position at the expense of an acceptably more divergent incoming beam. A wide wavelength band (Δλ/λ ≈ 10%) has to be offered to the PST device in order to achieve a significant flux gain by a factor of at least 4. Thus, IN16B will have to be located at the end of a cold neutron guide, whilst the present IN16 is located at a side position along a guide. In order to optimize the layout of individual components and to estimate the instrument performance, the Monte Carlo simulation programs McStas and VITESS have been used. McStas and VITESS offer a general framework to compose virtual neutron scattering instruments and support both reactor and spallation neutron sources. In this paper, we report on studies to optimize the neutron delivery towards the PST device, with an emphasis on results from McStas. The simulations of IN16B were performed for two different hypothetical guide end positions, namely a shorter guide with 58Ni coating and existing gaps and instruments upstream, and a longer dedicated guide with a ballistic layout and supermirror coating. For the simulations, different models of the available cold neutron moderator sources have been taken into account. A neutron velocity selector and an elliptical focus guide were optimized for the purposes of IN16B.