More particularly, the invention relates to apparatus and methods for supplying power to electronic devices. Even more particularly, the invention relates to a power supply for an x-ray device, including a portable x-ray device and a method for using the same.

BACKGROUND OF THE INVENTION There has been significant interest in apparatus and methods for identifying and verifying various articles or products such as explosives, ammunition, paint, petroleum products, and documents. Known methods used to identify and verify generally involve adding and detecting materials like code-bearing microparticles, bulk chemical substances, and radioactive substances. Other methods used for identifying and verifying articles include those described in U. S. Patent Nos. 6,030, 657,6, 024,200, 6,007, 744, 6,005, 915,5, 849,590, 5,760, 394,5, 677,187, 5,474, 937,5, 301,044, 5,208, 630,5, 057, 268, 4,862, 143,4, 390,452, 4,363, 965, and 4,045, 676, as well as European Patent Application Nos. 0911626 and 0911627, the disclosures of which are incorporated herein by reference.

It is also known to apply materials to articles in order to track, for example, point of origin, authenticity, and their distribution. In one method, inks that are transparent in visible light are sometimes applied to materials and the presence (or absence) of the ink is revealed by ultraviolet or infrared fluorescence. Other methods include implanting microscopic additives that can be detected optically. However, detecting these materials is primarily based on optical or photometric measurements.

Numerous devices are known for identifying and verifying articles containing such materials (called taggants) by x-ray fluorescence (XRF). See, for example, U. S. Patent Nos. 5,461, 654,6, 130,931, 6,041, 095,6, 075,839, 6,097, 785, and 6,111, 929, the disclosures of which are incorporated herein by reference. Unfortunately, many of the known apparatus for are unsatisfactory for several reasons. First, they are often difficult and time-consuming to use. In many instances, a sample of the article must be sent to an

off-site laboratory for analysis. In other instances, the apparatus are often expensive, large, and difficult to operate. For example, the known apparatus and methods for identification and verification are also unsatisfactory because the devices employed are <BR> <BR> usually not portable. Even when portable, they are only semi-portable, e. g. , the portability is limited because of the connection between the power supply and the rest of the operating device.

Second, the known devices are unsatisfactory because of the operating frequency.

Many of the known devices are often limited in the frequency range in which they can operate. Most of the known devices are limited to working frequencies from 30-50 KHz range. In many instances, however, higher operating frequencies like those in 100 KHz, and particularly the 1-3 MHz range, are desirable. Such higher frequencies are often unattainable because of cost and size considerations.

SUMMARY OF THE INVENTION The invention provides apparatus and methods for supplying power to electronic devices such as portable electronic devices for x-ray fluorescence analysis. The apparatus is able to operate at the higher frequencies that can be desirable for detecting and analyzing certain taggants, without the attendant cost and size limitations, by using small, low voltage components. Working at such higher frequencies while using smaller components allows for faster switching times and higher efficiency, as well as smaller sizes and decreased costs.

BRIEF DESCRIPTION OF THE DRAWINGS Figures 1,2a, 2b, 3,4a, 4b, 5-11,12a, 12b, 12c, 12d, and 13-15 are views of one aspect of apparatus and methods according to the invention, in which: Figure 1 generally depicts the operation of XRF ; Figure 2a and 2b illustrate the operation of XRF at the molecular level; Figure 3 shows an exemplary x-ray spectrum, e. g. , for paper; Figure 4a and 4b depict two aspects of the of the XRF apparatus of the invention; Figure 5 illustrates exemplary energy levels of x-rays in an x-ray spectrum; Figure 6 shows another aspect of the XRF apparatus of the invention; and

Figures 7 illustrates an x-ray source in one aspect of the invention;.

Figure 8 depicts various components in the power supply in one aspect of the invention ; Figure 9 shows the voltage connection means in one aspect of the invention; Figure 10 depicts a lightpipe in one aspect of the invention; Figure 11 depicts a filament system in one aspect of the invention; Figures 12a, 12b, 12c, and 12d illustrate the various components in a high voltage system in one aspect of the invention; Figures 13 and 14 illustrate connection of the power supply to the x-ray source in one aspect of the invention; and Figure 15 schematically illustrate connection of the power supply to the x-ray source in one aspect of the invention.

Figures 1,2a, 2b, 3,4a, 4b, 5-11,12a, 12b, 12c, 12d, and 13-15 presented in conjunction with this description are views of only particular-rather than complete- portions of apparatus and methods according to the invention. Together with the following description, the Figures demonstrate and explain the principles of the invention.

