An X-ray Fluorescence Sample Analyzer and Related Method
Field of the Invention
This invention generally relates to X-ray-based analytical instruments and more particularly to X-ray fluorescence analyzers and related methods.
Background of the Invention
X-ray fluorescence analyzers (XRF analyzers) are well-known in the art for determining the elemental composition of a sample. For example, XRF analyzers are used to determine the composition of a test material, such as a metal alloy or a precious metal that contains trace elements. XRF analyzers generally include an X-ray source, which irradiates the sample, and an X-ray detector, which is configured to detect the Xray fluorescence emitted by the sample in response to the rradiation. Some systems also include a microprocessor for controlling the X-ray detector and X-ray source. Each element in the sample emits X-ray fluorescence in energy bands that are characteristic of the element. The detected X-ray fluorescence is analyzed to find the energies or, equivalently, the wavelength of the detected photons, and the qualitative and/or quantitative composition of the sample is determined based on this analysis. However, in the presence of air, such systems cannot accurately detect a broad range of elements in a sample, especially the elements with low atomic numbers. It was discovered that such elements are possible to detect with better precision in a vacuum. In accordance with this discovery, some prior art XRF analyzers employ vacuum chambers, but such chambers leak over time, and as a consequence, the vacuum level gets lower, which requires constant vacuum monitoring by means of pressure and temperature sensors. Because the prior art XRF analyzers typically utilize pressure and temperature sensors for vacuum monitoring, such analyzers are expensive, requiring periodic recalibration, and also not reliable in producing accurate measurement results.
Summary
It is therefore an object of the present invention to provide an XRF sample analyzer and related method that result in such a device that is less expensive than the prior art devices. It is further object of the present invention to provide an XRF sample analyzer and
related method that result in such a device that requires no periodic recalibration. It is yet further object of the present invention to provide an XRF sample analyzer and related method that result in such a device that is characterized by accurate and reliable measurements. The subject invention, in one aspect, results form the partial realization that a cheaper, reliable, accurate, and no recalibration requiring device is effected by replacing the prior art monitoring sensors with the vacuum monitoring conducted by a processing subsystem via analysis of an X-ray fluorescence of gaseous elements present in a vacuum chamber as compared with the predetermined threshold levels. In one embodiment of the present invention, an X-ray fluorescence analyzer includes a vacuum chamber, a window sealed with respect to the vacuum chamber, an x-ray source sealed with respect to the vacuum chamber and disposed to transmit x-rays through the vacuum chamber and the window to a sample. There is a detector subsystem sealed with respect to the vacuum chamber, responsive to x-rays fluoresced by the sample and passing back through the window and the vacuum chamber, and responsive to x-rays fluoresced by any gaseous elements in the vacuum chamber. A processing subsystem responsive to the detector subsystem is also provided and configured to determine which elements are present in the sample based on the x-rays fluoresced by the sample. The processing subsystem is also configured to estimate the amount of at least one gaseous element in the vacuum chamber based on x-rays fluoresced by said gaseous element in the vacuum chamber, and generate an alarm signal when the amount of the at least one gaseous element in the vacuum chamber exceeds a predetermined threshold. In some embodiments, the processing subsystem is configured to generate an alarm signal when the amount of argon in the vacuum chamber exceeds a predetermined threshold. In one version, the XRF analyzer further includes a display. In another example, the processing subsystem is further configured to display an indication of the alarm signal on the display. In one instance, the XRF analyzer further includes a port in the vacuum chamber for evacuating the vacuum chamber. An x-ray fluorescence analysis method is also disclosed. The method includes a step of transmitting x-rays through the vacuum chamber and the window to a sample. It further includes a step of detecting x-rays fluoresced by the sample and passing back through the window and the vacuum chamber. The method further involves detecting xrays fluoresced by any gaseous elements in the vacuum chamber and subsequent step of determining which elements are present in the sample based on the x-rays fluoresced by the sample. It also includes a step of further estimating the amount of at least one gaseous element in the vacuum chamber based on x-rays fluoresced by said gaseous element in the vacuum chamber. The method culminates in a step of generating an alarm signal when the amount of the at least one gaseous element in the vacuum chamber exceeds a predetermined threshold. In one version, the method includes a step of estimating the amount of argon in the vacuum chamber based on x-rays fluoresced by argon in the vacuum chamber with subsequent generating of an alarm signal when the amount of argon in the vacuum chamber exceeds a predetermined threshold. In one example, the method further includes a step of displaying an indication of an alarm signal on a display. In another version, the method further includes a step of evacuating the vacuum chamber if the alarm signal has been generated. And yet in another instance, the method further includes a step of evacuating the vacuum chamber if the alarm signal has been displayed. Figure 1 is a schematic illustration showing an XRF sample analyzer, in accordance with a preferred embodiment of the present invention; Figure 2 is a flow chart of the steps describing how a microprocessor is configured to estimate a vacuum level in a chamber and related method of x-ray analysis; and Figure 3 is a graph showing exemplary fluoresced spectra of Argon used by microprocessor to estimate a vacuum level in a chamber.
