Patent Description:
More particularly, the invention relates to an X-ray collimator and an X-ray inspection (and/or analysis) apparatus for non-invasive analysis of samples of material to be analysed.

It is known that certain qualities or physical properties of products and manufactured goods, such as density and/or chemical composition, can be determined by X-ray analysis using a beam of X-rays in transmission, reflection or in both measurement geometries. The photon beam produced by the X-ray sources, such as an X-ray tube, produces new X-ray beams because it is partly transmitted and partly reflected when the initially produced X-ray beam hits a sample of material to be analysed. By analysing that beam of X-rays transmitted or reflected by the sample of material, it is possible to obtain information about the physical nature of the object itself. For example, it is well known that the acquisition of the X-ray beam transmitted through a sample of a given material gives the opportunity to measure the surface mass density ρs of the sample of material analysed, according to Lambert Beer law, i.e. according to the following relation: <MAT> where, I<NUM> is the intensity of the X-ray beam emitted by the X-ray source (i.e. incident on the sample of material), I is the intensity of the X-ray beam transmitted by (i.e. exiting) the sample of material and Ψ is a material-specific constant of the material of which the sample of material is made.

An X-ray inspection apparatus generally comprises an X-ray source (or X-ray tube, i.e. an electron accelerator), which is configured to generate an X-ray beam, usually in the shape of a conical fan.

For this reason, the X-ray inspection apparatus normally comprises a collimator placed between the X-ray source and the sample of material to be analysed. The collimator is employed to shield the redundant beam of the X-ray beam, i.e. to select only the central portion of the X-ray beam that is less divergent than the beam itself in order to direct it towards the sample of material to be analysed.

The X-ray inspection apparatus further comprises a measurement detector, which is placed in a position such to receive the transmitted and/or reflected X-ray beam from the sample of material, so as to measure the intensity I of this transmitted and/or reflected X-ray beam.

By measuring the intensity I of the transmitted and/or reflected X-ray beam, the intensity I<NUM> of the X-ray beam emitted by the X-ray source being known, the X-ray inspection apparatus is able to determine the desired physical quantity of the sample of material, such as the mass surface density of the sample of material.

It is perceived in the field the need to make the determination of the physical quantity to be measured increasingly reliable and precise.

In fact, it has been observed that even a temporary variation/fluctuation (e.g. due to a voltage drop during the measurement or physiological irregularities in the emission of the X-ray beam by the X-ray source) in the intensity I<NUM> of the X-ray beam emitted by the X-ray source may cause an error or inaccuracy in determining the correct value of the physical quantity or, in any case, a low accuracy in the measurement. An example of a known X-ray collimator according to the preamble of claim <NUM> is disclosed in document D1: <CIT>.

An object of the present invention is to meet the aforesaid and other requirements of the prior art, with a simple, rational and low-cost solution.

Such objects are achieved by the characteristics of the invention reported in the independent claims. The dependent claims outline preferred and/or particularly advantageous aspects of the invention.

The invention, makes available an X-ray collimator in accordance with independent claim <NUM>.

It has been observed that, thanks to the configuration of the collimator, it is possible to position the reference detector close to the source, so that it can intercept part of the beam coming from the source, without affecting the beam arriving at the object.

Substantially, thanks to this solution, it is possible to obtain reliable and accurate measurements in any condition of use.

In practice, it is possible to make direct measurements of incident intensity in certain systems (e.g. density measurement of a fluid in a pipe).

In addition, it is possible to make precise and accurate measurements even if the emission of the beam from the X-ray source fluctuates over time, as such fluctuations have a direct influence on the accuracy of measurements in known systems.

Measuring continuously the beam emitted by the X-ray source, by means of the reference detector thus positioned in the collimator, allows the accuracy of the measurement made by the inspection apparatus to be optimised.

According to the invention, the collimator comprises a housing seat configured to house at least one portion of the reference detector, wherein the outlet of the derivation conduit leads into said housing seat at the inlet window of the reference detector.

According to an aspect of the invention, the distance between the outlet and the inlet of the derivation conduit can be advantageously less than the distance between the outlet and the inlet of the collimation conduit.

