EP1535288A2

EP1535288A2 - Neutron optical element for the small angle neutron scattering measuring technique

Info

Publication number: EP1535288A2
Application number: EP03750298A
Authority: EP
Inventors: Ferenc Mezei; Daniel Clemens; Lounis Mokrani
Original assignee: Hahn Meitner Institut Berlin GmbH
Current assignee: Hahn Meitner Institut Berlin GmbH
Priority date: 2002-08-25
Filing date: 2003-08-25
Publication date: 2005-06-01
Anticipated expiration: 2023-08-25
Also published as: US7214948B2; ATE360254T1; WO2004021365A2; WO2004021365A3; AU2003269688A1; US20050178972A1; DE10239691A1; EP1535288B1; DE10239691B4; DE50307088D1; JP2005536757A

Abstract

A high measuring resolution along with a large irradiation surface and a high beam intensity are required for structural analyses of material according to the small angle neutron scattering measuring technique. However, with known diaphragm collimators, the necessary beam divergence cannot be reached without an unacceptable loss of intensity. The inventive neutron optical element (1) comprises a plurality of successively arranged pinhole diaphragms embodied as grating diaphragms (7), each grating diaphragm (7) comprising a plurality of diaphragm apertures (14). In this way, the neutron beam is divided into individual beams which are each improved in terms of the convergence thereof. Furthermore, the channels defined by the course of the grating diaphragms (7) by means of respectively identically positioned diaphragm apertures (14) are narrowed according to the convergence cone provided by the structure of the measuring instrument. Simultaneously, all of the partial beams can be focussed onto the detection spot. In order to select monochrome neutrons, the grating diaphragms (7) are positioned on the speed-dependent parabolic paths. In this way, the claimed, neutron optical element does not only function as a high-resolution, focussing collimator, but also as a speed selector. The continuous and cyclic displacement of the grating diaphragms (7) over all of the parabolic paths enables the entire neutron beam to be used. In this way, the inventive neutron optical element can be especially used for pulsed neutron beams.

Description

Neutron optical component for neutron small-angle scattering measurement technology

description

The invention relates to a neutron optical component for neutron small-angle scatter measurement technology with a plurality of perforated diaphragms made of a neutron-absorbing material, each with at least one active aperture, in support elements in the extension of the neutron beam from the neutron source to the measurement sample, the small-angle beam scattering of which is detected by a detector to reduce beam divergence.

Components for guiding, deflecting and specifically influencing a neutron beam, in particular a cold neutron beam, are referred to as neutron optical components. They are used in test setups for neutron small-angle scatter measurement technology. In order to be able to carry out special measurements, the neutrons must have certain properties, for example a certain energy (equivalent to speed), divergence or focusing on the measurement location, which are brought about by the neutron optical components. Small angle neutron scattering (SANS), in which the neutron radiation scattered by the measurement sample due to physical or chemical inhomogeneities is detected by a corresponding measuring instrument in a relatively small angular range as seen from the sample, represents a key technology for structural investigations in the Nanometer range (1 nm to 100 nm) or above (Ultra Small Angle Neutron Scattering USANS). Possible applications for SANS can be found, for example, in biology and medicine, polymer chemistry, materials science, physics, geology or metallurgy. In order to reduce the divergence of a neutron beam, a so-called "collimator" is used as the neutron-optical component in the measuring instrument. Basically, a distinction is made here between a "layer collimator", which is made up of packages of alternating neutron reflecting and neutron absorbing foils, and a "diaphragm collimator" The aperture collimators normally used in SANS are simple aperture diaphragms, which have a central or several aperture openings of 1 cm to 2 cm in diameter arranged on a circular circuit in a disk made of a neutron-absorbing material. These pinholes are mounted in a carrier element and are arranged in the beam path of the neutron beam. They are generally at a distance of between 2 m and 16 m from one another rd in the state of the art, for example in the "LOQ diffractometer" of the English ISIS system (see http://www.isis.rl.ac.uk/largescale/LOQ/images/Loq.gif, as of August 21, 2002) or in SANS spectrometer "Yellow Submarine" (see http://www.iki.kfki.hu/nuclear/bnc/instruments/instr_sans.html, Stand

