There is an emerging need to provide manufactured products of all types in which the levels of toxins is minimized or completely eliminated. This need has a clear underlying medical basis and is accelerated by fear and pending legislation—the results of many recent well-publicized cases of toxins in manufactured products (e.g., lead in toys). The costs of unsafe products go well beyond the health impact to include significant loss of business, permanent damage to brands and corporate image, and increased levels of corporate and personal liability.
In response to these problems, there is a growing trend of increasingly strict environmental and health regulations of consumer products around the world. The list of products regulated is rapidly increasing and the types and permitted levels of toxins are becoming more restrictive. Some industry players are going beyond the regulations for the products they distribute, by mandating even cleaner products in their supply chain. Regulations are effectively aimed at decreasing direct human exposure to toxins by reducing toxins in our environment. Several stricter standards can be traced to European environmental directives that began in the early 1990s, starting with regulations in packaging materials and batteries. In subsequent years, reductions on hazardous substances were introduced by the EU for automobiles (ELV) and two directives related to electronics (Restriction of Hazardous Substances or RoHS and Waste Electrical and Electronic Equipment or WEEE). Pending U.S. Federal legislation lowers allowable lead levels in paint on toys by a factor of six and threatens criminal prosecution for companies that violate with penalties ranging from $10 million to $100 million for a single violation. In addition, nine other known toxins are targeted for restriction, including: mercury, arsenic, cadmium, barium, and chromium.
The spread of such human health and environmental initiatives are having profound global implications on the way products are designed, manufactured, and ultimately discarded or recycled.
Current measurement methods for toxins in manufactured products do not meet the needs of the supply chain, from the factories to the ultimate consumers. Identification and measurement of toxins are needed at each step of the chain, from raw materials, to components, to finished goods. While raw-material measurements are most efficient for factories, distribution channels typically require measurements on the final product. New techniques are urgently needed to accurately, quickly, consistently, and cost-effectively measure toxins at each stage, with minimal interruptions in the flow of manufacturing and distribution of the goods. Because toys and other manufactured products often have small painted features (pigments are often the source of the toxins), it is necessary to measure small areas while differentiating the paint from the base material.
Existing low-cost methods of toxin detection are generally ineffective, e.g., swab tests. Higher-cost methods that provide the requisite accuracy are expensive and time consuming. These sometimes involve: manually scraping samples, digesting them in acids at elevated temperature and pressure, introducing them into a combustion chamber, and analyzing the combustion product. One widely used method today is inductively coupled plasma optical emission spectroscopy (ICP-OES)—a method which is expensive, destructive, and slow. Alternatively, handheld x-ray fluorescence (XRF) guns are rapid and nondestructive, but are only reliable for higher than regulated concentrations, and are averaged across large sample areas, and cannot separately evaluate paint layers.
As discussed further below, the present invention provides a measurement solution having fast, accurate results for toxins in manufactured products, enabled by sophisticated proprietary x-ray optics. Such proprietary optics typically provide 10-1,000× improvements in the ability to focus x-rays; and optic-enabled analyzers are especially suited for these targeted markets—moving measurements from the lab into the factory, field, and clinic.
In x-ray analysis systems, high x-ray beam intensity and small beam spot sizes are important to reduce sample exposure times, increase spatial resolution, and consequently, improve the signal-to-background ratio and overall quality of x-ray analysis measurements. In the past, expensive and powerful x-ray sources, such as rotating anode x-ray tubes or synchrotrons, were the only options available to produce high-intensity x-ray beams, in the laboratory. Recently, the development of x-ray optic devices has made it possible to collect the diverging radiation from an x-ray source by focusing the x-rays. A combination of x-ray focusing optics and small, low-power x-ray sources can produce x-ray beams with intensities comparable to those achieved with more expensive devices. As a result, systems based on a combination of small, inexpensive x-ray sources, excitation optics, and collection optics have greatly expanded the availability and capabilities of x-ray analysis equipment in, for example, small laboratories and in the field, factory, or clinic, etc.
Monochromatization of x-ray beams in the excitation and/or detection paths is also useful to excite and/or detect very precise portions of the x-ray energy spectrum corresponding to various elements of interest (lead, etc.). X-ray monochromatization technology is based on diffraction of x-rays on optical crystals, for example, germanium (Ge) or silicon (Si) crystals. Curved crystals can provide deflection of diverging radiation from an x-ray source onto a target, as well as providing monochromatization of photons reaching the target. Two common types of curved crystals are known as singly-curved crystals and doubly-curved crystals (DCCs). Using what is known in the art as Rowland circle geometry, singly-curved crystals provide focusing in two dimensions, leaving x-ray radiation unfocused in the third or orthogonal plane. Doubly-curved crystals provide focusing of x-rays from the source to a point target in all three dimensions. This three-dimensional focusing is referred to in the art as “point-to-point” focusing.