According to one embodiment, the derivation conduit may branch (directly) from the collimation conduit diverging therefrom and the inlet of the derivation conduit, in that case, communicates with the collimation conduit.

For example, this embodiment allows the peripheral portion of the beam to be channelled along the derivation conduit when the focus of the X-ray beam is placed within the collimation conduit.

According to an (alternative) further embodiment, the derivation conduit can be separated from the collimation conduit and the inlet of the derivation conduit is placed alongside the inlet of the collimation conduit and at a non-null distance from it.

For example, this embodiment allows the peripheral portion of the beam to be channelled along the derivation conduit when the focus of the X-ray beam is located outside (and upstream of) the collimation conduit.

In addition, the collimator body may comprise an attachment flange configured to be connected to the X-ray source.

For example, the inlet of the collimation conduit and/or the derivation conduit is located (flush with and) near the attachment flange.

For the same above mentioned purposes, the invention makes available an X-ray inspection apparatus on a sample of material to be analysed that comprises:.

According to an aspect of the invention, the measurement detector may face the outlet of the collimation conduit and at a non-null distance therefrom so as to receive X-rays transmitted through the sample of material, between the outlet of the collimation conduit and the measurement detector a gap being defined in which the sample of material is adapted to be housed.

Alternatively or additionally, the measurement detector can be placed alongside the outlet of the collimation conduit and at a non-null distance from it, in a position such to receive X-rays reflected by the sample of material.

According to a further aspect of the invention, the apparatus may comprise a support frame to which the X-ray source, the X-ray collimator and (e.g. also) the measurement detector are rigidly fixed.

Preferably, then, the apparatus may comprise an electronic control unit operatively connected to the measurement detector and the reference detector, wherein the electronic control unit may be configured to:.

Preferably, the indicative parameter may be a mass surface density.

Further features and advantages of the invention will be more apparent after reading the following description provided by way of a non-limiting example, with the aid of the accompanying drawings.

With particular reference to these figures, <NUM> globally refers to an X-ray inspection apparatus for determining and measuring a physical quantity of a sample of material, e.g. an object or a (finished) product or a portion thereof, globally referred to by the letter S.

The apparatus <NUM> comprises an X-ray source <NUM> configured to generate and emit an X-ray beam, generically referred to by the letter B.

The beam B has a substantially conical fan shape and is directed along a rectilinear central axis.

The conicity of the beam B emitted by source <NUM> is substantially comprised between <NUM>° and <NUM>°.

The source <NUM>, for example, comprises or consists of an X-ray tube.

The source <NUM> is provided with an emission window <NUM>, for example circular, from which the beam B exits (perpendicular to it).

The apparatus <NUM> also includes a collimator <NUM>, which is configured to collimate the beam B emitted by the source <NUM>.

The collimator <NUM> comprises a collimator body <NUM>, for example substantially cylindrical or prismatic, having a longitudinal axis A, which in use is arranged parallel (and coaxial) to the central axis of the beam B emitted by the source <NUM>.

The collimator body <NUM> comprises a first axial end, intended to be arranged proximal to the source <NUM>, and an opposite second axial end.

The collimator body <NUM> is, preferably, made in a single body or is made of a plurality of bodies assembled and rigidly fixed together.

In the collimator body <NUM>, a collimation conduit <NUM> is made that is provided with an inlet <NUM>, configured to be connected to the (emission window <NUM> of the) source <NUM> for the inlet of the beam B generated by it.

For example, the inlet <NUM> is arranged substantially in contact with (or proximal to) the emission window <NUM> of the source <NUM> and, preferably, has a shape and size equal to the shape and size of the emission window <NUM> itself.

The inlet <NUM> is defined at an axial end of the collimation conduit <NUM>.

Furthermore, the inlet <NUM> is, for example, defined at or near the first axial end of the collimator body <NUM>.

Preferably, the collimator body <NUM>, at the first axial end thereof, comprises an attachment flange <NUM>, e.g. circular and/or provided with axial through-holes, configured to be connected to the source <NUM>, e.g. by means of a threaded connection, engaging said through-holes.

