Patent Description:
Analyzer devices that make use of X-ray spectrometry are typically employed, for example, for analysis of the elemental composition of a bulk sample or for determination of a thickness and elemental composition of a coating on a bulk substrate. X-ray spectrometry is based on the physical principle of X-ray fluorescence (XRF). A non-limiting example in this regard is energy dispersive X-ray spectrometry (EDX), which is employed in the following as a non-limiting example of techniques that rely on XRF.

<FIG> schematically illustrates some components of an EDX device. When powered, an X-ray tube <NUM> emits primary X-radiation that is used to excite X-ray fluorescence in a sample <NUM> under study. The primary X-rays emitted from the X-ray tube <NUM> are considered as a primary X-ray beam <NUM> and it may be provided in the soft and/or ultra-soft X-radiation regime. During an analysis, a shutter <NUM> is opened in order to let a primary X-radiation pass towards the sample <NUM>. Alternatively, the X-ray tube <NUM> is only powered during analysis of the sample <NUM> and depowered otherwise. In some setups, a primary filter <NUM> is brought into the primary beam <NUM>. The physical realization of a primary filter may be, for example, a metallic plate with a thickness in the range of a few micrometers to several hundred micrometers. The primary filter <NUM> may be applied to modify the spectral distribution of the primary X-radiation in order to improve spectral sensitivity of the analysis. In a typical EDX device the primary filter <NUM> is implemented either as single fixed filter assembly or as an adjustable electro-mechanical filter assembly that allows for switching between primary filters of different characteristics.

In order to have a well-defined analysed area of the sample surface, the primary X-ray beam <NUM> is typically (but not exclusively) collimated by passing it through a collimator <NUM>, which is predominantly realized by an aperture of desired shape and size arranged in a metallic plate. Typical aperture shapes include, for example, circular or rectangular apertures. The implementation of the collimator <NUM> can be either a fixed single metallic aperture of predefined shape and size or an electro-mechanical assembly that allows for to switch between apertures of different size and/or shape. Finally, the collimated and filtered primary X-ray beam <NUM> irradiates the sample <NUM> and thereby interacts with the sample material. Irradiation of the sample <NUM> invokes secondary X-radiation <NUM> to be emitted from the sample <NUM>, including secondary X-ray fluorescence.

An energy dispersive detector <NUM> is used to collect the secondary X-radiation <NUM> emitted from the sample <NUM> in the direction of the detector window of the energy dispersive detector <NUM>. The detector <NUM> generates an electrical signal that is descriptive of the secondary X-radiation <NUM>, which electrical signal is provided to a multi-channel analyser <NUM> for analysis therein. An analysis across multiple channels enables deriving a spectrum of the secondary X-radiation <NUM> emitted from the sample <NUM> in a solid angle spanned by the detector window. An EDX device may further include a video microscopy arrangement integrated therein for observing and aligning the analysed portion of a surface of the sample <NUM>.

In various applications of XRF devices, such as intensity mapping of the sample surface, coating thickness analysis, samples with fine structures, etc.) it is often desirable to have a high lateral spatial resolution. With the typical setup described in the foregoing with references to <FIG>, a sufficiently high lateral spatial resolution can only be realized by implementing the collimator <NUM> such that it has an aperture that is sufficiently small in size. In this regard, typical aperture sizes (e.g. a diameter of a circular aperture or a diagonal of a rectangular aperture) are in the range of a few ten micrometers to a few hundred micrometers. Consequently, XRF devices that employ an electro-mechanical collimator assembly that enables switching between apertures of different shapes and/or sizes require accurate positioning of a selected aperture with respect to the primary X-ray beam <NUM> such that the collimated primary X-ray beam is accurately guided to a desired measurement location on the surface of the sample <NUM>. Typically, required positioning precision is in the order of a fraction of the size (e.g. diameter or diagonal) of the selected aperture.

In related art, <CIT> discloses an X-ray analyzer comprising a mechanism for selecting an iris passing a second order X-ray, comprising a collimator plate having a plurality of apertures of different size, and a stepper motor for rotationally positioning the collimator plate so as to keep a selected one of the plurality of apertures spatially aligned with a predefined axis along which a collimated X-ray beam is to be provided.

It is therefore an object of the present invention to provide a collimator assembly for an X-ray spectrometer device such that the collimator assembly enables positioning of collimator apertures available in the X-ray spectrometer device at improved spatial precision.

In the following a simplified summary of some embodiments of the present invention is provided in order to facilitate a basic understanding of the invention. The summary is not, however, an extensive overview of the invention.