19.08.2002) was used. A multifunctional collimator system is known from the article “New SANS Instrument at the BER II reactor in Berlin, Germany by U. Keiderling and A. Wiedenmann (Physica B 213 & 214 (1995) pp 895-897), which consists of four rotatable drum sections , which have different neutron-optical components in the shape of a turret. One of them is a pinhole, so that with this known collimator a maximum of four pinholes can be rotated into the neutron beam, only the pinhole at the beginning and end of the measuring instrument are effective. The SANS spectrometer "Yellow Submarine" uses three spaced pinhole diaphragms, all of which are effective. In the LOQ diffractometer, from which the present invention is based as the closest prior art, two pinhole diaphragms are used. On both pin diaphragms several diaphragm openings with different diameters are arranged on a circulating circuit, which can be rotated into the neutron beam if necessary, so that only one diaphragm opening is active at a time. One pinhole is arranged in the beginning, the other in the end region of the extension of the neutron beam between the neutron source and the sample. The divergence of the neutron beam is reduced by only allowing neutrons to pass through the aperture openings. Beyond the apertures, the neutron-absorbing material from which the pinhole diaphragms are made destroys those neutrons whose trajectories do not run in the desired divergence cone. A reduction in the size of the pinhole and / or an increase in the spacing of the effective pinhole from one another does indeed reduce the divergence cone, as a result of which the instrumental resolution of the measuring instrument is improved. However, a reduction in the opening angle of the divergence cone and a reduction in the size of the pinhole aperture are accompanied by a significant reduction in the beam intensity that can be measured behind the aperture system. This means that when the sample is irradiated, the sufficient neutron intensity cannot be achieved with a simultaneously high measurement resolution.

To improve the measurement resolution, the combined reflectometry and small-angle scattering system KWS 3 with focusing mirror is known (see http://www.fz-juelich.de/iff/lnstitute/ism/pictures/poster.jpg, as of August 21, 2002). Here, a toroidal mirror with a plurality of curved mirror layers is used as the focusing neutron optical component, which focuses the neutron beam in several planes through the sample onto a point in the detector plane. However, such a mirror is very complex to manufacture. A pinhole to reduce the beam divergence is arranged in front of the toroidal mirror and has a diaphragm opening that can vary between 1 mm ² and 100 mm ² . By this compared to the known pinhole with aperture in cm ² area of a much smaller aperture, the beam divergence can be improved, but the beam intensity is drastically reduced. Further focusing neutron optical components have refractive lenses, magnetic lenses or curved crystals. The resulting focus for these neutron optical components depends on the neutron speed, which has a disadvantageous effect on their use on measuring instruments that use a broad speed distribution. These are, for example, the neutron instruments working according to the time-of-flight principle, as they mainly work on the neutron sources of the newer generation, the spallation neutron sources. Here it is important to make full use of each pulse. Refractive lenses extend many centimeters along the neutron beam. This leads to loss of intensity for the materials in question. Reflective or refractive neutron-optical components have a disadvantageous effect on the scatter pattern due to their own scattering characteristics, which result because they are usually not ideal to produce.

The neutron beam in continuous and pulsed form has neutrons of different speeds. Due to the equivalence of the speed to the wavelength of the neutrons, neutrons of the same speed can therefore be referred to as "monochrome neutrons". In order to be able to provide only neutrons of a wavelength band, a speed selection is therefore necessary. This is done with a speed selector, we It is known, for example, from the KWS3, which is a neutron-optical component with a rotating drum, along which absorber compartments are arranged with a spiral course. The standing drum is neutron-impermeable because there is no unobstructed view through the material-free channels between the spiral compartments However, neutrons pass through these channels at a suitable speed during rotation, and this known speed selector is relatively complex to produce. Since neutrons are subject to gravity due to their mass, their trajectory is a parabola. Their curvature depends on the flight speed of the neutrons. The flight parabola is therefore a wavelength-selective sorting measure for monochrome neutrons. Fast neutrons have a flat, slow neutrons have a strongly curved trajectory.

Against the background of the prior art explained above, the task for the present invention is seen in developing a generic neutron optical component with pinhole diaphragms in such a way that it achieves a high measurement resolution in the function of an aperture collimator. For this purpose, depending on the beam divergence on the largest possible radiation area on the measurement sample, a sufficiently high radiation intensity must be guaranteed. Furthermore, the neutron-optical component according to the invention should be able to take on further beam-influencing functions, in particular those of beam focusing and speed selection. Use in particular for pulsed neutron beams should also be possible. Despite this multifunctionality, however, the neutron-optical component according to the invention should be relatively simple in its construction and in its technical feasibility. Furthermore, it should not create any disruptive influences on the scatter patterns.