The attachment flange <NUM> perimetrically surrounds the inlet <NUM> of the collimation conduit <NUM>.

The collimation conduit <NUM> further comprises an outlet <NUM> (axially opposite to the inlet <NUM>), which is configured to emit a collimated portion (i.e., a central portion B1 of the beam B, preferably having a conicity lower than or equal to the conicity of the beam B emitted by the source <NUM>).

The outlet <NUM> is defined at an axial end of the collimation conduit <NUM> opposite to the axial end thereof concerned by the inlet <NUM>.

The outlet <NUM> is, for example, defined at or near the second axial end of the collimator body <NUM>.

The inlet <NUM> and/or outlet <NUM> may be opened (through) or occluded by a window of X-ray transparent material.

Preferably, the collimation conduit <NUM> has a rectilinear longitudinal axis, preferably coinciding with the longitudinal axis A of the collimator body <NUM> (i.e. in use it is arranged parallel and coaxial to the central axis of the beam B emitted by the source <NUM>).

For example, the collimation conduit <NUM> has a substantially cylindrical shape (having a constant cross-section throughout its longitudinal extension, with the inlet <NUM> and the outlet <NUM> defining the opposite open axial ends of the collimation conduit <NUM> itself).

The collimation conduit <NUM> has a (minimum) internal diameter substantially equal to (or less than) the diameter of the emission window <NUM> of the source <NUM>.

The collimation conduit <NUM>, furthermore, has a length (given by the axial distance between the inlet <NUM> and the outlet <NUM>) substantially equal to (or greater than) <NUM> times the diameter, for example equal to <NUM>.

It is not excluded that the collimation conduit <NUM> may have a conical shape (e.g. converging from the inlet <NUM> towards the outlet <NUM>).

The collimator body <NUM> and/or at least one internal lining of the collimation conduit <NUM> is made of at least one material adapted to shield/absorb X-rays (of the beam B emitted by the source <NUM>).

For example, such a material is selected from the group consisting of tungsten, lead, steel, bronze and brass; preferably it is tungsten.

In practice, the collimation conduit <NUM> is configured to cut the emission cone of the beam B, so as to let only an internal portion B1 thereof pass towards the outlet <NUM> and to shield/absorb an external, more divergent portion thereof.

In addition, a derivation conduit <NUM> is provided in the collimator body <NUM>.

The derivation conduit <NUM> comprises an inlet <NUM>, configured to let at least a peripheral portion B2 of the beam B emitted by the source <NUM> enter the derivation conduit <NUM>.

For example, the inlet <NUM> of the derivation conduit <NUM> is defined at an axial end of the derivation conduit <NUM>.

In a first embodiment shown in <FIG> and <FIG>, for example, the inlet <NUM> of the derivation conduit <NUM> opens (and branches out) at the collimation conduit <NUM>.

In particular, the inlet <NUM> of the derivation conduit <NUM> opens at an axial section of the collimation conduit <NUM> proximal to the inlet <NUM> of the collimation conduit <NUM> itself.

The inlet <NUM> defines a radial or substantially radial opening of the collimation conduit <NUM>. Preferably, one end of the inlet <NUM> substantially coincides with the inlet <NUM> of the collimation conduit <NUM>.

Further, the inlet <NUM> of the derivation conduit <NUM>, i.e., its proximal end at the inlet <NUM> of the collimation conduit <NUM>, is defined at or near the first axial end of the collimator body <NUM>.

In a second embodiment shown in <FIG>, the derivation conduit <NUM> is separated from the collimation conduit <NUM>.

In this second embodiment, the inlet <NUM> of the derivation conduit <NUM> is placed alongside (radially) the inlet <NUM> of the collimation conduit <NUM> and at a non-null distance therefrom. Furthermore, the inlet <NUM> of the derivation conduit <NUM> is, for example, defined at or near the first axial end of the collimator body <NUM> (at the side of the inlet <NUM> of the collimation conduit <NUM>, for example, coplanar thereto).

The inlet <NUM> defines, in such a case, an axial or substantially axial opening of the collimator body <NUM> (arranged at the first axial end thereof).

