Patent Description:
Some detectors operate by "inhaling" a stream of fluid, such as air, into a detector inlet and sampling that air with an analytical apparatus to detect substances of interest. That inhaled stream of air can be sampled from the detector inlet using a sampling inlet such as a pinhole, capillary or membrane inlet.

Often, hand held, or portable devices may be needed for example for use by military and security personnel. These personnel frequently operate in hostile environments in the presence of large quantities of dust and grit and other particulate matter. Such particulates may obstruct the sampling inlet, or otherwise damage the detector. In some cases, particulates carried by the stream of air may comprise substances to which the detector is sensitive. If these accumulate in a detector or its inlets they may contaminate the detector, and may cause recovery time issues. <CIT> gives an examples of a sampling device having a shield for depleting the sample inlet from particles. <CIT> discloses a mass spectrometer analyser having a pinhole sample inlet.

Optional features are set out in the appended dependent claims.

Embodiments of the disclosure will now be discussed, by way of example only, with reference to the accompanying drawings, in which:.

In the drawings like reference numerals are used to indicate like elements.

Embodiments of the disclosure relate to detectors for detecting substances of interest, and to detector inlets arranged to obtain samples for analysis in the detectors.

To obtain a sample, a fluid can be inhaled into a detector inlet and flowed to an outlet along a flow passage. A sampling inlet is coupled to the flow passage to provide samples of the fluid to an analytical apparatus. Where particulates are present in the environment they are carried by the inhaled flow, and are spatially distributed throughout it. Embodiments of the disclosure aim to direct the flow of fluid with a flow director that varies this spatial distribution of particulates. This provides a volume of the flow passage, downstream of the flow director, in which the spatial distribution of particulates is depleted. The sampling inlet can be arranged to obtain samples from this depleted sampling volume to reduce the risk of contaminating the detector with unwanted particulate material, or simply blocking the sampling inlet.

This modification of the distribution of particulates may be achieved, for example, by speeding up, slowing down, or changing the direction of at least a part of the fluid flow along the flow passage.

<FIG> shows a detector <NUM> comprising a detector inlet <NUM>, coupled to an analytical apparatus <NUM> by a sampling inlet <NUM>, such as a pinhole, capillary or membrane inlet, and a sampler <NUM> arranged to obtain samples of the fluid via the sampling inlet <NUM> from a sampling volume <NUM> around the sampling inlet <NUM>.

The detector inlet <NUM> shown in <FIG> comprises a flow passage <NUM> for carrying a flow of fluid <NUM> past the sampling inlet <NUM>. As illustrated the detector inlet <NUM> of <FIG> comprises a flow provider <NUM> arranged to flow the fluid into the flow passage, past the sampling inlet <NUM>, and along the flow passage <NUM> to an outlet. The detector inlet <NUM> may also comprise a heater <NUM> which may be arranged to heat the flow of fluid <NUM> upstream of the sampling inlet <NUM>.

The flow passage <NUM> comprises a flow director <NUM> which, in the example of <FIG>, is provided by a bend in the flow passage <NUM> arranged to change the direction of the fluid flow upstream from the sampling inlet <NUM>.

The sampling inlet can be coupled to the flow passage <NUM> and adapted for collecting samples of the fluid from a sampling volume <NUM> in the flow passage <NUM> around the sampling inlet <NUM>. The sampler <NUM> is configured to draw a selected volume of fluid, smaller than the sampling volume <NUM>, through the inlet to provide a sample to the analytical apparatus. The sampler <NUM> may comprise an electromechanical actuator, for example a solenoid driven actuator, and/or a mechanical pump arranged to transfer vapour from the sampling volume <NUM>, through the sampling inlet <NUM> and into the analytical apparatus.

The analytical apparatus <NUM> shown in <FIG> comprises a mass spectrometer. A mass spectrometer may comprise an ioniser, an ion accelerator, a beam focusser, a magnet, and a faraday collector arranged to perform mass spectrometry analysis on samples of vapour. As illustrated, a controller <NUM> is coupled to control the analytical apparatus, the flow provider, the heater, and the sampler. The controller <NUM> may comprise a processor and a memory storing instructions for operation of the detector <NUM>.