In a neutron optical component for the neutron small-angle scattering measurement technology of the type mentioned at the outset, the solution to this task therefore provides according to the invention that, depending on the required measurement resolution and the extension length of the neutron beam, a number n of pinhole apertures, which are designed as grating diaphragms, ensures the beam guidance, is provided with a variable distance from one another and that each grating diaphragm has a constant number m of closely adjacent diaphragm openings which divide the neutron beam passing through into a number m of partial beams and a size decreasing in the direction of the measurement sample to reduce the divergence of the partial beams have, in each case the diaphragm openings defining a partial beam of all n grating diaphragms being arranged at least in a time interval given by the flight time of monochrome neutrons on their parabolic orbit and all partial beams being focused on the detector.

The neutron-optical component according to the invention has perforated diaphragms in the form of grating diaphragms. A particularly high resolution is achieved when the measurement sample is irradiated due to the aperture openings which are greatly reduced in comparison with known aperture openings and which result in a substantial reduction in the beam divergence. The drastic loss of intensity associated with a simple reduction of an aperture (the measured beam intensity is proportional to the 4th power of the aperture diameter) is avoided, however, by the neutron beam provided by the neutron source being formed by the sieve-like design of the pinhole diaphragms in the form of grating diaphragms with a large variety of small aperture openings is divided into a corresponding number of partial beams. Each partial beam representing its own channel is continuously guided through all of the associated aperture openings on all grating apertures, and its divergence is thereby continuously improved. Due to the sum of all individually improved partial beams, a large irradiation area on the measurement sample is irradiated with great intensity. It is possible to enlarge the illuminated sample area by a factor of 10 to 100 compared to a conventional single-channel system. The intensity of the neutron beam is hardly reduced, the neutrons provided are used well, which is particularly advantageous in the case of a pulsed neutron beam. Due to the many small aperture openings, which advantageously have dimensions in the range from 1 mm to 2 mm and which can be cut with a high manufacturing precision of 0.01 mm to 0.02 mm through the use of highly precise computer-controlled manufacturing techniques (eg laser cutting) , the intensity losses due to the absorption of neutrons in the webs between the apertures are very low held. The dimensioning of the web width still prevents neutron migration between the individual channels.

Furthermore, the individual partial beams are focused on the detector location, so that a focusing collimator is realized with the invention. Focusing is carried out by appropriately guiding the bundle of all individual beam channels toward the focus. The measure for the reduction depends on the convergence cone formed by the entire measuring instrument. This basically determines the entire structure of the collimator according to the invention with regard to the number and spacing of the individual grille shutters and the number, spacing and size of the aperture openings. A change in the divergence cone accordingly also requires a change in the collimator structure. The divergence cone begins with the beam cross section of the neutron beam provided by the neutron source and ends in the ideally point-shaped detector location. The length of the divergence cone is determined by the length of extension between the initial neutron beam and the detector location in the measuring instrument. The measurement sample is positioned in the convergence cone according to the desired radiographic area. The required reduction for the individual diaphragm openings depending on the position of the respective pinhole in the convergence cone can thus be calculated according to the ray set. A computer-aided calculation is helpful when determining parameters.

The number of grating shutters used depends on the path length of the neutron beam in the measuring instrument. For example, twenty lattice screens can be arranged in the beam path in a compactly dimensioned structure (for example 2 m). When selecting the number, it is important to ensure the guidance of the individual partial beams, which is given by the spacing of the aperture openings in the individual lattice apertures and the respective absorption in the surrounding webs. Since there is still a relatively large divergence of the partial beams in the initial region of the neutron beam, adequate beam guidance can advantageously be achieved here by a relatively dense arrangement of the grille shutters can be achieved. With increasing divergence, the distance between the individual grating diaphragms in the direction of the measurement sample can then be increased. Therefore, when implementing the invention, it is advantageous if the distance between the grating diaphragms increases in the direction of the sample. Furthermore, the lattice panels can be designed as a lattice frame with square aperture openings. Such lattice frames, which can consist in particular of the neutron absorbing cadmium, are simple components whose square diaphragm openings in rows and columns are much easier to manufacture than round diaphragm openings. The dimensioning of the required absorbing webs and the reduction of the individual aperture openings in the course of the divergence cone can be calculated and carried out numerically without any problems. With the neutron optical component according to the invention, the measurement resolution of the measuring instrument can thus be freely adjusted over a wide range by a corresponding choice of the number n of grating diaphragms and the number m of diaphragm openings for channel formation.