In both embodiments, then, the derivation conduit <NUM> further comprises an outlet <NUM> (axially opposite to the inlet <NUM>), which is configured to emit the peripheral portion B2 of beam B that has entered the inlet <NUM> (and travelled through the derivation conduit <NUM>). The outlet <NUM> is defined at an axial end of the derivation conduit <NUM> opposite the axial end of the derivation conduit concerned by the inlet <NUM>.

The outlet <NUM> is, for example, defined as proximal to the second axial end of the collimator body <NUM>, preferably at a non-null distance therefrom.

Preferably, the derivation conduit <NUM> has a rectilinear longitudinal axis C.

The longitudinal axis C of the derivation conduit <NUM> is inclined by a predetermined angle α with respect to the longitudinal axis A of the collimation conduit <NUM> (so as to diverge from it), wherein the angle α is, preferably, an acute angle, for example an angle less than or equal to the maximum divergence angle of the (conical fan defined by the) beam B emitted by the source <NUM>.

The derivation conduit <NUM>, in particular, is configured to be passed through (from inlet <NUM> to outlet <NUM>) by an angular portion of the perimeter portion B2 (circular) of the beam B emitted by the source <NUM>.

For example, the derivation conduit <NUM> has a substantially cylindrical shape (with a constant cross-section throughout its longitudinal extension, with the inlet <NUM> and the outlet <NUM> defining the opposite open axial ends of the derivation conduit <NUM> itself).

The derivation conduit <NUM> has an internal (minimum) diameter substantially equal to (or less than) the internal diameter of the collimation conduit <NUM>.

Advantageously, the derivation conduit <NUM> has a length (given by the axial distance between the inlet <NUM> and the outlet <NUM>) substantially less than (or at most equal to) the length of the collimation conduit <NUM>.

In other words, the distance between the outlet <NUM> and the inlet <NUM> of the derivation conduit <NUM> is less than the distance between the outlet <NUM> and the inlet <NUM> of the collimation conduit <NUM>.

An internal lining of the derivation conduit <NUM> is made of at least one material adapted to shield/absorb X-rays (of the beam B emitted by the source <NUM>).

A housing seat <NUM> (e.g. cylindrical) is also provided in the collimator body <NUM>, which is arranged for example proximal to the second axial end of the collimator body <NUM> itself.

The housing seat <NUM> is, for example, defined by a cavity (open on one side, for example open at the second axial end of the collimator body <NUM>) made in the collimator body <NUM>, for example laterally with respect to (the outlet <NUM> of) the collimation conduit <NUM>.

According to the invention, the housing seat <NUM> comprises a back wall <NUM>, substantially orthogonal to the longitudinal axis C of the derivation conduit <NUM>.

The outlet <NUM> of the derivation conduit <NUM> leads to (and is contained in) the (back wall <NUM>) of the housing seat <NUM>.

The apparatus <NUM>, and preferably the collimator <NUM>, further comprises a reference detector <NUM>, which is configured to receive at least a portion of the beam B, for example at least a perimeter portion B2 of the beam B that has passed through the derivation conduit <NUM>. The reference detector <NUM> is for example a spectroscopic sensor based on CdZnTe (CZT). Preferably, the reference detector <NUM> is configured to measure a value v<NUM> of intensity I (of the perimeter portion B2) of the beam B it is intended to receive.

The reference detector <NUM> comprises an inlet window <NUM> configured to receive (the perimeter portion B2 de) the beam B.

For example, the reference detector <NUM> is rigidly fixed to the collimator body <NUM>. Advantageously, the reference detector <NUM> is accommodated (at least partially) within the housing seat <NUM> (e.g. substantially to measure).

In the example, the reference detector <NUM> protrudes outside the collimator body <NUM> (e.g. from the side of its second axial end), i.e. from the open end of the housing seat <NUM>.

It is not excluded, however, that the reference detector <NUM> may be contained entirely within (the housing <NUM> of) the collimator body <NUM>.

For example, the inlet window <NUM> faces (and is adjacent to) the outlet <NUM> of the collimation conduit <NUM>.