In operation of the embodiment illustrated in <FIG>, the flow provider <NUM> flows fluid along the flow passage, and the bend in the flow passage <NUM> changes the direction of the fluid flow upstream from the sampling inlet <NUM>. By directing the flow in this way, the spatial distribution of particulates across the fluid flow can be changed to increase a proportion of the particulates which flow past the sampling inlet <NUM> without entering a volume around the sampling inlet <NUM>. In the example shown in <FIG> this occurs because the inlet is arranged on the inside of the bend, and particulates carried by the flow tend to flow along the outside of the bend, away from the sampling inlet <NUM>. This change in distribution is illustrated in Inset A of <FIG>. Inset A illustrates a plot <NUM> of a spatial distribution of particulates along the line A, the horizontal axis indicates position across the direction of flow of the fluid. The plot <NUM> shown in Inset A of <FIG> corresponds to a spatial distribution of particulates upstream from the flow director <NUM>. Inset B illustrates a plot <NUM> of a spatial distribution of particulates along the line B, across the direction of flow of the fluid in the region of the sampling volume <NUM>. From a comparison of Inset A and Inset B, it can be seen that the spatial distribution of particulates across the flow of fluid <NUM> is changed to increase the relative proportion of the particulates carried past the sampling inlet <NUM> along the flow passage <NUM> without entering the sampling volume <NUM>.

The controller <NUM> can control the sampler <NUM> to draw a sample from the sampling volume <NUM> and to provide the sample to the analytical apparatus <NUM>. The analytical apparatus <NUM> illustrated in <FIG> can then analyse the sample by performing mass spectrometry on the sample.

As will be appreciated, the detector inlet <NUM> of the present disclosure may also be used in other kinds of detectors such as, detectors comprising ion mobility spectrometers, time of flight ion mobility spectrometers, chromatography apparatus and other kinds of analysers for detecting substances of interest.

<FIG> shows a detector <NUM> in which the analytical apparatus comprises an ion mobility spectrometer <NUM>' but which is otherwise identical to the apparatus shown in <FIG>. The ion mobility spectrometer of <FIG> is coupled to a detector inlet <NUM> by a sampling inlet <NUM>. A sampler <NUM> is arranged to obtain samples of the fluid through the sampling inlet <NUM> and to provide them to the ion mobility spectrometer <NUM>'. As in the example of <FIG>, the controller <NUM> may comprise a processor and a memory storing instructions for operation of the detector <NUM>. Also as in <FIG>, the sampler <NUM> may comprise an electromechanical actuator, for example a solenoid driven actuator, and/or a mechanical pump arranged to transfer vapour from the sampling volume <NUM> through the sampling inlet <NUM> into the analytical apparatus.

In <FIG>, the ion mobility spectrometer <NUM>' may comprise a reaction region <NUM> in which a sample can be ionised by an ioniser <NUM>. The sampler <NUM> can be operated to obtain a sample from the sampling volume <NUM> through the sampling inlet <NUM>, and to provide the sample to the reaction region <NUM>. Some examples of sampling inlets <NUM> include 'pinhole' inlets, which may be approximately <NUM> in diameter, for example the diameter may be at least <NUM>, for example at least <NUM>, for example less than <NUM>, for example less than <NUM>.

A gate electrode <NUM> may separate the reaction region <NUM> from a drift chamber <NUM>. The gate electrode <NUM> may comprise an assembly of at least two electrodes, which may be arranged to provide a Bradbury-Nielsen gate. The drift chamber <NUM> can comprise a collector <NUM> toward the opposite end of the drift chamber <NUM> from the gate electrode <NUM> for detecting ions. The drift chamber also comprises a drift gas inlet <NUM>, and a drift gas outlet <NUM> arranged to provide a flow of drift gas along the drift chamber <NUM> from the ion collector <NUM> towards the gate <NUM>. The sampler <NUM> can be operated by the controller <NUM> to obtain fluid from sampling volume <NUM> through the sampling inlet <NUM>. The sampler <NUM> can also be operated to provide an obtained sample into the reaction region <NUM> of the spectrometer <NUM>'. The reaction region shown in <FIG> comprises an ioniser <NUM> for ionising a sample. The ioniser <NUM> may comprise a corona discharge ioniser. The drift chamber <NUM> may comprise drift electrodes <NUM>, <NUM> for applying an electric field along the drift chamber <NUM> to move ions towards the collector <NUM> against the flow of the drift gas. Although the apparatus of <FIG> is illustrated as comprising two drift electrodes <NUM>, <NUM>, some embodiments may comprise more than two drift electrodes.

