TY - JOUR

T1 - Optimization of the Guide Design of MIRACLES, the Neutron Time-of-Flight Backscattering Spectrometer at the European Spallation Source

AU - Villacorta, Felix J.

AU - Rodriguez, Damian Martin

AU - Bertelsen, Mads

AU - Bordallo, Heloisa N.

PY - 2022/3/1

Y1 - 2022/3/1

N2 - To boost the science case of MIRACLES, the time-of-flight backscattering spectrometer at the European Spallation Source (ESS), an optimized neutron guide system, is proposed. This systematic study resulted in an enhancement in the transport of cold neutrons, compared with the previous conceptual design, with wavelengths ranging from lambda = 2 angstrom to 20 angstrom along the 162.5-m distance from source to sample. This maintained the undisturbed main focus of the instrument, viz, to carry out quasielastic and inelastic neutron scattering (QENS and INS) experiments on a large dynamic range and for both energy-gain and energy-loss sides. To improve the collection of cold neutrons from the source and direct them to the sample position, the vertical geometry was adjusted to an adapted version of a ballistic elliptical profile. Its horizontal geometry was conceived to: (i) keep the high-resolution performance of the instrument, and (ii) minimize the background originating from fast and thermal neutrons. To comply with the first requirement, a narrow guide section at the pulse shaping chopper position has been implemented. To fulfil the second, a curved guide segment has been chosen to suppress neutrons with wavelengths lambda < 2 angstrom. Subsequent tailoring of the phase space provided an efficient transport of cold neutrons along the beamline to reach a 3 x 3 cm(2) sample. Finally, additional calculations were performed to present a potential upgrade, with the exchange of the final segment, to focus on samples of approximately 1 x 1 cm(2); the proposal anticipates a flux increase of 70% in this 1 cm(2) sample area.

AB - To boost the science case of MIRACLES, the time-of-flight backscattering spectrometer at the European Spallation Source (ESS), an optimized neutron guide system, is proposed. This systematic study resulted in an enhancement in the transport of cold neutrons, compared with the previous conceptual design, with wavelengths ranging from lambda = 2 angstrom to 20 angstrom along the 162.5-m distance from source to sample. This maintained the undisturbed main focus of the instrument, viz, to carry out quasielastic and inelastic neutron scattering (QENS and INS) experiments on a large dynamic range and for both energy-gain and energy-loss sides. To improve the collection of cold neutrons from the source and direct them to the sample position, the vertical geometry was adjusted to an adapted version of a ballistic elliptical profile. Its horizontal geometry was conceived to: (i) keep the high-resolution performance of the instrument, and (ii) minimize the background originating from fast and thermal neutrons. To comply with the first requirement, a narrow guide section at the pulse shaping chopper position has been implemented. To fulfil the second, a curved guide segment has been chosen to suppress neutrons with wavelengths lambda < 2 angstrom. Subsequent tailoring of the phase space provided an efficient transport of cold neutrons along the beamline to reach a 3 x 3 cm(2) sample. Finally, additional calculations were performed to present a potential upgrade, with the exchange of the final segment, to focus on samples of approximately 1 x 1 cm(2); the proposal anticipates a flux increase of 70% in this 1 cm(2) sample area.

KW - neutron optics

KW - neutron instrumentation

KW - European Spallation Source

KW - BEAM

KW - SCATTERING

KW - INSTRUMENT

KW - MODERATORS

KW - DYNAMICS

KW - PROPOSAL

KW - COLD

U2 - 10.3390/qubs6010003

DO - 10.3390/qubs6010003

M3 - Journal article

VL - 6

JO - Quantum Beam Science

JF - Quantum Beam Science

SN - 2412-382X

IS - 1

M1 - 3

ER -