In practice, the entire perimeter portion B2 of the beam B passing through the collimation conduit <NUM> is conveyed into the reference detector <NUM> (through the inlet window <NUM> thereof).

The apparatus <NUM> further comprises a measurement detector <NUM> (e.g. separate from the collimator <NUM>, although it may be rigidly fixed thereto).

The measurement detector <NUM> is configured to receive at least a transmitted and/or reflected portion B3 of the beam B that was transmitted through the sample of material S (not absorbed by it) and/or reflected by the sample of material S, or a part (transmitted and/or reflected) of the central portion B1 of the beam that (exiting from the outlet <NUM> of the collimation conduit <NUM> of the collimator <NUM>) interacted with the sample of material S (passing through it to be transmitted and/or being reflected by it).

The measurement detector <NUM> is for example a spectroscopic sensor based on CdZnTe (CZT).

Preferably, the measurement detector <NUM> is configured to measure a value v<NUM> of intensity I of the transmitted and/or reflected portion B3 of the beam B that it is intended to receive. The measurement detector <NUM> includes an inlet window <NUM> configured to receive a transmitted and/or reflected portion B3 of the beam B.

For example, the measurement detector <NUM> faces the outlet <NUM> of the collimation conduit <NUM> of the collimator <NUM> and at a non-null distance, i.e., the inlet window <NUM> of the measurement detector <NUM> faces (and is parallel to) the outlet <NUM> of the collimation port <NUM>, i.e., is arranged orthogonal to the central axis of the beam B.

In such a case, the measurement detector <NUM> is configured to receive at least a transmitted portion B3 of the beam B that was transmitted through the sample of material S (not absorbed by it).

Substantially, the measurement detector <NUM> is placed on the opposite side of the collimator <NUM> with respect to the sample of material S to be analysed.

The distance between (the inlet window <NUM> of) the measurement detector <NUM> and (the outlet <NUM> of) the collimation conduit <NUM> is greater than or equal to the maximum thickness of the sample of material S to be inspected by the apparatus <NUM>.

For example, this distance can be adjusted according to (the thickness of) the sample of material S to be analysed.

In practice, between (the inlet window <NUM> of) the measurement detector <NUM> and (the outlet <NUM> of) the collimation conduit <NUM>, a cavity is defined in which the sample of material S is adapted to be received, for example supported by a support, as it will be better described below.

Alternatively or additionally, for example, the measurement detector <NUM> is flanked (radially) with the outlet <NUM> of the collimation conduit <NUM> of the collimator <NUM> (version not illustrated in the drawings) and preferably at a non-null distance therefrom, i.e. the inlet window <NUM> of the measurement detector <NUM> is flanked with the outlet <NUM> of the collimation conduit <NUM>, e.g. inclined with respect to it, i.e. arranged orthogonal to a central axis thereof inclined with respect to the central axis of the beam B by an angle β, wherein the angle β is the angle of reflection of the central portion B of the beam B on the sample of material S.

For example, the angle β may be adjusted according to the sample of material S to be analysed.

In such a case, the measurement detector <NUM> is configured to receive at least a reflected portion B3 of the beam B that has been reflected by the sample of material S (not absorbed by it).

Substantially, the measurement detector <NUM> is arranged on the same side of the collimator <NUM> with respect to the sample of material S to be analysed.

According to a preferred embodiment, the apparatus <NUM> comprises a support frame <NUM>, for example a rigid one (i.e., one that is non-deformable to the usual stresses to which it is intended to be subjected in operation), which preferably also defines or comprises a substantially closed casing.

The source <NUM>, the collimator <NUM> (with the reference detector <NUM>) and preferably also the measurement detector <NUM> are fixed rigidly to the support frame <NUM>, e.g. contained therein. Preferably, the support frame <NUM> (in case the measurement detector <NUM> is configured to receive at least a transmitted portion B3 of the beam B) defines said gap.

In this case, the support frame <NUM> has a substantially (overall) "C" shape, in which on one branch the source <NUM>, the collimator <NUM> (with the reference detector <NUM>) are fixed (and contained) and on the other branch the measurement detector <NUM> is fixed (and contained).

