FSANS

FSANS is a small angle neutron scattering (SANS) instrument. It employs a technique distinct from that of the Yellow Submarine SANS, complementing the size range studied by the latter. This enables the probing structures at length scales ranging from 2.5 to 600 nm.

When a sample is irradiated with a neutron beam, the scattering pattern of neutrons at small angles — detected with a two-dimensional neutron detector — provides insights into the properties of the examined material. For example, it facilitates the calculation of nanoparticle size, determination of their orientation, or assessment of the quality of their surface throughout the examined volume of a sample.

The FSANS instrument has a broad spectrum of applications, encompassing studies of defects and precipitates in materials, alloy segregations, nanostructures of surfactant and colloid solutions, polymers, proteins, characteristics of biological membranes, ferromagnetics, magnetic correlations, and more.

In addition to its general application in small angle neutron scattering, the FSANS instrument has been specifically optimized to facilitate non-destructive archaeological investigations. When SANS is applied to ceramics, the resulting scattering pattern can be utilized to determine the average orientation and degree of elongation (anisotropy) of nano-sized particles, such as clay minerals, and pores. The orientation and elongation of these scattering entities are indicative of the forces exerted during the vessel-forming process. Consequently, through the examination of orientation patterns, it becomes feasible to infer the forming technique employed in the vessel’s production in a non-destructive manner.

This full-page space is for the instrument long description. It can be longer then 1 page here and additional images, all the technical parameters and descriptions can be placed here which are on the current BNC website’s instrument pages.

The FSANS instrument is a time-of-flight type diffractometer, covering a momentum transfer or Q-range from 0.001 to 0.266 Å^-1, enabling the study of structures at corresponding length scales ranging from 2.5 to 600 nm.

The SANS method, and consequently the FSANS instrument, have a wide range of applications, encompassing the study of defects and precipitates in materials, alloy segregations, nanostructures of surfactant and colloid solutions, polymers, proteins, characteristics of biological membranes, ferromagnetics, magnetic correlations, and more.

The instrument is situated on the lower segment of the curved neutron guide No.10/3, constructed with m = 2 supermirrors. It operates with a beam time structure defined by three choppers: a counter-rotating pair of pulse definition choppers, and a wavelength limiting and frame overlap chopper. The available wavelength range spans from 2 to 14 Å. The width of wavelength uncertainty, Δλ, can be set by selecting the pulse definition chopper window to either 0.3 Å with at 8° opening (better resolution mode) or 0.75 Å with 20° opening (higher intensity mode), respectively. The collimation and maximum sample-to-detector distances are 3.7 and 4.3 m, respectively. The instrument’s configuration is illustrated in Figure 1. The detector allows for both vertical and horizontal movement, as well as bidirectional tilting of the detector arm, providing a high level of flexibility compared to standard settings.

Figure 1. Layout of the FSANS diffractometer

Samples ranging from several millimetres to several tens of centimetres in diameter can be accomodated at the sample position. The beam size is adjustable, ranging from 1 to 27 mm in diameter.

Scattered neutrons are captured by a 256×256 pixel two-dimensional position-sensitive detector, with a pixel measuring 0.7×0.7 mm², filled with ³He-CF₄ gas mixture. Data acquisition is carried out in event recording mode. The detector’s vertical and horizontal movement, along with bidirectional tilting of the detector arm, provide a notable degree of flexibility compared to the default settings.

The spectrum measured on the No.10/3 cold neutron beamline of the Budapest Research Reactor (representing the intensity distribution transmitted from the cold source spectrum by the neutron guides) at the location of the FSANS instrument is depicted in Figure 2.

Figure 2. The spectrum measured on the 10/3 cold neutron beamline of the Budapest Research Reactor at the FSANS instrument’s position

The following table presents the key characteristics of the FSANS instrument. Default configuration: the detector is positioned in-line with the direction of the direct neutron beam.