The neutron-optical component according to the invention, in its function as a focusing collimator, consists of an arrangement of a plurality of grating diaphragms that only allow beam paths that converge on the same location in the detection plane. A specific aperture in each grille aperture is assigned to each channel. The successive row of grating diaphragms then defines the individual channel or the converging course of the individual partial beams into the focus in the detection plane. To generate the individual channels, it is necessary that the grating diaphragms are aligned exactly in the beam path of the neutron beam with regard to their diaphragm openings. This exact alignment of the grille shutters along or for determining the beam path is achieved with the aid of the support elements which hold the grille shutters. With the help of vertical translation units with high positioning accuracy, for example actuators with micrometer screws or piezo actuators, an alignment to 0.01 mm or better possible. The lattice diaphragms or individual diaphragm openings are aligned on the parabolic orbits of the monochrome neutrons characterized by their flight speed, since these are subject to gravity. Every permitted parabolic orbit is traversed only by neutrons of almost the same speed and therefore wavelength. Due to the exact alignment of all diaphragm openings defining a channel or partial beam over the entirety of all grating diaphragms, a narrow wavelength band around the ideal wavelength, which in turn results from the neutron speed, is transmitted through the collimator system. This means that speed selection is also possible with the neutron optical component according to the invention. This works not only as a focusing collimator, but also as a speed selector. The neutron optical component according to the invention thus fulfills two essential functions in SANS measurement technology and is a multifunctional component with great compactness and simplicity in manufacture. Elaborate rotating speed selectors, as are known from the prior art, are not required ,

In the vertical alignment of the grille shutters, a distinction must be made between the static and the dynamic case. In the static case for a continuous neutron beam, speed selection is necessary. In this case, the aperture openings of the grille shutters are permanently aligned on a predetermined parabolic path. The vertical translation units allow the respective grille shutters to be precisely aligned with the conceivable parabolic orbits. Thus, only the neutrons flying on the set parabolic orbit in the entire neutron beam reach the measurement sample. When using neutron beam pulses, however, it is essential to utilize the entire intensity occurring in the pulse as far as possible. This can be achieved through the dynamic fall in the alignment of the aperture openings. In the static case mentioned above, the aperture openings defining a partial beam are all n grating diaphragms are arranged on their parabolic orbit at least in a time interval given by the flight time of monochrome neutrons. Here, the term "at least" is interpreted in the sense of permanent alignment on a single parabolic orbit. In dynamic cases, the grating diaphragms or their apertures traverse a large number of conceivable parabolic orbits. When setting each parabolic orbit, a certain time delay along the neutron flight path can occur in the measuring instrument In the dynamic case, it is therefore advantageous for the neutron-optical component according to the invention if the aperture openings lying on the parabolic path of monochrome neutrons in a time interval given by the flight time of monochrome neutrons in further time intervals given by the flight time of other monochrome neutrons by corresponding local displacement of the grating diaphragms lie on their parabolic orbits. Thus monochrome neutrons of different speeds are collimated and focused. By the selectable setting on different parabolic orbits, which is equivalent to influencing the gravitational force effectively acting on the flying neutrons, the transmitted wavelength bands of the neutron-optical component according to the invention, which also functions as a speed selector, can thus be set in a targeted manner. With a continuous process of the grating diaphragms over the parabolic orbits of all monochrome neutrons appearing in the neutron beam, the selection effects for the speed of the neutrons completely disappear - a gravitational-free system is available - and the neutron optical component becomes a broadband optic, as is required for pulsed neutron sources. The process over all parabolic orbits in the pulsed neutron beam can advantageously be carried out in a continuous, oscillating sequence. Accordingly, it is advantageous if the grille shutters are moved in an oscillating manner between the top and bottom parabolic orbits.