Specification
X-ray fluorescence analyzer 10, shown in FIG. 1, in accordance with the preferred embodiment of the present invention, includes vacuum chamber 12, window 24 sealed with respect to vacuum chamber 12, X-ray source 14 sealed with respect to vacuum chamber 12 and disposed to transmit x-rays through vacuum chamber 12 and window 24 to sample 26. Detector subsystem 16 sealed with respect to vacuum chamber 12 is also included; it is responsive to x-rays fluoresced by sample 26 and passing back through window 24 and vacuum chamber 12. Detector subsystem 16 is also responsive to x-rays fluoresced by any gaseous elements in vacuum chamber 12. Processing subsystem 18, which could be a microprocessor, or any other controller with an electronic circuit therein, is responsive to detector subsystem 16 and configured to determine which elements are present in sample 26 based on the x-rays fluoresced by sample 26. Processing subsystem 18 is also connected to memory 22 in which fluoresced spectra are stored. A vacuum is maintained in vacuum chamber 12, FIG. 1, in order to more accurately determine the presence of elements with low atomic numbers. However, because any vacuum chamber leaks over time, there is a need for the constant vacuum monitoring. Prior art XRF analyzers employ expensive temperature and pressure sensors, which are not accurate and require periodic recalibration. The present invention eliminates the need of using such sensors by utilizing the vacuum monitoring carried out by processing subsystem 18 (FIG.1), which is also configured to estimate the amount of at least one gaseous element in vacuum chamber 12 based on x-rays fluoresced by said gaseous element in vacuum chamber 12 and generate an alarm signal when the amount of the at least one gaseous element in vacuum chamber 12 exceeds a predetermined threshold, which is stored in memory 22 connected to processing subsystem 18, FIG. 1. In some embodiments, processing subsystem 18, FIG.1, is configured to estimate the amount of Argon in vacuum chamber 12 based on x-rays fluoresced by Argon in vacuum chamber 12. When the amount of Argon in vacuum chamber 12, FIG.1, exceeds a predetermined threshold, processing subsystem 18, FIG. 1, will generate an alarm signal. This is illustrated in FIG. 3, where a fluoresced spectrum 1 of Argon intensity, being above a predetermined threshold of 40 counts per second (the dashed line on a graph, FIG. 3), triggers the alarm signal; whereas, fluoresced spectrum 2 of Argon intensity, being below the predetermined threshold of 40 counts per second (the dashed line on a graph, FIG. 3), triggers no alarm signal. In some embodiments, processing subsystem 18 can be connected to input/output display 20, shown in FIG. 1. In another version, processing subsystem can be configured to display an indication of an alarm signal on the display (e.g., input/output display 20, FIG. 1). In one example, XRF analyzer 10, FIG. 1, can also include port 28 in vacuum chamber 12 for evacuating vacuum chamber 12. An XRF analysis method is also disclosed. Figure 2 shows a flow chart illustrating an XRF analysis method, including how processing subsystem of an XRF sample analyzer is configured to determine a vacuum level in a vacuum chamber based on Argon intensity. A method includes the steps of transmitting x-rays through the vacuum chamber and the window to a sample, detecting x-rays fluoresced by the sample and passing back through the window and the vacuum chamber. The method further includes detecting x-rays fluoresced by any gaseous elements (e.g., Argon, Oxygen, Nitrogen, or Hellium) in the vacuum chamber and subsequently determining which elements are present in the sample based on the x-rays fluoresced by the sample. The XRF analysis method further includes the steps of estimating the amount of at least one gaseous element in the vacuum chamber based on x-rays fluoresced by said gaseous element in the vacuum chamber and generating an alarm signal when the amount of the at least one gaseous element in the vacuum chamber exceeds a predetermined threshold. If, for example, Argon amount is greater than a predetermined threshold (spectrum 1, FIG. 3), then a processing subsystem (e.g., microprocessor) will generate an alarm signal, FIG. 2. For example, the alarm signal can be an audible alarm, or can be displayed on a display. Upon generating of such an audible alarm signal or displaying an alarm signal on a display, an operator of an XRF analyzer will connect a vacuum line (port 28, FIG. 1) to a vacuum pump for evacuating a chamber (see flow chart in FIG.2). If the amount of Argon is not greater than a predetermined threshold (e.g., spectrum 2, FIG. 3), then a microprocessor will not generate the alarm signal, but will continue estimating the amount of Argon in a vacuum chamber (see FIG. 2). In sum, the described above embodiment and related method of the present invention result in such an XRF sample analyzer that is more accurate, less expensive and requiring no periodic recalibration as compared with the prior art devices.