In accordance with the invention, a collimator assembly for an X-ray spectrometer device is provided, the collimator assembly comprising a rotatable gear assembly comprising a worm gear assembly and including a collimator plate having a plurality of apertures of different size and/or shape arranged therein; a driving assembly comprising a worm screw for rotating the gear assembly and an electric motor for rotating the worm screw to bring the gear assembly into a rotational position where a selected one of the plurality of apertures is spatially aligned with a predefined axis along which a collimated X-ray beam is to be provided from the X-ray spectrometer device; and a magnet arrangement for generating a magnetic force that is arranged to push or pull the gear assembly into a predefined direction of rotation to prevent rotational movement due to backlash, thereby keeping the selected one of the plurality of apertures spatially aligned with said predefined axis.

In accordance with another aspect of the invention, an energy dispersive X-ray spectrometer device is provided, the device comprising said collimator assembly.

The novel features which are considered as characteristic of the invention are set forth in the appended claims. The invention itself, however, both as to its construction and its method of operation, together with additional objects and advantages thereof, will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.

<FIG> schematically illustrates some aspects of an exemplifying collimator assembly <NUM> for an X-ray spectrometer device. As described in the foregoing, energy dispersive X-ray spectrometry (EDX) serves as a non-limiting example of techniques that rely on X-ray spectrometry, and in the following, where applicable, EDX is predominantly employed as a non-limiting example in this regard.

The EDX device making use of the collimator assembly <NUM> may be operable, for example, along the outline described in the foregoing with references to <FIG>, while the collimator assembly <NUM> may be used to serve as the collimator <NUM> described in context of <FIG>. The collimator assembly <NUM> is provided as a worm drive where a worm <NUM> that is rotatable by an electric motor <NUM> is arranged to drive a (circular) worm gear assembly <NUM> having teeth <NUM> arranged on its outer perimeter. The electric motor <NUM> may be provided, for example, as a stepper motor. The worm <NUM> and the electric motor <NUM> may be jointly referred to as a driving assembly that serves to drive the worm gear assembly <NUM>. <FIG> further shows a vertical line A that indicates the axis of rotation of the worm gear assembly <NUM> The worm <NUM> may be alternatively referred to as a worm screw <NUM>, whereas the worm gear assembly <NUM> may be alternatively referred to as a worm wheel assembly <NUM>.

The collimator assembly <NUM> further comprises a magnet <NUM> arranged in a fixed position with respect to the worm gear assembly <NUM>. The magnet <NUM> is referred to in the following a stationary magnet <NUM> due to its fixed position with respect to the worm gear assembly <NUM>. The worm gear assembly <NUM> further comprises a collimator plate <NUM> having a plurality of apertures arranged therein and a frame ring <NUM> arranged to hold a plurality of magnets <NUM> in respective fixed positions with respect to the collimator plate <NUM>. The magnets <NUM> are referred to in the following as latch magnets <NUM> since they serve to facilitate keeping the worm gear assembly <NUM> - and hence the apertures in the collimator plate <NUM> - in a desired rotational position, as will be described in more detail in the following.

<FIG> schematically illustrates the collimator assembly <NUM> from a different angle and, in particular, shows a partial cross-section of some elements thereof to facilitate more detailed description of its components and operation. <FIG> shows a vertical line B that indicates the axis along which a collimated X-ray beam is provided from the EDX device making use of the collimator assembly <NUM>. In the following, the line B is also referred to as an axis B, as a reference axis or as a nominal axis. The collimator plate <NUM> has a plurality of apertures <NUM> arranged therein, each aperture <NUM> serving as a collimator when the worm gear assembly <NUM> is rotated into a position where the center of a respective aperture <NUM> spatially coincides with the primary X-ray beam at position of the axis B (i.e. the reference axis). Typically, the width (i.e. the radius or diameter) of the primary X-ray beam is substantially larger than that of the apertures <NUM>, an aperture <NUM> thereby allowing a narrow sub-portion of the primary X-ray beam to pass the collimator plate <NUM> as the collimated primary X-ray beam towards a desired location in the sample surface. The apertures <NUM> are different in size and/or shape, thereby providing different collimation characteristics. Note that for graphical clarity only some of the apertures <NUM> are explicitly pointed out in the illustration of <FIG>, while the example therein includes eight apertures <NUM> in total.

Each of the plurality of latch magnets <NUM> secured in its respective position by the frame ring <NUM> is arranged in a respective position with respect to a corresponding one of the apertures <NUM> in the collimator plate <NUM>. Hence, the plurality of latch magnets <NUM> and the plurality of apertures <NUM> constitute a plurality of magnet-aperture pairs that serve to firmly hold a given one of the apertures <NUM> in a desired rotational position after having been brought therein by operation of the worm drive provided by the worm screw <NUM>, the electric motor <NUM> and the worm gear assembly <NUM>. In this regard, the desired rotational position is the one where the given one of the apertures <NUM> spatially coincides with the axis B as accurately as possible, as described in more detail in the following.