The implementation of prescribed periods of motion for the entire neutron optical component according to the invention with all grating apertures, such as it requires, for example, the situation described below without gravity, can be achieved by an electronically controlled movement of the grille shutters. It is therefore advantageous if the shifting of the grille shutters takes place via a corresponding time control of drive units of the vertical translation units or of support rails holding them. The drive units required for the displacements can be adjusting screws (micrometer screws) moved by controlled servomotors, stepping motor driven adjusting screws, piezoelectric actuators or any other electronically programmable movement system. In order to reduce the acceleration forces that occur, the entire component or the carrier elements of the grille shutters can advantageously be mounted on springs so that its natural frequency is close to the clock frequency. In this case, it is also a task for the electronic control to convert the sinusoidal movements of the oscillating base for the grille shutters into a parabolic movement with constant acceleration during the active phase.

The gravitation effectively acting in the neutron optical component according to the invention is changed by moving the grating diaphragms in the vertical direction with an acceleration A during the neutron passage. After a phase of uniform acceleration, acceleration in the opposite direction takes effect in order to bring the grille shutters back into their starting position. The size of the acceleration A determines the selection sharpness of the desired speed band. It can therefore be advantageous in the case of the neutron-optical component if the grating diaphragms are shifted in time-defined acceleration phases. In the special case A = g (g = gravitational acceleration) there is a speed-independent collimation. A numerical example for the implementation of this principle is explained in more detail below. Gravitation-free collimation for a time of 40 ms is achieved by choosing the acceleration A = g. There is then a "relativistic collimator" in the sense of the principle of general relativity of the motion, that is, the free fall for the neutrons is simulated. In the remaining 20 ms of a 60 ms long period, as is the case for a spallation source pulsed at 16,666 Hz, the grating diaphragms can then be returned to their starting positions by selecting A = -2g. Your starting position, at which the free fall begins, requires a vertically upward starting speed of 0.1962 m / s. After 20 ms, the grille shutters reach their highest position, which is 1.962 mm above the initial position, and in the remaining 20 ms of the free fall phase, they fall back to the initial position. In the next 20 ms, their speed is reversed so that the cycle can start again, passing through their lowest position, which is 0.981 mm below the initial position.

To further understand the neutron optical component according to the invention, embodiments of the invention are explained in more detail below with the aid of the schematic figures and diagrams. It shows:

FIG. 1 shows a side view of the neutron optical component,

FIG. 2 shows a front view of the structure according to FIG. 1, FIG. 3 shows a grille screen at the beginning of the structure,

FIG. 4 shows a grille panel at the end of the construction,

Figure 5 is a dimensioning table and

Figure 6 is a speed diagram for the function of the neutron optical component as a speed selector.

FIG. 1 shows a side view of the neutron-optical component 1 according to the invention for the neutron small-angle scatter measurement technology. The extension length 2 of the neutron-optical component 1 from the provision of a neutron beam, which takes place from the right in the exemplary embodiment shown, to the measurement sample is mainly defined by a high-precision carrier rail 3. It can have a length of, for example, 2 m to 20 m. A number n of support elements 4 are arranged in the guide groove of the support rail 3. In the selected exemplary embodiment, n = 20. The carrier elements 4 are vertical translation units 5 with a particularly high positioning accuracy, for example in one embodiment as micrometer screws. In the static application, these are set to a fixed value for a continuous neutron beam. In the dynamic case for a pulsed neutron beam, they (or piezo actuators used in their place) are continuously adjusted by drive units 6 or other drive units (not shown in FIG. 1) perform a movement of the entire carrier rail 3, which is then designed to be correspondingly flexible.

A perforated screen designed as a grid screen 7 is connected to each support element 4, so n = 20 grid screens 7 are present. For better illustration, a grating screen 7 is shown in the view at the beginning and end of the neutron-optical component 1. In the state of the neutron optical component 1 shown, all grating diaphragms 7 are aligned on a straight beam axis. In operation, the alignment takes place on one or more parabolic orbits for speed selection of the monochrome neutrons, as a result of which the neutron-optical component 1 according to the invention works not only as a focusing collimator but also as a speed selector. The distance between the grating diaphragms 7 is dependent on the extension length 2 and the optical guidance of the neutron beam. Since this still has a large divergence at the beginning of the neutron-optical component 1, a small spacing of the individual grating diaphragms 7 from one another is realized here, which ensures sufficient absorption of the neutrons not lying in the convergence region of the grating diaphragms 7 from the material of the grating diaphragms 7. With an increasing reduction in beam divergence and thus a decreasing absorption requirement due to the sequence of a plurality of grille shutters 7 in succession, the guide distance between the grille shutters 7 can be increased accordingly become. In the exemplary embodiment shown, a non-linear distance distribution between the grating diaphragms 7 is selected. With this an optimal reduction of the beam divergence can be achieved. Due to the close spacing of the carrier elements 4 in the initial region, it makes sense to drive the drive units 6 assigned to the carrier elements 4 in the dynamic case in order to achieve broadband, which can be connected to them at right angles, alternately on both sides of the carrier elements 4, which also alternate two parallel support rails 3, 8 can be arranged to align.