In operation, the flow provider <NUM> can be operated to direct a flow of fluid <NUM> past the flow director <NUM> in the flow passage <NUM> and then past the sampling inlet <NUM>. As the fluid flows past the flow director <NUM> the change in direction it provides varies the distribution of particulates transverse to the direction of flow of the fluid relative to the shape of said distribution upstream of that bend. This may provide a depleted region of the cross section of the flow passage <NUM> through which relatively few particulates flow, the majority of the particulates being carried through other parts of the cross section of the flow passage. This depleted region may persist for a distance along the flow passage <NUM> thereby defining a sampling volume <NUM> in which the number (e.g. count per unit volume) of particulates is relatively lower than in other regions of the flow passage.

The sampler <NUM> can be operated to obtain a sample of fluid from this sampling volume <NUM> via the sampling inlet <NUM>. The obtained sample of fluid can then be provided to an analytical apparatus. In the example of <FIG> the analytical apparatus comprises an ion mobility spectrometer <NUM>'.

As explained above, detector inlets of the present disclosure find particular application in portable devices which may be used in hostile environments where dust and contaminants are prevalent. These detector inlets may be used with a variety of analytical apparatus, such as the mass spectrometer of <FIG> and the ion mobility spectrometer of <FIG>, other kinds of analysers, spectrometers and/or chromatography apparatus. In addition, the detector inlet <NUM> may have different configurations.

As shown in <FIG>, <FIG>, and <FIG>, a detector inlet <NUM> may comprise flow directors having different structural forms. Each of these flow directors may vary the distribution of particulates in the flow of fluid <NUM> to provide a sampling volume <NUM> having a relatively lower concentration of particulates (e.g. a lower mass per unit volume, or particulate count per unit volume). In some embodiments the flow director <NUM> may provide a sampling volume <NUM> where fluid flow is slow compared to the flow of fluid <NUM> past the sampling volume <NUM> along the flow passage. This may be achieved by providing a region of slow flow, and/or by accelerating part of the flow.

Accelerating may comprise changing the direction of at least a part of the flow of fluid <NUM> or increasing its speed, or both. Providing a region of slow flow may comprise providing a culvert or recess or other sheltered region as in <FIG>.

<FIG> shows an example of a detector inlet <NUM> comprising a flow director, a sampling inlet <NUM>, and a flow passage. <FIG> comprises three views of the detector inlet <NUM>, <FIG> shows a section view of the detector inlet <NUM> from the line indicated as X-X in <FIG> shows a section view of the detector inlet <NUM> from the line indicated as Y-Y in <FIG> shows a section view of the detector inlet <NUM> from the line indicated as Z-Z in <FIG>.

As can be seen in <FIG>, in the embodiment illustrated in <FIG> the flow director <NUM> protrudes into the flow passage <NUM> from a wall of the flow passage. The flow director <NUM> can direct the flow of fluid to flow only to one side of the flow director. The flow director <NUM> may protrude further into the flow passage <NUM> toward the flow director's downstream end than towards its upstream end. For example, the flow director <NUM> may have a sloped surface, which may be straight, curved or graduated, to provide a ramp. As illustrated in <FIG>, the sampling inlet <NUM> may be disposed downstream of the flow director <NUM> to obtain samples from a sheltered sampling volume <NUM>. The speed of the fluid flow in the sampling volume <NUM> may be lower than the speed of fluid flow past the sampling volume <NUM>. The speed of the fluid flow past the sampling volume <NUM> may be higher than the speed of the fluid flow upstream from the flow director.

