WO2017196924A1

WO2017196924A1 - Compact, low component count xrf apparatus

Info

Publication number: WO2017196924A1
Application number: PCT/US2017/031880
Authority: WO
Inventors: Zewu Chen; John H. Burdett; Joseph SPINAZOLA; Rory Delaney; Seth MADISON
Original assignee: X-Ray Optical Systems, Inc.
Priority date: 2016-05-10
Filing date: 2017-05-10
Publication date: 2017-11-16

Abstract

An x-ray engine apparatus, including a sample cell carriage for inserting and removing a sample cell to and from a focal area of an x-ray engine, wherein adequate x-ray containment surfaces are included along the surfaces and path of the carriage to contain x-rays from emanating during insertion and removal; and/or wherein an x-ray shutter is automatically engaged by the carriage to contain x-rays from emanating during insertion and removal. The sample cell is insertable and removable from the sample cell carriage by a user, during which x-rays remain contained. In one embodiment, incident x-rays are focused to the measurement focal area in the engine at a low angle of incidence (e.g., 20-25 degrees or less) to thereby allow a detector to be located close to the measurement focal area (e.g., 5mm) without substantially blocking the incident x-rays.

Description

COMPACT, LOW COMPONENT COUNT XRF APPARATUS

Cross-Reference to Related Application

[0001] This application claims the benefit of United States provisional patent application Serial No. 62/334, 105, filed May 10, 2016, which is hereby incorporated herein by reference in its entirety.

Technical Field

[0002] This invention relates in general to apparatus and methods used for analysis of samples. More particularly, the present invention is directed to a Compact, Low Component Count X-Ray Fluorescence ("XRF") Apparatus.

Background of the Invention

[0003] X-ray analysis of samples is a growing area of interest across many industries such as consumer products, medical, pharmaceutical, environmental, and petroleum. The use of x-ray fluorescence, x-ray diffraction, x-ray spectroscopy, x-ray imaging, and other x-ray analysis techniques has led to a profound increase in knowledge in virtually all scientific fields.

[0004] X-ray fluorescence (XRF) is an analytical technique by which a substance is exposed to a beam of x-rays to determine, for example, the presence of certain components. In XRF, at least some of the elemental constituents of the substance exposed to x-rays can absorb x-ray photons and produce characteristic secondary fluorescence. These secondary x- rays are characteristic of the elemental constituents in the substance. Upon appropriate detection and analysis these secondary x-rays can be used to characterize one or more of the elemental constituents. XRF techniques have broad applications in many chemical and material science fields, including water, environmental, industrial, medical, semiconductor chip evaluation, petroleum, and forensics, among others.

[0005] U.S. Patents Nos. 6,934,359 and 7,072,439, hereby incorporated by reference herein in their entirety and assigned to X-Ray Optical Systems, Inc., the assignee of the present invention, disclose monochromatic wavelength dispersive x-ray fluorescence (MWD XRF) techniques and systems for the analysis of liquid samples, e.g., for trace level measurement of sulfur in petroleum products. U.S. Patent No. 7,738,630, hereby incorporated by reference herein in its entirety and assigned to X-Ray Optical Systems, Inc., the assignee of the present invention, discloses monochromatic excitation, energy dispersive x-ray fluorescence (ME-EDXRF) techniques and systems for, e.g., for trace level

measurement of toxins in a variety of substances including water, petroleum products, and consumer products.

[0006] XRF testing can take place off-line, i.e., using a bench-top, laboratory-type instrument to analyze a sample. The material is removed from its source (e.g., for fuel, from a refinery or transportation pipeline) and then deposited in a sample chamber; or into a windowed sample cell which is then deposited into a chamber. Off-line, bench-top instruments conventionally need not meet any unusual operational / pressure / environmental / size / weight / space / safety constraints, but merely need to provide the requisite

measurement precision for a manually-placed sample. Moreover, off-line instruments can be easily maintained between measurements.

[0007] In contrast to off-line analysis, on-line analysis provides "real-time" monitoring of sample composition at various points in the manufacturing process. For example, all fuel products are subject to sulfur level compliance - requiring some variant of on-line monitoring during fuel refining and transportation in pipelines. On-line analysis of fuels in a refinery and in pipelines, however, requires consideration of numerous operational issues not generally present in an off-line, laboratory setting.