Commonly-assigned U.S. Pat. Nos. 6,285,506 and 7,035,374 disclose various configurations of curved x-ray optics for x-ray focusing and monochromatization. In general, these patents disclose a flexible layer of crystalline material (e.g., Si) formed into curved optic elements. The monochromating function, and the transmission efficiency of the optic are determined by the crystal structure of the optic.
The ability to focus x-ray radiation to smaller spots with higher intensities, using focusing and monochromating x-ray optics, has enabled reductions in the size and cost of x-ray tubes, and x-ray systems have therefore been proliferating beyond the laboratory to in-situ, field uses. Commonly-assigned U.S. Pat. Nos. 6,934,359 and 7,072,439, incorporated by reference herein in their entirety, disclose monochromatic wavelength dispersive x-ray fluorescence (MWD XRF) techniques and systems, using doubly curved crystal optics in the excitation and/or detection paths. The x-ray optic-enabled systems described in these patents have enjoyed widespread success beyond the laboratory, for measuring sulfur in petroleum fuels in a variety of refinery, terminal, and pipeline environments.
In such systems, precise optic alignment along an axis defined by a source and sample spot may be required, as illustrated in above-incorporated U.S. Pat. No. 7,035,374, which proposes an arrangement of curved, monochromating optics around a central axis operating according to Bragg diffraction conditions. FIG. 1a is a representative isometric view of this x-ray optic arrangement 150 having a curved optic 152, an x-ray source location 154, and an x-ray target location 156. X-ray source location 154 and x-ray target location 156 define a source-to-target transmission axis 162. Optic 152 may include a plurality of individual optic crystals 164, all of which may be arranged symmetrically about axis 162.
FIG. 1b is a cross-sectional view taken along section lines 1b-1b of FIG. 1a, wherein the surface of optic 152, x-ray source location 154, and x-ray target location 156 define one or more Rowland (or focal) circles 160 and 161 of radius R for optic 152. Those skilled in the art will recognize that the number and orientation of the Rowland circles associated with crystal optic 152, or individual crystals 164, will vary with the position of the surface of optic crystal 152, for example, the variation of the toroidal position on optic crystal 152.
The internal atomic diffraction planes of optic crystal 152 also may not be parallel to its surface. For example, as shown in FIG. 1b, the atomic diffraction planes of crystal 152 make an angle γ1 with the surface upon which x-rays are directed, at the point of tangency 158 of the surface and its corresponding optic circle 160 or 161. θB is the Bragg angle for crystal optic 152 which determines its diffractive effect. Each individual optic crystal can in one example be fabricated according to the method disclosed in above-incorporated U.S. Pat. No. 6,285,506, entitled “Curved Optical Device and Method of Fabrication.”
All individual crystals 164 should be aligned to the source-to-target axis 162, for proper Bragg conditions. Improvement in optic alignment, especially for such multiple-crystal optics, therefore remains an important area of interest. Another issue, which particularly affects volume manufacturing, is the need to align disparate components which may be purchased from different vendors. For example, the x-ray tubes, when purchased in quantities from a vendor, may have source x-ray spots which are not consistently centered relative to their own housings. Re-centering these x-ray tube spots is necessary, as an initial step in the alignment process for an entire x-ray source assembly.
Various optic/source combinations have already been proposed to handle thermal stability, beam stability, and alignment issues, such as those disclosed in commonly assigned U.S. Pat. Nos. 7,110,506; 7,209,545; and 7,257,193. Each of these patents is also incorporated herein by reference in its entirety. In particular, U.S. Pat. Nos. 7,209,545 (entitled “X-Ray Source Assembly Having Enhanced Output Stability, and Fluid Stream Analysis Applications Thereof”) and 7,257,193 (entitled “X-Ray Source Assembly Having Enhanced Output Stability Using Tube Power Adjustments and Remote Calibration”) address certain tube/optic alignment problems during source operation with real-time, corrective feedback approaches for alignment between the tube focal spot, optic, and output focal spot. Sensors are used to detect various operating conditions, and mechanical and/or thermal adjustments are made to correct for instabilities, including misalignments. These types of systems are necessary and valuable for certain applications, but can also increase the cost and complexity of fielded systems.
The above-described XRF technology and systems have been useful in single element analyzers for measuring generally homogeneous sample structure (e.g., sulfur in petroleum products). However, the measurement of toxins in manufactured products presents an additional level of challenges. First, an instrument should have the capability to measure more than one element simultaneously or near-simultaneously, from a relatively confined list of about 10 toxic elements, discussed above. Moreover, manufactured products are likely to be heterogeneous in nature, requiring small spot resolution, as well as the ability to detect toxins in one of a number of heterogeneous layers (e.g., the level of lead in a paint layer and a substrate layer beneath the paint).
Improved x-ray analysis method and systems are required, therefore, to address the problems associated with measuring multiple toxins in potentially heterogeneous samples, to enable in-the-factory and/or in-the-field measurement of toxins in manufactured products.