DETAILED DESCRIPTION OF THE INVENTION The following description provides specific details in order to provide a thorough understanding of the invention. The skilled artisan would understand, however, that the invention can be practiced without employing these specific details. Indeed, the invention can be practiced by modifying the illustrated apparatus and method and can be used in conjunction with apparatus and techniques conventionally used in the industry. For example, the invention is described with respect to using the power supply device (and method) in an XRF detecting apparatus. The invention described below, however, could be easily modified to power devices other than XRF apparatus, such as portable devices, benchtop systems, and x-ray devices. Indeed, the power supply device and method of the invention could be used to supply power to any known device that requires power, whether portable or not.

In one aspect, the invention uses x-ray fluorescence analysis to detect at least one taggant intrinsically or extrinsically present in the material of a product or article. With x-

ray fluorescence (XRF) analysis, x-rays produced from electron shifts in the inner shell (s) of atoms of the taggants and, therefore, are not affected by the fonn (chemical bonding) of the article being analyzed. The x-rays emitted from each element bear a specific and unique spectral signature, allowing one to determine whether that specific taggant is present in the product or article.

Figures 1,2a, and 2b represent how it is believed XRF generally operates. In Figure 1, primary gamma rays or x-rays 40 are irradiated on a sample of a target material 46 of article 42. Secondary x-rays 44 are emitted from that sample of target material 46.

In Figures 2a and 2b, atom 48 of a taggant located within target material 46 has nucleus 50 surrounded by electrons 52 at discrete distances from nucleus 50 (called electron shells). Each electron shell has a binding energy level equal to the amount of energy required to remove that electron from its corresponding shell. The innermost shell is the K shell, and has the highest binding energy level associated with it. Electron 54 is located within K shell 56.

Primary x-ray or gamma ray photon 40 impacting atom 48 has a given energy. If that energy is greater than the binding energy level of K shell 56, the energy of x-ray photon 40 is absorbed by atom 48, and one of the electrons in K shell 56 (i. e. , electron 54) is ejected. With a vacancy now in K shell 56 left by electron 54, atom 48 is energetic and unstable. To become more stable, that vacancy in K shell 56 can be-and usually is- filled by an electron located in a shell with a lower binding energy level, such as L-shell electron 58 in L shell 60. As L-shell electron 58 fills the vacancy in K shell 56, atom 48 emits a secondary x-ray photon 44. The energy levels (or corresponding wavelengths) of such secondary x-ray photons are uniquely characteristic to each taggant, allowing the presence or absence of any specific taggant to be determined.

As shown in Figure 3, the x-rays which are detected have various energies, e. g., there is a broad band of scattered x-rays with energies less than and greater than those of the exciting atom. Figure 3 illustrates this spectrum for paper as the target material.

Within this broad band, there are peaks due to the excitation of the taggant (s) in the sample. The ratio of the intensity of the radiation in any peak to the intensity of the background at the same energy (known as the peak-to-background ratio) is a measure of

the concentration of the element which has characteristic X-rays at the energy of that peak, e. g. , the thetaggant.

In one aspect of the detection method of the invention, at least one target material believing to contain known concentrations of the taggant (s) of interest is selected. The XRF analysis is performed on that target material (or a sample thereof) using a detection device or apparatus containing an x-ray radiation source ("source"), x-ray radiation detector ("detector"), support means, analyzer means, and calibration means.

One aspect of the detection device of the invention is illustrated in Figure 4a. In this Figure, the detection apparatus 25 has an ordinary x-ray fluorescence spectrometer capable of detecting elements present in a coating, package or material. X-rays 29 from a source (e. g. , either x-ray tube or radioactive isotope) 20 impinge on a sample 11 which absorbs the radiation and emits x-rays 31 to an x-ray detector 21 and analyzer 23 capable of energy or wavelength discrimination. This is accomplished by using a commercially available x-ray spectrometer such as an Edax DX-95 or a MAP-4 portable analyzer, commercially available from Edax Inc., Mahwah, New Jersey. Part of analyzer 23 includes a computerized system 27.

Another aspect of the detection apparatus of the invention is illustrated in Figure 4b. In this Figure, the detection apparatus 25 has an instrument housing 15 which <BR> <BR> contains the various components. Gamma rays or x-rays 30 from a source (e. g. , either x- ray tube or radioactive isotope) 20 are optionally focused by aperture 10 to impinge on a sample 11. Sample 11 contains the at least one taggant which absorbs the radiation and emits x-rays 31 to an x-ray detector 21. Optionally, analyzing means can be incorporated within housing 15.