In practice, the worm drive typically involves some positional inaccuracy due to backlash caused by slightly loose mesh between the teeth <NUM> of the worm gear assembly <NUM> and those of the worm screw <NUM>: once the worm gear assembly <NUM> has been driven by the worm drive to a desired rotational position, due to inevitable 'looseness' in the match between the teeth <NUM> of the worm gear assembly <NUM> and those of the worm screw <NUM> there is some 'wiggle room' for the rotational position of the worm gear assembly <NUM>, which may allow a small further rotational movement of the gear assembly <NUM>, which is commonly referred to as backlash. Even though the positional inaccuracy resulting from the backlash may be small in absolute value, in many scenarios it has a detrimental effect to the collimation characteristics of the system due to resulting uncontrolled mismatch between position of the center of the respective aperture <NUM> and the axis B. Hence, even though the given one of the apertures <NUM> may spatially coincide with the primary X-ray beam despite the positional mismatch, the resulting collimated X-ray beam may not meet the sample surface at or close enough to the desired location indicated by the axis B, which typically results in compromised analysis performance.

In theory, the positional accuracy could be improved by providing a tighter (or closer) mesh between the teeth <NUM> of the worm gear assembly <NUM> and those of the worm screw <NUM>. However, this would necessarily only partially address the problem of positional inaccuracy since in any real-life arrangement there is inevitably at least some level of backlash involved, while on the other hand a tighter (or closer) mesh would result in increased friction between the worm gear assembly <NUM> and the worm screw <NUM>, thereby preventing sufficiently smooth rotation of the worm gear assembly <NUM>.

In the collimator assembly <NUM>, the arrangement of the latch magnets <NUM> and the apertures <NUM> in the worm gear assembly <NUM> in combination with a suitable (fixed) position of the stationary magnet <NUM> with respect to the worm gear assembly <NUM> enables overcoming the positional inaccuracy resulting from the backlash in the worm drive system and, consequently, enables improved accuracy in positioning a selected one of the apertures <NUM> to spatially coincide with the axis B that indicates the desired axis of the collimated X-ray beam. Some aspects concerning an exemplifying arrangement of the latch magnets <NUM>, the apertures <NUM> and the stationary magnet <NUM> are described in the following with references to <FIG>, which provides a schematic plan view to a partial cross-section of the worm gear assembly <NUM> together with the stationary magnet <NUM>.

In the example of <FIG>, the worm gear assembly <NUM> is shown with the collimator plate <NUM> having the plurality apertures <NUM> arranged therein. As described in the foregoing, the apertures <NUM> are different in size and/or shape, thereby providing different collimation characteristics. The collimator plate <NUM> is surrounded by the plurality of latch magnets <NUM> arranged to surround the collimator plate <NUM> in respective fixed positions with respect to the collimator plate <NUM> and the apertures <NUM> therein. The latch magnets <NUM> may be secured in the respective positions by using the frame ring <NUM> having the plurality of latch magnets <NUM> arranged therein or by using other suitable structure for fixing the magnets into the worm gear assembly <NUM>. The stationary magnet <NUM> is positioned in the same or substantially the same plane with the worm gear assembly <NUM> outside the perimeter of the worm gear assembly <NUM>. In the example of <FIG> the stationary magnet <NUM> and the latch magnets <NUM> are arranged with respect to each other such that a repelling magnetic force between the stationary magnet <NUM> and one of the latch magnets <NUM> brought into proximity of the stationary magnet <NUM> is created. Such an arrangement of the magnets <NUM>, <NUM> may be provided e.g. by arranging them with respect to each other such that the same magnetic poles of the stationary magnet <NUM> and the latch magnet <NUM> that is brought into proximity thereof are facing each other. In the example of <FIG> this may be provided e.g. by arranging the stationary magnet <NUM> such that a predefined one of its magnetic poles (e.g. the north pole) is facing the worm gear assembly <NUM> and arranging each of the latch magnets <NUM> in the worm gear assembly <NUM> such that said predetermined one of the magnetic poles therein (e.g. the north pole) is facing the outer perimeter of the worm gear assembly <NUM>. The stationary magnet <NUM> and the plurality of the latch magnets <NUM> may be jointly referred to as a magnet arrangement, whereas the stationary magnet <NUM> and the plurality of the latch magnets <NUM> may be referred to as components of the magnet arrangement.

For graphical clarity of the illustration, <FIG> explicitly indicates only two of the apertures 109a, 109b with dedicated reference designators, while the illustration shows eight apertures <NUM> in total. Similarly, only two of the latch magnets 108a, 108b are explicitly indicated using dedicated reference designators, while the illustration shows eight latch magnets <NUM> in total. In the example of <FIG>, the latch magnet 108a is aligned in a radial direction with the aperture 109a, the latch magnet 108a and the aperture 109a thereby forming a magnet-aperture pair in this example. Similarly, another magnet-aperture pair of this example is formed by the latch magnet 108b and the aperture 109b that are likewise aligned in a radial direction - and the same holds also for the remaining radially aligned pairs of a latch magnet <NUM> and the aperture <NUM>.