[0008] In-the-field analysis can be considered a combination of the off-line and on-line approaches above. This may involve deployment of a normally off-line, bench-top system, into the field to be closer to the sample, or in an operational environment where measurement is needed (e.g., refineries, ships, platforms). The demands on these systems (size, weight, cost, simplicity, reliability) are increasing.

[0009] What is required, therefore, is a small, low cost, simple and reliable XRF system suitable for in-the-field applications.

Summary of the Invention

[0010] The shortcomings of the prior art are overcome and additional advantages are provided by the present invention which in one aspect is an x-ray engine apparatus, including a sample cell carriage for inserting and removing a sample cell to and from a focal area of the x-ray engine, wherein adequate x-ray containment surfaces are included along the surfaces and path of the carriage to contain x-rays from emanating during insertion and removal; and/or wherein an x-ray shutter is automatically engaged by the carriage to contain x-rays from emanating during insertion and removal. The sample cell may be insertable and removable from the sample cell carriage by a user, during which x-rays remain contained. In one embodiment, incident x-rays are focused to the measurement focal area in the engine at a low angle of incidence (e.g., 20-25 degrees or less) to thereby allow a detector to be located close to the measurement focal area (e.g., 5mm) without substantially blocking the incident x- rays.

[0011] The engine apparatus may be used in combination with an x-ray analyzer, the x- ray analyzer including an x-ray engine with an x-ray excitation path and an x-ray detection path, wherein the x-ray excitation and/or the x-ray detection path defines the sample focal area.

[0012] The focal area may be a focal point, defined by focused x-rays to/from at least one focusing optic in the x-ray excitation path and/or the x-ray detection path. The focusing optic may be a curved diffracting optic or a polycapillary optic.

[0013] The system may comprise a monochromatic wavelength-enabled XRF analyzer; e.g., an MWDXRF or ME-EDXRF analyzer.

[0014] The sample may comprise a liquid, partial-liquid, granular mixed liquid/solid material (e.g., soil), or a solid (e.g., powder) sample requiring the measurement of an analyte therein, such as S, CI, P, K, Ca, V, Mn, Fe, Co, Ni, Cu, Zn, Hg, As, Pb, and Se.

[0015] The present invention is especially useful for measuring non-homogeneous samples, i.e., the present invention provides analyte measurement results for localized areas of the sample, as well as a measurement representative of the overall concentration of the analyte in a sample volume, despite the presence of localized inconsistencies in the sample.

[0016] Further, additional features and advantages are realized by the techniques of the present invention. Other embodiments and aspects of the invention are described in detail herein and are considered a part of the claimed invention. Brief Description of the Drawings

[0017] The subject matter regarded as the invention is particularly pointed out and distinctly claimed in the claims at the conclusion of the specification. The foregoing and other objects, features, and advantages of the invention are apparent from the following detailed description taken in combination with the accompanying drawings in which:

[0018] Fig. 1 is a functional block diagram of the elements of an

exemplary x-ray fluorescence system;

[0019] Fig.2 is a schematic view of an exemplary MWD XRF x-ray

engine useable with the sample scanning apparatus of the present invention.

[0020] Fig. 3 is a schematic view of an exemplary ME EDXRF x-ray

engine useable with the sample scanning apparatus of the present invention;

[0021] Fig. 4 is a perspective view of an x-ray engine in accordance

with one aspect of the present invention;

[0022] Figs. 5a-b are perspective views of the engine of Fig. 4

showing the operation of an exemplary sample cell carriage in

accordance with an aspect of the present invention;

[0023] Figs. 6a-b are partial, cross-sectional views of the x-ray engine

in accordance with an aspect of the present invention;

[0024] Fig. 7 shows an exemplary x-ray analyzer having an internal x- ray engine, in accordance with the present invention;

[0025] Fig. 8 is a perspective view of a sample cell carriage of another

exemplary sample cell carriage in accordance an aspect of the present invention; and

[0026] Figs. 9a-b are partial cross-sectional views of the carriage of

Fig. 8, in accordance with an aspect of the present invention. Detailed Description of the Invention

[0027] Fig. 1 is a functional block diagram of an exemplary XRF system 10 used for exposing a sample to x-ray radiation to produce fluorescent radiation which can then be detected and analyzed to determine a characteristic of the sample. The system may include an x-ray source 12, a first x-ray focusing device 14, a sample under test 16, a second x-ray focusing device 18, an x-ray detector 20, and analyzer components 32 for providing the analytical result. The x-ray source 12, for example, an x-ray tube, produces a beam of x-rays 22. Beam 22 may diffracted or focused by one or more x-ray focusing optics 14 as discussed further below.