<FIG> illustrates one example of a spatial distribution of particulates across the flow passage <NUM> upstream from the flow director. As can be seen in <FIG>, upstream from the flow director, particulates carried by the fluid flow may be distributed relatively evenly across the width of the flow. As will be appreciated in the context of the present disclosure, the distribution shown in <FIG> is merely exemplary and may be different in different conditions, for example, gravity may skew the distribution in one direction or another depending on the orientation of the device. As illustrated in <FIG>, downstream from the flow director, the spatial distribution of particulates across the direction of flow of the fluid may be modified by the flow director. For example, as illustrated in <FIG> the spatial distribution of particulates may be more uneven downstream from the flow director <NUM> than upstream from it. As shown in <FIG>, downstream from the flow director the particulates are more concentrated outside the sampling volume than within it. As a result of this unevenness in the distribution, particulates may be more likely to flow past the inlet without entering the sampling volume <NUM>.

<FIG> shows another example of a flow director. <FIG> comprises three views of a detector inlet <NUM>, <FIG> shows a section view of the detector inlet from the line indicated as X-X in <FIG> shows a section view of the detector inlet <NUM> from the line indicated as Y-Y in <FIG> shows a section view of the detector inlet <NUM> from the line indicated as Z-Z in <FIG>.

As can be seen from <FIG>, the flow director <NUM> may be arranged to separate the fluid flow into at least two separate flow paths, separated by the flow director. For example the flow director <NUM> of <FIG> may be arranged mid-flow, spanning across the flow passage, and coupled to two walls of the flow passage. The flow director <NUM> shown in <FIG> may be tapered so that it is narrower towards its upstream end than it is towards its downstream end. As shown in <FIG>, the flow director <NUM> provides a sheltered sampling volume <NUM> at its downstream end, and the sampling inlet <NUM> may be arranged on the downstream end of the flow director. The passage of fluid flow on both sides of this flow director <NUM> may reduce the tendency of particles to accumulate around the sampling inlet <NUM>.

<FIG> illustrates one example of a spatial distribution of particulates across the flow passage <NUM> upstream from the flow director. The description of <FIG>, above, also applies to <FIG> illustrates a shape of a distribution of particulates across the direction of the fluid flow in the region of the sampling volume <NUM>. It can be seen from <FIG> that the flow director <NUM> can increase the probability that particulates will flow around the sampling volume <NUM>, rather than flowing through it.

<FIG> illustrates another example of a detector inlet. <FIG> comprises three views of a detector inlet, <FIG> shows a section view of the detector inlet <NUM> from the line indicated as X-X in <FIG> shows a section view of the detector inlet <NUM> from the line indicated as Y-Y in <FIG> shows a section view of the detector inlet <NUM> from the line indicated as Z-Z in <FIG>.

In <FIG>, the flow director <NUM> is provided by a variation in cross section of the flow passage. In this embodiment, the flow director <NUM> comprises a recess in a wall of the flow passage, and the sampling inlet <NUM> is arranged in the recess. For example, the sampling inlet <NUM> may be arranged in the upstream wall of the recess, so the flow can be directed away from the sampling inlet <NUM>. Accordingly, the fluid flow can be directed past the recess (and the sampling volume), thereby reducing the probability that particulates carried by the flow of fluid will enter the sampling volume <NUM>.

<FIG> illustrates one example of a spatial distribution of particulates across the flow passage <NUM> upstream from the flow director. The description of <FIG>, above, also applies to <FIG> illustrates the spatial distribution of particulates across the direction of the flow downstream of the flow director <NUM> where the flow passes the recess. <FIG> illustrates a lower number of particulates in the recess than in the fluid flowing past it, thereby illustrating one way in which the shape of the spatial distribution of particulates may be changed by a flow director. It can be seen in <FIG> that, where the flow director <NUM> comprises a recess, and in some other examples, total width and/or shape of the flow passage <NUM> may be changed by a flow director, so although part of the distribution of particulates may be relatively unchanged the shape of the distribution is still different from its shape upstream of the flow director.

<FIG> shows another example of a flow director. In the example of <FIG> the flow director <NUM> comprises a series of foils <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>. The foils, <NUM>-<NUM>, may be ring shaped and may be arranged on a common axis. Each foil <NUM>-<NUM>, may have an aerofoil type profile, or be otherwise configured, for example by being shaped, profiled and/or angled, to funnel particulates inside the foils in preference to fluid. In an embodiment the foils <NUM>-<NUM> may be configured, for example by being shaped, profiled and/or angled, to preferentially direct fluid flow outside of the foils.