The illustration in <FIG> further shows the position of the axis B that denotes the desired position of the axis of the collimated X-ray beam and the position of the axis A that denotes the axis of rotation, where both axes A and B are perpendicular or substantially perpendicular to the plane of the worm gear assembly <NUM> illustrated in <FIG>. Each of the plurality of latch magnets <NUM> is arranged at the same or substantially the same distance from the position of the axis A. Yet further, <FIG> also illustrates a line C that extends in a radial direction from the position of the axis A via the position of the axis B, while the stationary magnet <NUM> is offset from the (conceptual) line C in a first direction of rotation, which in the illustration of <FIG> is the clockwise direction, also indicated by a curved arrow D. It should be noted that the first direction of rotation that in the example of <FIG> (as well as in subsequent examples) is the clockwise direction is predominantly applied to assist discussion concerning positioning of the magnets. This is, however, a non-limiting choice made for clarity and brevity of description and hence in other examples the 'first direction of rotation' may be the counter-clockwise direction.

The worm drive may be employed to rotate the worm gear assembly <NUM> to bring the desired one of the apertures <NUM> (in the example of <FIG> the aperture 109a) into a position where its center is spatially aligned with the axis B. The rotation may be in the first direction of rotation or opposite to the first direction of rotation. Without the arrangement of magnets <NUM> and 108a the backlash would allow a small further rotational movement of the worm gear assembly <NUM> (e.g. in the clockwise direction), which in turn would result in misalignment between the center of the aperture 109a and the axis B. However, in the example illustrated in <FIG> the repelling magnetic force between the stationary magnet <NUM> and the latch magnet 108a serves as a retraction force that pushes the worm gear assembly <NUM> into a predefined direction of rotation that in the example of <FIG> (as well as in the subsequent examples) is the direction the opposite of the first direction of rotation (e.g. the counter-clockwise direction). This retraction force ensures keeping a side of a tooth of the worm gear assembly <NUM> pressed against the tooth of the worm screw <NUM> to prevent the further rotational movement that would be otherwise allowed by the backlash, thereby keeping the center of the aperture 109a spatially aligned with the axis B.

The magnet arrangement illustrated in the example of <FIG> may be varied in a number of ways without departing from the same inventive idea. As an example, the magnet-aperture pair is not necessarily formed by the aperture <NUM> and the latch magnet <NUM> that are aligned in a radial direction with each other. As an example in this regard, <FIG> schematically illustrates another exemplifying magnet arrangement, where the stationary magnet <NUM> is positioned with respect to the axis B in manner different from that applied in the example of <FIG>: the stationary magnet <NUM> is offset from the (conceptual) line C' that extends in a radial direction from the position of the axis A via a position that is offset from the position of the axis B in the angular direction. Also in this example the offset of the stationary magnet <NUM> from the (conceptual) line C' is to the first direction of rotation (e.g. the clockwise direction as indicated by the curved arrow D). Hence, in the example of <FIG> the repelling magnetic force that serves as the retracting force that ensures keeping the correct spatial alignment between the aperture 109a and the axis B is created by the stationary magnet <NUM> and the latch magnet 108b, while in this scenario the latch magnet 108b and the aperture 109a form a magnet-aperture pair.

<FIG> schematically illustrates a further example of the magnet arrangement, where the plurality of latch magnets <NUM> and the plurality of apertures <NUM> are not aligned with each other in a radial direction. In the example of <FIG>, the stationary magnet <NUM> is offset from the (conceptual) line C" that extends in a radial direction from the position of the axis A via a position that is (angularly) offset from the position of the axis B. Also in this example the offset of the stationary magnet <NUM> from the (conceptual) line C" is to the first direction of rotation (e.g. the clockwise direction indicated by the curved arrow D). In the example of <FIG>, the repelling magnetic force that serves as the retracting force that ensures keeping correct spatial alignment between the aperture 109a and the axis B is created by the stationary magnet <NUM> and the latch magnet 108a, the latch magnet 108a and the aperture 109a thereby forming a magnet-aperture pair in this scenario.

In general, in a scenario exemplified via <FIG> the repelling magnetic force, which serves to provide the retracting force for securing the worm gear assembly <NUM> into a desired rotational position is created by the stationary magnet <NUM> and the one of the latch magnets <NUM> that is closest to the stationary magnet <NUM> when the worm gear assembly <NUM> is brought into a rotational position where a selected one of the apertures <NUM> (e.g. the aperture 109a) is spatially aligned with the axis B. In a further exemplifying variation of the scenario depicted in <FIG>, there may be a plurality of stationary magnets arranged in respective fixed positions with respect to the worm gear assembly <NUM> and/or the axis B. As an example in this regard, a first stationary magnet may be arranged in the position described in the example of <FIG> whereas a second stationary magnet may be arranged in the position described in the example of <FIG>. In general, there may be a respective stationary magnet arranged in a position having an above-described angular offset to a respective one of the latch magnets <NUM> for one or more of the latch magnets <NUM> when the worm gear assembly <NUM> is brought into a rotational position where a selected one of the apertures <NUM> (e.g. the aperture 109a) is spatially aligned with the axis B.