[0028] When irradiated by beam 24, at least one of the constituents of sample in chamber 16 is excited in such a fashion that the constituent fluoresces, that is, produces a secondary source of x-rays 26 due to excitation by x-rays 24. Again, since x-ray beam 26 is typically a diverging beam of x-rays, beam 26 may be focused by the second x-ray focusing optics 18, for example, to produce a focused beam of x-rays 28 directed toward x-ray detector 20.

[0029] X-ray detector 20 may be a proportional counter- type or a semiconductor type x- ray detector (e.g., silicon drift detector), or any other suitable type of x-ray fluorescence detector known to one skilled in the art. Typically, x-ray detector 20 produces an electrical signal 30 containing a characteristic of the detected x-rays which is forwarded to analyzer components 32 for analysis, printout, or other display.

[0030] X-ray focusing devices / optics 14, 18 for advanced XRF systems, including those below, may include, for example, curved crystal monochromating optics such as those disclosed in commonly assigned U.S. patents 6,285,506; 6,317,483; 7,035,374 and 7,738,629; and/or polycapillary optics such as those disclosed in commonly assigned U.S. patents 5, 192,869; 5, 175,755; 5,497,008; 5,745,547; 5,570,408; and 5,604,353. Optic/source combinations such as those disclosed in commonly assigned U.S. Patents 7, 110,506;

7,209,545; and 7,257, 193 are also useable. Each of the above-noted patents is hereby incorporated herein by reference in its entirety.

[0031] The following are two examples of x-ray-optic-enabled analyzer engines which may be used in connection with the present invention: Exemplary MWD XRF X-Ray Analysis Engines:

[0032] The assignee of the present invention has previously disclosed a Monochromatic Wavelength Dispersive X-ray Fluorescence (MWD XRF) analyzer 80 using two

monochromating optic sets (U.S. Patents 6,934,359 and 7,072,439 - hereby incorporated by reference herein in their entirety), as shown schematically in Fig. 2. The related SINDIE (Sulfur IN DIEsel) and CLORA (chlorine) product lines for the measurement of e.g., sulfur and chlorine in diesel fuel and other petroleum products revolutionized XRF and provide many advantages including: (1) signal / background (S/B) is improved due to monochromatic excitation of the sample by DCC1 14', i.e., the bremsstrahlung photons with energies under fluorescence peaks (which normally swamp these peaks of interest) can only reach the detector through scattering, therefore improving the S/B ratio dramatically compared to polychromatic excitation; (2) superior energy resolution - this eliminates all common interference problems and provides the physical basis for upstream applications; (3) inherent robustness and low maintenance - the analysis engine is low power, compact, with no moving parts or consumable gasses; and (4) unprecedented dynamic range, e.g., a quantification level from 0.3ppm to 5% of sulfur in a sample.

[0033] The MWD XRF engine 80, shown schematically in Fig. 2, includes curved monochromating optics 14' and 18' in the excitation and detection paths respectively, forming focal area or point 43 on the sample 42 (discussed further below), which is the configuration of the SINDIE sulfur analyzer discussed above. However, an optic may only be present in one of these paths, which still requires precise alignment. In one example, an optic of any of the above-describe types may only be present in the excitation path, and the detection path would include an energy dispersive detector. This is the common

configuration of an energy dispersive x-ray fluorescence (EDXRF) system, discussed further below.

Exemplary ME EDXRF X-Ray Analysis Engine :

[0034] Monochromatic excitation, energy dispersive x-ray fluorescence (ME-EDXRF) analyzers can also be used for this application, in accordance with the present invention. The engine technology is disclosed in, e.g., commonly assigned US Patent No. 8,559,597 entitled XRF System Having Multiple Excitation Energy Bands In Highly Aligned Package, the entirety of which is hereby incorporated by reference herein. In one embodiment this engine 90 involves monochromatic excitation known as HD XRF as depicted schematically in Fig. 3. HD XRF is a multi -element analysis technique offering significantly enhanced detection performance over traditional ED or WD XRF. This technique applies state-of-the-art monochromating and focusing optics 14" illuminating a focal area or point 43 on the sample 42, enabling multiple select-energy excitation beams that efficiently excite a broad range of target elements in the sample. Monochromatic excitation dramatically reduces scattering background under the fluorescence peaks, greatly enhancing elemental detection limits and precision.