The foils <NUM>-<NUM> may be spaced apart in the direction of flow of the fluid. At the upstream end of this flow director <NUM>, one of the foils <NUM> may span most or all of the width of the flow passage. The span of the downstream foils <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM> may become successively smaller, to provide a tapered structure. Each of the foils may be pitched (e.g. at an acute angle) relative to the direction of flow of the fluid along the flow passage <NUM>. The foils may all have the same pitch, or the pitch may be varied. The foil <NUM> at the downstream end of the flow director may be smaller than the other foils. The sampling inlet <NUM> illustrated in <FIG> is arranged to obtain samples of fluid from a sampling volume <NUM> downstream from this last, most downstream, foil in the series of foils. The foils may be heated to inhibit the accumulation of substances on the foils, and/or to vapourise aerosols carried by the flow of air along the detector inlet.

Although they are described as being rings, the foils of course need not be circular rings and may be non-circular, for example oval, tapered, rectangular, square or any other shape. The foils may be arranged to be symmetrical about a common axis, for example an axis aligned with the direction of flow of fluid along the flow passage. For example, one or more of the foils may be helical, or all of the circular foils may be replaced by a single helical foil. For example a helical foil may spiral inward along the flow passage so that it has a greater diameter at its upstream end than at its downstream end.

<FIG> illustrates one example of a spatial distribution of particulates across the flow passage <NUM> upstream from the flow director foils <NUM>-<NUM> of <FIG>. The description of <FIG>, above, also applies to <FIG> illustrates the spatial distribution of particulates across the direction of the flow downstream of the flow director foils <NUM>-<NUM> where the flow passes the inlet <NUM>. As shown in <FIG>, in this region, downstream from the foils <NUM>-<NUM>, the particulates are concentrated into a narrow region of the flow passage.

Some flow directors (e.g. for example those shown in <FIG>, <FIG>, and <FIG>) may provide a reduction in the cross section of the flow passage <NUM> through which the fluid can flow. In some embodiments, the flow director may cause a change in direction of the fluid flow which could cause undesirable concentration and/or deposition of particulates in a region of the flow passage.

<FIG> illustrates some embodiments of detector inlets in which the flow passage <NUM> comprises variations <NUM> in the shape and/or area of its cross section to accommodate changes in flow caused by the flow director <NUM>. These variations <NUM> in cross section may be arranged at least partially downstream of the flow director <NUM>, for example at least part of the variation <NUM> in cross section may be arranged downstream from the upstream end of the flow director <NUM>. For example these variations in cross section may be configured to promote laminar flow of fluid past the flow director. In some embodiments the variations comprise a bulge in at least one wall of the flow passage. The bulge may comprise curved, sloped or graduated portions arranged to accommodate variations in fluid flow caused by the flow director.

Claim 1:
A detector comprising:
an analytical apparatus (<NUM>) for detecting a substance of interest, and
a detector inlet (<NUM>), the detector inlet (<NUM>) comprising:
a flow conduit (<NUM>) for carrying a flow of fluid provided by a flow provider, the flow conduit (<NUM>) comprising a sampling volume (<NUM>);
and a flow director (<NUM>) arranged to vary a spatial distribution of particulates transverse to the direction of flow of the fluid relative to the shape of said distribution upstream of the flow director (<NUM>) to provide a depleted region of the cross section of the flow conduit (<NUM>) through which relatively few particulates flow, while the majority of the particulates are carried through other parts of the cross section of the flow conduit (<NUM>), the depleted region defining the sampling volume (<NUM>);
a sampling inlet (<NUM>) adapted to collect samples of the fluid from the sampling volume as the fluid flows past the sampling inlet (<NUM>), and to provide the samples to the analytical apparatus, wherein the flow of fluid carries particulates;
the detector is characterized in that the sampling inlet (<NUM>) comprises at least one of a pinhole inlet, a membrane inlet, and a capillary inlet and the flow director (<NUM>) is provided by a bend in direction of the flow conduit (<NUM>).