These details can be seen in FIG. 2, which shows the neutron-optical component 1 according to the invention from the front from the direction of the incident neutron beam, that is to say from the right in FIG. 1. The parallel carrier rails 3, 8 are shown in the lower area. On the support rail 3, the first support element 4 is arranged oriented to the left, which supports the first grille screen 7 in the upper region via a support frame 9. The support element 4 arranged on the rail 8 oriented to the right carries the second grille panel, which lies exactly behind the first grille panel 7 and therefore cannot be seen in FIG. 2. Both carrier elements 4 shown have carrier slides 10 in the lower region, by means of which they can be positioned along the carrier rails 3, 8 and fixed by means of knurled screws 11. In the central area, the carrier elements 4 are connected to the electrically controllable drive units 6 for the vertical adjustment of the grille shutters 7. The carrier frame 9 has a knurled screw 12 in the lower region for fine adjustment of the grille screen 7. In the exemplary embodiment shown, this is designed as a lattice frame 13 with square diaphragm openings 14.

In FIG. 3, the grating frame 13 according to FIG. 2 is shown in more detail on the input side (right side) of the neutron optical component 1. It is made of neutron absorbing cadmium with the help of high-precision manufacturing techniques (tolerance +/- 0.02 mm) and has 12 rows and 12 columns and thus m = 144 apertures 14. The neutron beam passing through the lattice frame 13 is divided according to the number m of the apertures 14 into m = 144 partial beams, each of which represents its own channel. Each partial beam is increasingly converged in the course of all grating frames 13 or grating diaphragms 7 and focused on the detector location. In the case of a relatively large transmission area on the measurement sample, a high resolution is nevertheless possible due to the high neutron intensity maintained and particularly high-quality small-angle scatter measurement on the measurement sample due to the focus on the detector location. The diaphragm openings 14 in the lattice frame 13 according to FIG. 3 are the largest in this example (2 mm × 2 mm). The horizontal and vertical web width here is 0.6 mm. The smallest diaphragm openings 14 (1 mm × 1 mm) are located in the lattice frame 13 on the output side (left side) of the neutron optical component 1 according to FIG. 4. Here, the web width is still 0.3 mm. The decrease in size of the individual aperture openings 14 and web widths can be clearly seen. This reduction, which corresponds to a narrowing of the individual channels and thus an improvement in their convergence, depends on the position of the grating frames 13 (or grating apertures 7) in the convergence cone of the neutron-optical component 1 according to the invention in order to achieve a large convergence of the apertures 14 partial beams formed. The absolute number of diaphragm openings 14 depends on the desired radiation area on the measurement sample, which should be as large as possible, and on the divergence reduction that can be achieved.

Dimensions of the aperture openings and webs for an exemplary embodiment can be found in the table in accordance with FIG. 5. The grid panel number i is listed in the first column. The absolute position pos of the grating diaphragms from the beginning (right) of the neutron optical component according to the invention is given in mm in the second column. The Divergence div can be found in the third column as a relative factor. Their reduction can be clearly seen with the progressive position of the grille shutters. The opening diameter of the square aperture is shown in mm in the fourth column. This decreases continuously from 2 mm to 1 mm. In the fifth column, the reduction factor redf associated with the reduction is listed. Such dimensions can easily be carried out with the aid of computer-aided calculation programs for any parameter constellations.