[0035] Figs. 4 and Figs. 5a-b are perspective views of an exemplary x-ray engine 100 in accordance with the present invention (where like reference numerals are used for like elements), used in combination with an exemplary XRF system of Fig. 7.

[0036] Summarizing with reference to Figs. 4-5, sample cell 142 can be placed into a sliding sample carriage 140 which accepts and slides the sample cell toward the focal area (not shown) inside engine, or can be slided outside of the engine (Fig. 5b) allowing insertion / removal of the sample cell 142. If adequate x-ray containment surfaces are included along the surfaces and path of carriage 140 (e.g., labyrinth j oints, interlocking surfaces, etc) the need for an electrical interlock system (a complex electro-mechanical system which ensures x-rays are diasbled when placing the sample) can be avoided thus increasing simplicity and decreasing costs. This carriage technique can make the engine "intrinsically safe" providing x-ray shielding without electro-mechanical interlocks or human intervention; and also thereby lowering part count. This also helps system reliability and stability by allowing the x-ray source to stay at a constant operating level, rather than cycling power.

[0037] Sample cell may be a pre-filmed, precision sample cell 142/242, including an outer body forming an interior sample reservoir, the top end of which accepts a sample, and the lower end of which may be pre-filmed, for transmitting therethrough. The lower end of the sample cell may be formed of a film (e.g., mylar) which can be wrapped tightly around the lower end of the body, and held in place using known techniques. The film is preferably designed with enough strength to hold the sample, while allowing penetration of x-rays, and resultant x-ray fluorescence from/to the x-ray analysis engine. In one embodiment, the sample cup may be a Chemplex sample cup #1850 having the approximate dimension shown in Figs. 4-5; or alternatively an XOS Accu-Cell, as disclosed in commonly-assigned U.S. Patent No. 7,729,471, the entirety of which is hereby incorporated herein by reference. Exemplary sample types include liquids, partial-liquids, granular mixed liquid/solid material (e.g., soil), or a solid (e.g., powder) sample.

[0038] Figs. 6a-b are partial, cross-sectional views of the x-ray engine 100 in accordance with an aspect of the present invention. Sample cell 142 is shown inside of carriage 140 positioning the sample precisely at the focal area 143 created by an excitation x-ray beam 124. Beam 124 can be spatially and/or spectrally focused toward the focal area 143 using x- ray optic 114 which accepts beam 122 from x-ray source / tube 112 (as discussed above).

[0039] Detector 120 is positioned near the focal area to detect fluorescence from the sample. In accordance with the present invention, and with reference to Fig. 6b, a very low angle or glancing angle of incidence (AOI - e.g., 20-25 degrees or less) can be provided to allow detector 120 to be placed very close to the sample (e.g., distance of 4mm, 5mm, 7mm, 10mm). Closeness to the sample allows lower cost detector and also lower cost x-ray excitation techniques. Moreover, this fixed architecture allows detector / sample cell to stay at a very stable distance (+/- 50 um) which is important to calibrate excitation and detection x-ray paths. This fixed architecture also allows for the volume production of internal housings (e.g., 150) thereby lowering part count.

[0040] In another embodiment, a lower incident angle (1-10 degree) can allow an air gap less than 2mm to achieve Na, Mg, Al and Si analysis without vacuum in the excitation path. Selective monochromatic excitation energies (for example the Argon peak in the x-ray spectrum) can be used to correct any variations in the air path. Further, non-point focusing optics can be used, for example line or curved line focusing geometries.

[0041] Fig. 7 shows the external of the XRF analyzer 200 of the present invention having an internal x-ray engine (discussed above), a simple user display (e.g., tablet computer or similar screen) and user access to the sample carriage 140/240 for inserting/removing the sample cell as discussed above.

[0042] With reference to Figs. 8 and 9a-b, shown therein is an alternate embodiment 240 of a sample cell carriage in accordance with the present invention, here a hinged sample cell carriage. In this embodiment, a generally L-shaped bracket comprising a sample cell holding plate 244 and lid 246 are rigidly attached together at about 90 degrees, and together hingedly attached to the housing 240 to carry a sample cell 242 in and out of the focal point (not labeled) of incident x-rays 224. [0043] An x-ray shutter 250 is provided over the x-ray beam aperture, and is mechanically pivoted into an open or closed position depending on the position of pin 248.

[0044] When bracket 244/246 is completely open (Fig. 8), a user can position sample cell 242 into plate 244 in a typical horizontal "table top" position (using features, not shown, which accept and hold sample cell 242). In the fully open or any partially open position (Fig. 9a) x-ray shutter 250 remains closed (because pin 248 has not reached its activating position) thereby blocking any x-rays from entering the housing 240 and beyond.

