title: Prismatic analyser concept for neutron spectrometers.
abstract: Developments in modern neutron spectroscopy have led to typical sample sizes decreasing from few cm to several mm in diameter samples. We demonstrate how small samples together with the right choice of analyser and detector components makes distance collimation an important concept in crystal analyser spectrometers. We further show that this opens new possibilities where neutrons with different energies are reflected by the same analyser but counted in different detectors, thus improving both energy resolution and total count rate compared to conventional spectrometers. The technique can readily be combined with advanced focussing geometries and with multiplexing instrument designs. We present a combination of simulations and data showing three different energies simultaneously reflected from one analyser. Experiments were performed on a cold triple axis instrument and on a prototype inverse geometry Time-of-flight spectrometer installed at PSI, Switzerland, and shows excellent agreement with the predictions. Typical improvements will be 2.0 times finer resolution and a factor of 1.9 in flux gain compared to a focussing Rowland geometry, or of 3.3 times finer resolution and a factor of 2.4 in flux gain compared to a single flat analyser slab.
authors.affiliation: Nano Science Center, Niels Bohr Institute, University of Copenhagen, DK-2100 Copenhagen Ø, Denmark.
authors.forename: Jonas O
authors.initials: JO
authors.lastname: Birk
authors.affiliation: Laboratory for Neutron Scattering and Imaging, Paul Scherrer Institute, CH-5232 Villigen PSI, Switzerland.
authors.forename: Márton
authors.initials: M
authors.lastname: Markó
authors.affiliation: Laboratory for Quantum Magnetism, École Polytechnique Fédérale de Lausanne (EPFL), CH-1015 Lausanne, Switzerland.
authors.forename: Paul G
authors.initials: PG
authors.lastname: Freeman
authors.affiliation: Nano Science Center, Niels Bohr Institute, University of Copenhagen, DK-2100 Copenhagen Ø, Denmark.
authors.forename: Johan
authors.initials: J
authors.lastname: Jacobsen
authors.affiliation: Nano Science Center, Niels Bohr Institute, University of Copenhagen, DK-2100 Copenhagen Ø, Denmark.
authors.forename: Rasmus L
authors.initials: RL
authors.lastname: Hansen
authors.affiliation: Institute of Physics, Technical University of Denmark, DK-2800-Kgs. Lyngby, Denmark.
authors.forename: Niels B
authors.initials: NB
authors.lastname: Christensen
authors.affiliation: Laboratory for Neutron Scattering and Imaging, Paul Scherrer Institute, CH-5232 Villigen PSI, Switzerland.
authors.forename: Christof
authors.initials: C
authors.lastname: Niedermayer
authors.affiliation: Laboratory for Neutron Scattering and Imaging, Paul Scherrer Institute, CH-5232 Villigen PSI, Switzerland.
authors.forename: Martin
authors.initials: M
authors.lastname: Månsson
authors.affiliation: Nano Science Center, Niels Bohr Institute, University of Copenhagen, DK-2100 Copenhagen Ø, Denmark.
authors.forename: Henrik M
authors.initials: HM
authors.lastname: Rønnow
authors.affiliation: Nano Science Center, Niels Bohr Institute, University of Copenhagen, DK-2100 Copenhagen Ø, Denmark.
authors.forename: Kim
authors.initials: K
authors.lastname: Lefmann