<FIG> schematically illustrates yet another variation of the magnet arrangement. In this example, the stationary magnet <NUM> is illustrated using a hatched outline to illustrate its position in a plane that is parallel with the plane of the worm gear assembly <NUM>. In other words, in the example of <FIG> the stationary magnet <NUM> is positioned in a plane that is either 'below' or 'above' the worm gear assembly <NUM>. Moreover, the stationary magnet <NUM> is arranged in its plane in a distance from the axis A that is the same or substantially the same as the distance of the latch magnets <NUM> from the axis A. Furthermore, in the example of <FIG> the stationary magnet <NUM> is offset in the first direction of rotation (e.g. the clockwise direction indicated by the curved arrow D) from the one of the latch magnets <NUM> that is closest to the stationary magnet <NUM> when the worm gear assembly <NUM> is brought into a rotational position where a selected one of the apertures <NUM> (e.g. the aperture 109a) is spatially aligned with the axis B. In the example of <FIG>, this offset is similar to and shares the purpose with that described in the foregoing with references to the example of <FIG>. In the example of <FIG> the arrangement of the magnets <NUM>, <NUM> with respect to position and/or orientation of their magnetic poles such that the desired repelling magnetic force is created may be provided e.g. by arranging them with respect to each other such that the same magnetic poles of the stationary magnet <NUM> and the latch magnet <NUM> that is brought into proximity thereof are facing each other. As an example, this may be provided, for example, by arranging the stationary magnet <NUM> such that a predefined one of its magnetic poles (e.g. the north pole) is facing the worm gear assembly <NUM> and arranging each of the latch magnets <NUM> such that said predetermined one of the magnetic poles therein (e.g. the north pole) is facing the stationary magnet <NUM>.

Herein, the example of <FIG> is provided as a variation of the example of <FIG>. Similar modification with respect to the position of the stationary magnet <NUM> in relation to the latch magnets <NUM> is, however, equally applicable to the specific examples of <FIG> and to the general approach for arranging the magnets <NUM>, <NUM> with respected to each other illustrated via the examples of <FIG> as well.

Throughout the examples of <FIG>, the collimator plate <NUM> as well as other parts of the worm gear assembly <NUM> apart from the latch magnets <NUM> are made of a suitable non-magnetic material, e.g. a non-magnetic metal or metal alloy. As non-limiting examples in this regard, the collimator plate <NUM> and/or other parts of the worm gear assembly <NUM> (apart from the latch magnets <NUM>) may be made of brass or non-magnetic (e.g. austenitic) stainless steel.

<FIG> schematically illustrates a further variation of the magnet arrangement, again using the specific example of <FIG> as a basis. <FIG> schematically illustrates a worm gear assembly <NUM> that is similar to the worm gear assembly <NUM> of <FIG> as part of a collimator assembly where the stationary magnet <NUM> has been replaced with a stationary magnetic element <NUM> that is arranged in a fixed position with respect to the worm gear assembly <NUM>. Throughout this disclosure, the term "magnetic element" is employed to denote an element that is attracted by a magnet but that is not a magnet itself. In the example of <FIG> the exact position/orientation of the latch magnets <NUM> with respect to their magnetic poles does not play a significant role since they serve to attract the magnetic element <NUM> brought into proximity thereof regardless of the orientation of its magnetic poles with respect to the magnetic element <NUM>. The magnetic element <NUM> and the plurality of the latch magnets <NUM> may be jointly referred to as a magnet arrangement, whereas the magnetic element <NUM> and the plurality of the latch magnets <NUM> may be referred to as components of the magnet arrangement.

In the example illustrated in <FIG>, the arrangement of the latch magnets <NUM> in the worm gear assembly <NUM> is the same described for their arrangement in the worm gear assembly <NUM> in the foregoing with references to the example illustrated in <FIG>. The magnetic element <NUM> is positioned in the same or substantially the same plane with the worm gear assembly <NUM> outside the perimeter of the worm gear assembly <NUM>. The magnetic element <NUM> and the plurality of latch magnets <NUM> may be jointly referred to as a magnet arrangement.