[0045] When bracket 244/246 is fully closed (Fig. 9b), sample cell 242 is placed (in a vertical position) against the x-ray aperture, and x-ray shutter 250 opens via pushing action of pin 248 thereby allowing x-rays 224 through the aperture to excite sample in sample cell 242. In this position, x-rays are reaching the sample cell and potentially the inside of the housing 240. However, housing 240, plate 244, and/or lid 246 can be designed to shield x-rays from further transmission. Lid 240 can be further protective using "labyrinth joints" along its perimeter to prevent x-ray transmission along its perimeter.

[0046] The automatic sample cell placement/shutter activation features of the present invention allows fewer component parts and more robust "in the field" operation, and can be implemented without a complex interlock scheme to prevent accidental x-ray transmission outside the unit.

[0047] The above features provide a compact, low component count XRF engine of the present invention providing a small, low cost, simple and reliable XRF system suitable for in- the-field applications.

[0048] Exemplary analytes measured in accordance with the present invention include: S, CI, P, K, Ca, V, Mn, Fe, Co, Ni, Cu, Zn, Hg, As, Pb, and/or Se.

[0049] Although preferred embodiments have been depicted and described in detail herein, it will be apparent to those skilled in the relevant art that various modifications, additions, substitutions and the like can be made without departing from the spirit of the invention and these are therefore considered to be within the scope of the invention as defined in the following claims.

Claims

Claims What is claimed is:

1. An x-ray engine apparatus, comprising: a sample cell carriage for inserting and removing a sample cell to and from a measurement focal area of the x-ray engine, wherein adequate x-ray containment surfaces are included along the surfaces and path of the carriage to contain x-rays from emanating during insertion and removal.

2. The apparatus of claim 1, further comprising the sample cell, the sample cell being insertable and removable from the sample cell carriage by a user, during which x-rays remain contained.

3. An x-ray engine apparatus, comprising: a sample cell carriage for inserting and removing a sample cell to and from a measurement focal area of the x-ray engine, wherein an x-ray shutter is automatically engaged by the carriage to contain x-rays from emanating during insertion and removal.

4. The apparatus of claim 1, further comprising the sample cell, the sample cell being insertable and removable from the sample cell carriage by a user, during which x-rays remain contained.

5. The apparatus of claims 1 or 2, wherein incident x-rays are focused to the measurement focal area in the engine at a low angle of incidence (e.g., 20-25 degrees or less) to thereby allow a detector to be located close to the measurement focal area (e.g., 5mm) without substantially blocking the incident x-rays.

6. The apparatus of any of the above claims, in combination with an x-ray analyzer, the x-ray analyzer comprising an x-ray engine including: an x-ray excitation path; and an x-ray detection path; wherein the x-ray excitation and/or the x-ray detection path defines the measurement focal area.

7. The combination of claim 6, wherein the focal area is a focal point.

8. The combination of claim 7, wherein the focal point is defined by focused x- rays to/from at least one focusing optic in the x-ray excitation path and/or the x-ray detection path.

9. The combination of claim 8, wherein the at least one focusing optic is at least one curved diffracting optic or polycapillary optic.

10. The combination of claim 8, wherein the at least one focusing optic is at least one focusing monochromatic optic.

11. The combination of claim 10, wherein the at least one focusing

monochromatic optic is a curved crystal optic or curved multi-layer optic.

12. The combination of claim 7, wherein at least one focusing optic in the x-ray detection path is positioned such that an input focal point thereof is at the x-ray focal point, and corresponds to an output focal point of at least one focusing optic in the x-ray excitation path.

13. The combination of claim 6, wherein the analyzer comprises a monochromatic wavelength-enabled XRF analyzer.

14. The combination of claim 13, wherein the analyzer is an MWDXRF or ME- EDXRF analyzer.

15. The apparatus of any of the above claims, wherein the sample comprises a liquid, partial-liquid, granular mixed liquid/solid material (e.g., soil), or a solid (e.g., powder) sample requiring the measurement of an analyte therein.

16. The apparatus of any of the above claims, wherein an analyte measured is at least one element chosen from the following list: S, CI, P, K, Ca, V, Mn, Fe, Co, Ni, Cu, Zn, Hg, As, Pb, and Se.

17. The apparatus of any of the above claims wherein the sample is a non- homogeneous sample.