Εξειδίκευση τύπου :	Άρθρο σε επιστημονικό περιοδικό
Τίτλος:	Cold versus thermal neutron source: assessment of performance of the KWS-2 SANS diffractometer of the Jülich Centre for Neutron Science at the FRM II reactor
Δημιουργός/Συγγραφέας:	Radulescu, Aurel Biehl, Ralf [EL] Παπαγιαννόπουλος, Αριστείδης[EN] Papagiannopoulos, Aristeidis
Ημερομηνία:	2025-10-01
Γλώσσα:	Αγγλικά
ISSN:	0021-8898
DOI:	10.1107/S1600576725006491
Άλλο:	41064422
Περίληψη:	The small-angle neutron scattering (SANS) diffractometer KWS-2 of the Jülich Centre for Neutron Science at the Heinz Maier-Leibnitz Zentrum, Garching, Germany, is a high-flux instrument based on the combination of a specially developed neutron guide system, which allows delivery of a high neutron intensity for a wide wavelength range λ between 2.8 and 20 Å to the instrument, and a versatile velocity selector, which allows an easy choice of wavelength spread Δλ/λ depending on whether the specific scientific goal is either improved resolution, i.e. Δλ/λ = 10%, or high intensity, i.e. Δλ/λ = 20%. Here we report an evaluation of KWS-2 performance by measurements and McStas simulations under the condition that only the thermal neutron source (TNS) is available at the FRM II reactor. According to the simulations, a flux decrease by a factor of 2.5 for λ = 2.8-3 Å and by a factor of 10 for λ ≥ 4.5 Å is expected if the reactor is operated only with the TNS compared with the established performance with cold neutrons provided by the cold neutron source. The flux decrease in TNS operation can be mitigated for λ ≥ 4.5 Å by using a low-resolution velocity selector which provides Δλ/λ = 20% for standard positioning and Δλ/λ = 35% when tilted at an angle ξi = -10° to the beam axis. According to measurements, this degradation of resolution for increasing intensity does not seem to be critical for the structural characterization of small biological morphologies, which would be one of the most investigated topics if only thermal neutrons were available at the FRM II. However, ordering effects in the scattering characteristics of lamellar soft or biophysical systems are barely observable when the resolution is relaxed to Δλ/λ ≥ 20%, which defines the performance limits of the experimental approach. Furthermore, by using MgF2 focusing lenses when working with large samples, an intensity gain on the sample of up to 12-fold is achieved while keeping the same Q min resolution as with the standard pinhole mode, restoring the flux loss expected with thermal neutrons for λ ≥ 7 Å.
Τίτλος πηγής δημοσίευσης:	Journal of applied crystallography
Τόμος/Κεφάλαιο:	58
Τεύχος:	Pt 5
Θεματική Κατηγορία:	[EL] Φυσική και θεωρητική χημεία[EN] Physical and theoretical chemistry [EL] Ηλεκτρική μηχανική. Ηλεκτρονική. Πυρινική μηχανικη[EN] Electrical engineering. Electronics. Nuclear engineering
Λέξεις-Κλειδιά:	McStas simulation SANS neutron focusing lenses neutron sources protein structure small-angle neutron scattering
Κάτοχος πνευματικών δικαιωμάτων:	© Aurel Radulescu et al. 2025
Όροι και προϋποθέσεις δικαιωμάτων:	Published under CC BY license.
Ηλεκτρονική διεύθυνση στον εκδότη (link):	https://doi.org/10.1107/S1600576725006491
Εμφανίζεται στις συλλογές:	Ινστιτούτο Θεωρητικής και Φυσικής Χημείας (ΙΘΦΧ) - Επιστημονικό έργο