<FIG> illustrates a curved arrow D that denotes the first direction of rotation, which also in this example is the clockwise direction. <FIG> further illustrates the line C that extends in a radial direction from the position of the axis A via the position of the axis B, while the magnetic element <NUM> is offset from the (conceptual) line C in a direction opposite to the first direction of rotation. Herein, the worm drive may be employed to rotate the worm gear assembly <NUM> to bring the desired one of the apertures <NUM> (in this example the aperture 109a) into a position where its center is spatially aligned with the axis B. The rotation may be in the first direction of rotation or opposite to the first direction of rotation. Without the arrangement of the magnetic element <NUM> and the latch magnets 108a the backlash would allow a small further rotational movement of the worm gear assembly <NUM> (e.g. in the clockwise direction), which in turn would result in misalignment between the aperture 109a and the axis B. However, in the example illustrated in <FIG> the attracting magnetic force between the magnetic element <NUM> and the latch magnet 108a pulls the worm gear assembly <NUM> opposite to the first direction of rotation (e.g. in the counter-clockwise direction) to prevent the further rotational movement that would be otherwise allowed by the backlash, thereby keeping the aperture 109a spatially aligned with the axis B.

In an exemplifying variation of the arrangement of <FIG>, the magnet arrangement may be modified such that the magnetic element <NUM> is replaced with the stationary magnet <NUM> and arranging the stationary magnet and the latch magnets <NUM> with respect to each other such that they provide an attracting magnetic force between the stationary magnet <NUM> and one of the latch magnets <NUM> brought into proximity thereof, which magnetic force serves to push the worm gear assembly <NUM> opposite to the first direction of rotation (e.g. in the counter-clockwise direction) to prevent the further rotational movement that would be otherwise allowed by the backlash. In this variation of the example of <FIG> such an arrangement of the magnets <NUM>, <NUM> with respect to position and/or orientation of their magnetic poles may be provided e.g. by arranging the magnets <NUM>, <NUM> with respect to each other such that the opposite magnetic poles of the stationary magnet <NUM> and the latch magnet <NUM> that is brought into proximity thereof are facing each other. As an example, this may be provided, for example, by arranging the stationary magnet <NUM> such that a predefined one of its magnetic poles (e.g. the north pole) is facing the worm gear assembly <NUM> and arranging each of the latch magnets <NUM> such that the opposite one of its poles (e.g. the south pole) is facing the stationary magnet <NUM> when brought into proximity of the stationary magnet <NUM>. As an example, this may be provided e.g. by arranging the stationary magnet <NUM> such that a predefined one of its poles (e.g. the north pole) is facing the worm gear assembly <NUM> and arranging the latch magnets <NUM> such that the opposite one of its poles (e.g. the south pole) is facing the outer perimeter of the worm gear assembly <NUM>.

<FIG> schematically illustrates a further variation of the magnet arrangement, again using the specific example of <FIG> as a basis. <FIG> schematically illustrates a worm gear assembly <NUM> that is similar to the worm gear assembly <NUM> of <FIG> in an arrangement where the plurality of latch magnets <NUM> is replaced with the corresponding plurality of magnetic elements <NUM> that are arranged to surround the collimator plate <NUM> in respective fixed positions with respect to the collimator plate <NUM> and the apertures <NUM> therein. The stationary magnet <NUM> and the plurality of the magnetic elements <NUM> may be jointly referred to as a magnet arrangement, whereas the stationary magnet <NUM> and the plurality of the magnet elements <NUM> may be referred to as components of the magnet arrangement.

In the example illustrated in <FIG>, the arrangement of the magnetic elements <NUM> in the worm gear assembly <NUM> is the same as the arrangement of latch magnets <NUM> described in the foregoing for the worm gear assembly <NUM>, whereas the stationary magnet <NUM> is positioned in the same manner as described in the foregoing for the magnetic element <NUM>. In this example, the exact position/orientation of the stationary magnet <NUM> with respect to its magnetic poles does not play a significant role since it serves to attract the magnetic element <NUM> brought into proximity thereof regardless of the orientation of its magnetic poles with respect to said magnetic element <NUM>.

Hence, the worm drive may be employed to rotate the worm gear assembly <NUM> to bring the desired one of the apertures <NUM> (in this example the aperture 109a) into a position where it is spatially aligned with the axis B. Without the arrangement of the stationary magnet <NUM> and the magnetic element 208a the backlash would allow a small further rotational movement of the worm gear assembly <NUM> (e.g. in the clockwise direction), which in turn would result in misalignment between the aperture 109a and the axis B. However, the attracting magnetic force between the stationary magnet <NUM> and the magnetic element 208a pulls the worm gear assembly <NUM> opposite to the first direction of rotation (e.g. in the counter-clockwise direction) to prevent the further rotational movement that would be otherwise allowed by the backlash, thereby keeping the center of the aperture 109a spatially aligned with the axis B.