As already mentioned above, the neutron optical component according to the invention not only works as a focusing collimator, but also as a speed selector. The gravitation that affects the course of the parabolic orbits of the neutrons is used. The implementation of the speed selection for a neutron optical component with a transmission of square diaphragm openings of 3 mm to 1.5 mm over an extension length of 15 m chosen as an example is shown in the speed diagram according to FIG. 6 with a plot of the transmission trans over the wavelength wav. The left and right half curves each belong to different wavelength bands, i.e. different positions of the grating diaphragms on two different parabolic orbits. A special wavelength band can thus be selected by setting the parabolic orbit (applies to the static case of the continuous neutron beam; in the dynamic case of the pulsed neutron beam, all the wavelengths occurring in the neutron beam are continuously and cyclically traversed in accelerated motion). The design parameters of the neutron-optical component can therefore be easily set differently. LIST OF REFERENCE NUMBERS

1 neutron optical component

2 extension length

3 support rails

4 support element

5 translation unit

6 drive unit

7 grille screen

8 carrier rail

9 support frames

10 carrier slides

11 knurled screw

12 knurled screw

13 lattice frames

14 aperture

n Number of grating apertures m Number of aperture openings i Grating aperture number pos Position (m) div Divergence open Opening diameter redf Reduction factor trans Transmission wav wavelength

Claims

claims

1. Neutron-optical component for neutron small-angle scattering measurement technology with several, in the extension of the neutron beam from the neutron source to the measurement sample, the small-angle beam scattering of which is detected by a detector, pinholes made of a neutron-absorbing material, each with at least one active aperture, held in carrier elements to reduce the beam divergence, characterized in that, depending on the required measurement resolution and the extension length (2) of the neutron beam, a number n of perforated apertures, which are designed as grating apertures (7), which ensure beam guidance, is provided with a variable distance from one another, and that each Lattice aperture (7) has a constant number m of closely adjacent aperture openings (14) which divide the neutron beam passing through into a number m of partial rays and a size decreasing in the direction of the measurement sample to reduce the diverg Enz of the partial beams, wherein each of the diaphragm openings defining a partial beam (14) of all n grating diaphragms (7) are arranged at least in a time interval given by the flight time of monochrome neutrons on their parabolic path and all partial beams are focused on the detector.

2. Neutron optical component according to claim 1, characterized in that the diaphragm openings (14) have dimensions in a range from 1 mm to 2 mm.

3. Neutron optical component according to claim 1 or 2, characterized in that the diaphragm openings (14) are manufactured with the aid of computer-controlled manufacturing techniques with high manufacturing precision.

4. Neutron-optical component according to one of claims 1 to 3, characterized in that the distance between the grating diaphragms (7) increases in the direction of the measurement sample.

5. Neutron optical component according to one of claims 1 to 4, characterized in that the grating diaphragms (7) are designed as a grating frame (13) with square diaphragm openings (14).

6. Neutron optical component according to claim 5, characterized in that the lattice frame (13) are formed from cadmium.

7. Neutron-optical component according to one of claims 1 to 6, characterized in that the carrier elements (4) of the grating diaphragms (7) are designed as vertical translation units (5) with high positioning accuracy.

8. Neutron optical component according to claim 7, characterized in that the vertical translation units (5) are designed as actuators with micrometer screws or as piezo actuators.

9. Neutron optical component according to one of claims 1 to 8, characterized in that the aperture in a time interval given by the flight time of monochrome neutrons on the parabolic orbit of monochrome neutrons aperture openings (14) in other time intervals given by the flight time of other monochrome neutrons by corresponding local Shift the grille shutters (7) on their parabolic paths.

10. A neutron optical component according to claim 9, characterized in that the grating diaphragms (7) are moved continuously over the parabolic orbits of all monochrome neutrons occurring in the neutron beam.

11. The neutron-optical component according to claim 10, characterized in that the grating diaphragms (7) are moved in an oscillating manner between the uppermost and the lowest occurring parabolic path.

12. Neutron-optical component according to one of claims 9 to 11, characterized in that the displacement of the grating diaphragms (7) takes place via a corresponding timing of drive units (6) of the vertical translation units (5) or of support rails (3, 8) holding them ,

13. Neutron optical component according to claim 10, characterized in that the drive units (6) are designed as controlled servomotors, moving adjusting screws, stepping motor-driven adjusting screws or as piezoelectric actuators.

14. Neutron optical component according to one of claims 12 and 13, characterized in that the displacement of the grating diaphragms (7) takes place in time-defined acceleration phases.

15. Neutron optical component according to one of claims 1 to 13, characterized in that a resilient mounting is provided for the carrier elements (4) of the grating diaphragms (7).