According to an aspect of the invention, the apparatus <NUM> further comprises an electronic control unit <NUM> operatively connected to the measurement detector <NUM> and the reference detector <NUM>.

The electronic control unit <NUM> comprises, for example, a processing module, such as a microprocessor or a processor, and a storage module.

The electronic control unit <NUM> is, for example, connected to a user interface, such as a screen and/or terminal or the like, through which a user can enter input values and/or receive information regarding output values transmitted and/or received by the electronic control unit <NUM>.

The electronic control unit <NUM> is preferably configured to perform the determination/measurement of a (qualitative and/or quantitative) parameter indicative of the type (i.e. of a physical quantity) of the sample of material S, for example of the mass surface density ρs of the sample of material S.

For example, the electronic control unit <NUM> is configured to compare the measured value v<NUM> of the intensity I (of the transmitted and/or reflected portion B3 of the beam B), measured in a predetermined time interval by the measurement detector <NUM>, with the reference value v<NUM> of intensity I (of the peripheral portion B2 of the beam B), measured in the same time interval by the reference detector <NUM>.

For example, the electronic control unit <NUM> is configured to repeat the aforesaid comparison for the entire measurement time, wherein the source <NUM> generates the beam B (which hits the sample of material S).

The electronic control unit <NUM>, is therefore configured to determine a value ρs of the aforesaid indicative parameter (i.e., the mass surface density ρs) of the sample of material S based on a comparison between the measured value v<NUM> of the intensity I (of the transmitted and/or reflected portion B3 of the beam B) and the reference value v<NUM> of intensity I (of the peripheral portion B2 of the beam B).

For example, the electronic control unit <NUM> is configured to calculate the value ρs (of the mass surface density) using the following formula:
<MAT>
wherein:.

The mass attenuation coefficients µi(ε) are known and tabulated for each element.

For example, the apparatus <NUM> described above may be used in a plant (e.g., a plant producing manufactured products and/or objects defining samples of material S to be analysed).

The system may comprise a conveyor, configured to define the aforesaid support for the samples of material S to be analysed, which has a support surface (e.g. horizontal), preferably movable, on which the samples of material S to be analysed rest (and advance).

The apparatus <NUM>, e.g. its support frame <NUM>, may be fixed (rigidly or movably) to the conveyor, e.g. to an edge thereof, such that the outlet <NUM> of the collimator <NUM> directs the central axis of the beam B towards the sample of material S resting on the support plane of the conveyor, e.g. substantially orthogonal to that support plane.

The apparatus <NUM> may be configured to perform the aforesaid inspection/measurement on each of the samples of material S passing through it (on the conveyor) or on a predetermined (random) number of samples of material S, as required.

Claim 1:
An X-ray collimator (<NUM>) that comprises:
- a collimator body (<NUM>) comprising:
∘ a collimation conduit (<NUM>) provided with an inlet (<NUM>), configured to be connected to an X-ray source (<NUM>) for the inlet of a beam (B) of X-rays, and an outlet (<NUM>), configured to emit a collimated portion (B1) of the X-ray beam (B); and
∘ a derivation conduit (<NUM>) inclined with respect to the collimation conduit (<NUM>), wherein the derivation conduit (<NUM>) is provided with an inlet (<NUM>), configured to be connected to the X-ray source (<NUM>) for the inlet of a peripheral portion (B2) of the same X-ray beam (B) emitted by the source (<NUM>), and an outlet (<NUM>);
- a reference detector (<NUM>) fixed to the collimator body (<NUM>) and characterized in that the reference detector is provided with an inlet window (<NUM>) facing the outlet (<NUM>) of the derivation conduit (<NUM>) and the collimator body (<NUM>) comprises a housing seat (<NUM>) configured to house at least one portion of the reference detector (<NUM>) and comprises a back wall (<NUM>), substantially orthogonal to the longitudinal axis (C) of the derivation conduit (<NUM>), wherein the outlet (<NUM>) of the derivation conduit (<NUM>) leads into said housing seat (<NUM>) at the inlet window (<NUM>) of the reference detector (<NUM>).