FSANS characteristics (default configuration)		Details
Beam	Cold neutron guide No. 10/3	Cross section of the neutron guide at the exit: 25 x 25 mm2
Monochromation	Chopper system with three choppers	1st and 2nd Choppers: counter-rotating pair of pulse definition choppers. Openings: 8°@0°and 20°@90°. Maximum rotation speed: 3000 rot/min. Disc diameter: 400 mm.  3rd Chopper: wavelength limiting and frame overlap chopper. Openings: 42°@0°and 42°@180°. Maximum rotation speed: 1500 rot/min. Disc diameter: 400 mm.
Detector	2D position sensitive	Type: 3He-CF4 gas detector Size: 200×200 mm2 Pixel size: 0.7×0.7 mm2 Beam-stop diameters: 4, 8, 10, 14, 20 mm, with x, y motion.
Collimation length	3.7 m	The future option for adjusting collimation and focusing mirror installation is permitted. Various slit sizes at both ends of the collimator are available with automatic motion control. Slit diameters at the sample size: 1, 10, 20, 27 mm and a rectangular slit: 3 mm x 19 mm.
Sample to detector distance	1 to 4.3 m Vacuumed flight path between sample and detector	Detector arm with automatic motion control:  – front end horizontal translation: ± 100 mm;  – front end vertical translation: ± 200 mm;  – back end horizontal translation: ± 700 mm;  – back end vertical rotation: – 7° … + 10°. Flight tube: – length: 3500 mm, composed of 4 detachable sections; – inner diameter: 280 mm; – inner diameter at the inlet side: 70 mm.
Wavelength range	2 – 14 Å	The maximum of the Maxwell-Boltzmann spectra is between 2 and 3 Å. Wavelength uncertainty: 0.3 – 0.74 Å
Scattering vector range	0.0006 – 0.2663 Å-1	Scattering vector resolution: 0.00005 Å-1
Sample environment		Multipurpose sample changer under development

Figure 3 displays an example of a small angle scattering measurement. Data were collected using both the FSANS and the SANS-YS instruments. The samples under study were multi-wall carbon nanotubes/epoxy polymer composites. The SANS measurements facilitated the characterization of the nanostructure of the various composites at a broad length-scale, which was subsequently correlated with their electrical conductivity properties [1].

Figure 3. SANS measurements on CNT/epoxy composites conducted with the FSANS and YS-SANS instruments

In addition to its general application in small angle neutron scattering, the FSANS instrument has been retailored to facilitate non-destructive archaeological investigations. When SANS is applied to ceramics, the resulting scattering pattern can provide valuable insights into the average orientation and degree of elongation (anisotropy) of nano-sized particles (Figure 4) such as clay minerals, and pores. These characteristics are closely linked to the forces experienced during the vessel forming process (Figure 5a). Thus, by analysing the orientation, it becomes possible to infer the forming technique used to produce the vessel, in a non-destructive way (Figure 5, b and c). This information to deduce the forming technique used to create the vessel, in a non-destructive way. This information proves particularly beneficial in cases where the vessel’s macro-structural features, indicative of the primary forming technique, are obscured by secondary techniques like polishing, burnishing, smoothing, painting, glazing, or by environmental impacts like soil erosion. Furthermore, SANS enables non-destructive differentiation between techniques that may exhibit similar macroscopic characteristics, such as wheel-throwing and wheel-shaping. [2]

Figure 4. Two-dimensional anisotropic SANS scattering patterns: (a) and (b) are 2D models, (c) is the measured data pattern. θ is the tilting angle, α/β ratio is the elongation ratio

Figure 5. (a) Examples of sample preparation techniques. (b) Archaeological samples prepared for SANS measurement. (c) Measurement setup on the FSANS instrument

[1] Boukheir, S ; Len, A ; Fuzi, J ; Kenderesi, V ; Achour, ME; Eber, N ; Costa, LC ; Oueriagli, A ; Outzourhit, A; Fractal structure and temperature-dependent electrical study of carbon nanotubes/epoxy polymer composites; SPECTROSCOPY LETTERS 50 : 4 pp. 183-188. , 6 p. (2017)

[2] Len, A. ; Bajnok, K.; Füzi, J.: Small-Angle Neutron Scattering for Cultural Heritage Studies; In: D’Amico, S; Venuti, V (szerk.) Handbook of Cultural Heritage Analysis; Cham, Svájc : Springer-Verlag (2022) 2,256 p. pp. 189-210. , 22 p.