The examples of <FIG> and <FIG> are provided as respective variations of the example of <FIG>. Similar modifications with respect to the components of the magnet arrangement are, however, equally applicable to the specific examples of <FIG> and to the general approach for providing the magnet arrangement illustrated via the examples of <FIG> as well. Moreover, the position of the magnetic element <NUM> in relation to the latch magnets <NUM> or the position of the stationary magnet <NUM> in relation to the plurality of magnetic elements <NUM> may be varied as described in the foregoing with references to the example illustrated in <FIG> for the arrangement of the stationary magnet <NUM> and the latch magnets <NUM>.

In the foregoing, a plurality of magnet arrangements where a plurality of magnet arrangement components is arranged in the worm gear assembly <NUM>, <NUM>, <NUM> and where a single stationary component of the magnet arrangement is provided outside the worm gear assembly <NUM>, <NUM>, <NUM> in a fixed position with respect thereto are described via a number of examples. In further examples the distribution of the magnet arrangement components may be varied in such a manner that the worm gear assembly <NUM>, <NUM>, <NUM> is provided with a single magnet arrangement component (e.g. a magnet) while the plurality of magnet arrangement components (e.g. a plurality of latch magnets) are provided outside the worm gear assembly <NUM>, <NUM>, <NUM> in respective fixed position with respect thereto.

As an example in this regard, <FIG> schematically illustrates such variation basing on the example of <FIG>, wherein the collimator plate <NUM> having the plurality apertures <NUM> that are different in size and/or shape arranged therein is provided with a single magnet <NUM> arranged at or close to the perimeter of the worm gear assembly <NUM> in a fixed position with respect to the collimator plate <NUM> and the apertures <NUM> therein. The magnet <NUM> may be secured in its position by using the frame ring <NUM> having the magnet <NUM> arranged therein or by using other suitable structure for fixing the magnet <NUM> into the worm gear assembly <NUM>. A plurality of stationary latch magnets <NUM> are positioned in respective fixed positions with respect to the worm gear assembly <NUM> in the same or substantially the same plane with the worm gear assembly <NUM> outside the perimeter of the worm gear assembly <NUM>. In the example of <FIG> the magnet <NUM> and the stationary latch magnets <NUM> are arranged with respect to each other such that a repelling magnetic force between the magnet <NUM> and one of the latch magnets <NUM> when the magnet <NUM> is brought into proximity thereof is created. Such an arrangement of the magnets <NUM>, <NUM> may be provided e.g. by arranging them with respect to each other such that the same magnetic poles of the latch magnet <NUM> and the magnet <NUM> brought into proximity thereof are facing each other. In the example of <FIG> this may be provided e.g. by arranging the stationary latch magnets <NUM> such that a predefined one of their poles (e.g. the north pole) is facing the worm gear assembly <NUM> and arranging the magnet <NUM> in the worm gear assembly <NUM> such that the predetermined one of its poles (e.g. the north pole) is facing the outer perimeter of the worm gear assembly <NUM> The magnet <NUM> and the plurality of stationary latch magnets <NUM> may be jointly referred to as a magnet arrangement, whereas the magnet <NUM> and the plurality of latch magnets <NUM> may be referred to as components of the magnet arrangement.

For graphical clarity of the illustration, <FIG> explicitly indicates only two of the apertures 109a, 109b with dedicated reference designators, while the illustration shows eight apertures <NUM> in total. Similarly, only two of the stationary latch magnets 405a, 405b are explicitly indicated using dedicated reference designators, while the illustration shows eight stationary latch magnets <NUM> in total. <FIG> also illustrates the line C that extends in a radial direction from the position of the axis A via the position of the axis B. In the example of <FIG>, the magnet <NUM> is aligned in a radial direction with the aperture 109a (i.e. positioned along the line C at or close to the outer perimeter of the worm gear assembly <NUM>), whereas the stationary latch magnet 405a is offset from the (conceptual) line C in the first direction of rotation, which in the illustration of <FIG> is the clockwise direction, also indicated by the curved arrow D, the stationary latch magnet 405a and the aperture 109a hence forming a magnet-aperture pair in this example. Similarly, another magnet-aperture pair of this example is formed by the stationary latch magnet 405b and the aperture 109b, while similar pairing is found also for the remaining pairs of a stationary latch magnet <NUM> and the aperture <NUM>.

The worm drive may be employed to rotate the worm gear assembly <NUM> to bring the desired one of the apertures <NUM> (in the example of <FIG> the aperture 109a) into a position where it is spatially aligned with the axis B. Without the arrangement of magnets <NUM> and 405a the backlash would allow a small further rotational movement of the worm gear assembly <NUM> (e.g. in the clockwise direction), which in turn would result in misalignment between the aperture 109a and the axis B. However, in the example illustrated in <FIG> the repelling magnetic force between the magnet <NUM> and the stationary latch magnet 405a that have the same magnetic polarity serve to provide a retraction force that pushes the worm gear assembly <NUM> into a second direction of rotation that is the opposite of the first direction of rotation (e.g. in the counter-clockwise direction) to prevent the further rotational movement that would be otherwise allowed by the backlash, thereby keeping the aperture 109a spatially aligned with the axis B.