Claims
1. An x-ray fluorescence analyzer comprising:
a vacuum chamber;
a window sealed with respect to the vacuum chamber;
an x-ray source sealed with respect to the vacuum chamber disposed to transmit x-rays through the vacuum chamber and the window to a sample;
a detector subsystem sealed with respect to the vacuum chamber, responsive to x-rays fluoresced by the sample and passing back through the window and the vacuum chamber, and responsive to x-rays fluoresced by any gaseous elements in the vacuum chamber; and a processing subsystem responsive to the detector subsystem and
configured to:
determine which elements are present in the sample based on the x-rays fluoresced by the sample, estimate the amount of at least one gaseous element in the vacuum chamber based on x-rays fluoresced by said gaseous element in the vacuum chamber, and generate an alarm signal when the amount of the at least one gaseous element in the vacuum chamber exceeds a predetermined threshold.
2. The analyzer of claim 1 in which said at least one gaseous element is argon.
3. The analyzer of claim 1 further including a display.
4. The analyzer of claim 3 in which the processor is further configured to display an indication of said alarm signal on the display.
5. The analyzer of claim 1 further including a port in said vacuum chamber for evacuating the vacuum chamber.
6. An x-ray fluorescence analysis method comprising: transmitting x-rays through the vacuum chamber and the window to a sample;
detecting x-rays fluoresced by the sample and passing back through the window and the vacuum chamber; detecting x-rays fluoresced by any gaseous elements in the vacuum chamber; determining which elements are present in the sample based on the x-rays
fluoresced by the sample; estimating the amount of at least one gaseous element in the vacuum chamber based on x-rays fluoresced by said gaseous element in the vacuum chamber; and generating an alarm signal when the amount of the at least one gaseous element in
the vacuum chamber exceeds a predetermined threshold.
7. A method of claim 6 wherein said at least one gaseous element is argon.
8. A method of claim 6 further comprising displaying an indication of said alarm signal on a display.
9. A method of claim 6 further comprising evacuating said vacuum chamber if said alarm signal has been generated.
10. A method of claim 8 further comprising evacuating said vacuum chamber if said alarm signal has been displayed.
Abstract
Device, such as an X-ray fluorescence sample analyzer (XRF analyzer), and method associated with such a device are provided. The X-ray fluorescence analyzer includes a vacuum chamber, a window sealed with respect to the vacuum chamber, an x-ray source sealed with respect to the vacuum chamber and disposed to transmit x-rays through the vacuum chamber and the window to a sample. There is a detector subsystem sealed with respect to the vacuum chamber, responsive to x-rays fluoresced by the sample and passing back through the window and the vacuum chamber, and responsive to x-rays fluoresced by any gaseous elements in the vacuum chamber. A processing subsystem responsive to the detector subsystem is also provided and configured to determine which elements are present in the sample based on the x-rays fluoresced by the sample. The processing subsystem is also configured to estimate the amount of at least one gaseous element in the vacuum chamber based on xrays fluoresced by said gaseous element in the vacuum chamber, and generate an alarm signal when the amount of the at least one gaseous element in the vacuum chamber
exceeds a predetermined threshold.