While the example of <FIG> is provided as a modification of the magnet arrangement of the example of <FIG>, a corresponding modification is readily applicable to any of the other examples described in the foregoing, e.g. those illustrated in <FIG>.

Throughout the examples described in the foregoing, the characteristics of the magnets <NUM>, <NUM>, <NUM>, <NUM> and/or the magnetic elements <NUM>, <NUM> are chosen such that the repelling or attracting magnetic force arising from the magnet arrangement that serves to push or pull the worm gear assembly <NUM>, <NUM>, <NUM>, <NUM> against the first direction of rotation is sufficient to prevent free rotational movement of the worm gear assembly <NUM>, <NUM>, <NUM>. <NUM> from occurring while it is not strong enough to cause the worm gear assembly <NUM>, <NUM>, <NUM>, <NUM> rotating the worm screw <NUM>. Each of the magnets <NUM>, <NUM>, <NUM>, <NUM> may be provided as a respective permanent magnet, such as a neodymium magnet. Alternatively, at least some of the magnets <NUM>, <NUM>, <NUM>, <NUM> may be provided as respective electromagnets. Each of the magnetic elements <NUM>, <NUM> may be provided as a respective suitable piece of ferromagnetic or ferrimagnetic material, such as iron, cobalt, nickel or an alloy including iron, cobalt or nickel. Throughout the examples depicted in <FIG> the magnets <NUM>, <NUM>, <NUM>, <NUM> and/or the magnetic elements <NUM>, <NUM> are schematically illustrated in order to provide non-limiting examples of relative positions of the magnets <NUM>, <NUM>, <NUM>, <NUM> and/or the magnetic elements <NUM>, <NUM> with respect to each other and/or to the apertures <NUM> of the collimator plate <NUM>. Hence, the illustrations of <FIG> in this regard do not suggest any specific shape of the magnets <NUM>, <NUM>, <NUM>, <NUM> and/or the magnetic elements <NUM>, <NUM>.

In the foregoing, the examples throughout <FIG> make use of the collimator plate <NUM> having eight apertures <NUM> with evenly distributed angular spacing. This, however, is a non-limiting example and different number and/or arrangement of apertures may be employed instead. For example, the collimator plate <NUM> may include less than eight apertures <NUM> (any number in the range from two to seven, e.g. four or six) or the collimator plate <NUM> may include more than eight apertures <NUM> (e.g. ten, twelve or sixteen). Additionally or alternatively, the apertures <NUM> may disturbed in the angular direction in a non-uniform manner with the latch magnets <NUM> (or the magnetic elements <NUM>) arranged to surround the collimator plate <NUM> positioned accordingly to ensure appropriate magnetic push or pull when the center of the desired one of the apertures <NUM> is brought to a rotational position where it is spatially aligned with the axis B.

The size of the collimator plate <NUM> and the worm gear assembly <NUM>, <NUM>, <NUM>, <NUM> as well as the number of apertures <NUM> arranged in the collimator plate <NUM> may be selected in accordance with characteristics and/or requirements of the X-ray spectrometer device making use of the collimator assembly <NUM>. As a non-limiting example, the apertures <NUM> may be provided as circular or rectangular apertures that have a diameter or a diagonal, respectively, in a range from a few ten micrometers to a few hundred micrometers. As a non-limiting example concerning the size of the worm gear assembly <NUM>, <NUM>, <NUM>, <NUM>, it may have a diameter in a range from a few centimeters to approximately <NUM> centimeters.

Claim 1:
A collimator assembly (<NUM>) for an X-ray spectrometer device, the collimator assembly (<NUM>) comprising
a rotatable gear assembly (<NUM>, <NUM>, <NUM>, <NUM>) comprising a worm gear assembly and including a collimator plate (<NUM>) having a plurality of apertures (<NUM>) of different size and/or shape arranged therein;
a driving assembly (<NUM>, <NUM>) comprising a worm screw (<NUM>) for rotating the gear assembly (<NUM>, <NUM>, <NUM>, <NUM>) and an electric motor for rotating the worm screw (<NUM>) to bring the gear assembly (<NUM>, <NUM>, <NUM>, <NUM>) into a rotational position where a selected one of the plurality of apertures (<NUM>) is spatially aligned with a predefined axis (B) along which a collimated X-ray beam is to be provided from the X-ray spectrometer device; and
a magnet arrangement (<NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>) for generating a magnetic force that is arranged to push or pull the gear assembly (<NUM>, <NUM>, <NUM>, <NUM>) into a predefined direction of rotation to prevent rotational movement due to backlash, thereby keeping the selected one of the plurality of apertures (<NUM>) spatially aligned with said predefined axis (B).