The invention, however, is not limited to the detection apparatus depicted in Figures 4a and 4b. Any suitable source, or plurality of sources, known in the art can be used as the source in the detection device of the present. See, for example, U. S. Patent Nos. 4,862, 143,4, 045,676, and 6,005, 915, the disclosures of which are incorporated herein by reference. During the XRF detection process, the source bombards the taggant with a high energy beam. The beam may be an electron beam or electromagnetic radiation such as X-rays or gamma rays. The source, therefore, may be any material emitting such high energy beams. Typically, these have been x-ray emitting devices such

as x-ray tubes or radioactive sources. The x-ray source is powered by any suitable power supply, as described below.

To target, the beam can be focused and directed properly by any suitable means such as an orifice or an aperture. The configuration (size, length, diameter...) of the beam should be controlled, as known in the art, to obtain the desired XRF detection. The power (or energy level) of the source should also be controlled, as known in the art, to obtain the desired XRF detection.

The source (s) can be shielded and emit radiation in a space limited by the shape of the shield. Thus, the presence, configuration, and the material used for shielding the source should be controlled for consistent XRF detection. Any suitable material and configuration for that shield known in the art can be employed in the invention.

Preferably, any high-density materials used as the material for the shield, e. g, tungsten or brass.

Any suitable detector, or plurality of detectors, known in the art can be used as the detector in the detection device of the invention. See, for example, U. S. Patent Nos.

4,862, 143,4, 045,676, and 6,005, 915, the disclosures of which are incorporated herein by reference. Any type of material capable of detecting the photons omitted by the taggant may be used. Silicon and CZT (cadmium-zinc-telluride) detectors have been conventionally used, but others such as proportional counters, germanium detectors, or mercuric iodide crystals can be used.

Several aspects of the detector should be controlled to obtain the desired XRF detection. First, the geometry between the detector and the target material should be controlled. The XRF detection also depend on the presence, configuration, and material-such as tungsten and beryllium-used as a window to allow x-rays photons to strike the detector. The age of the detector, voltage, humidity, variations in exposure, and temperature can also impact the XRF detection and, therefore, these conditions should be controlled.

The analyzer means sorts the radiation detected by the detector into one or more energy bands and measures its intensity. Thus, any analyzer means performing this function could be used in the invention. The analyzer means can be a multi-channel analyzer for measurements of the detected radiation in the characteristic band and any

other bands necessary to compute the value of the characteristic radiation as distinct from the scattered or background radiation. See, for example, U. S. Patent Nos. 4,862, 143, 4,045, 676, and 6,005, 915, the disclosures of which are incorporated herein by reference.

The XRF also depends on the resolution of the x-rays. Background and other <BR> <BR> noise must be filtered from the x-rays for proper measurement, e. g. , the signals must be separated into the proper number of channels and excess noise removed. The resolution can be improved by cooling the detector using a thermoelectric cooler-such as a nitrogen or a peltier cooler-and/or by filtering. Another way to improve this resolution is to use pre-amplifiers.

The support means supports the source and detector in predetermined positions relatively to a sample of the target material to be irradiated. Thus, any support means performing this function could be used in the invention. In one example, the support means comprises two housings, where the source and detector are mounted in a first housing which is connected by a flexible cable to a second housing in which the analyzer means is positioned as illustrated in Figure 4a. If desired, the first housing may then be adapted to be hand-held. In another example, the source and detector as well as the other components of the detection device are mounted in a single housing as illustrated in Figure 4b.

The calibration means are used to calibrate the detection apparatus, thus insuring accuracy of the XRF analysis. In this calibration, the various parameters that could be modified and effect the measurement are isolated and calibrated. For example, the geometrical conditions or arrangements can be isolated and calibrated. In another example, the material matrix are isolated and calibrated. Preferably, internal (in situ) calibration during detection is employed as the calibration means in the invention.

Components, such as tungsten shielding, are already present to internally calibrate during the XRF analysis. Other methods, such as fluorescence peak or Compton backscattering, could be used for internal calibration in the invention.

Analyzer means, which includes a computerized system 27, is coupled to, receives, and processes the output signals produced by detector 21. The energy range of interest, which includes the energy levels of the secondary x-ray photons 44 emitted by the taggant (s), is divided into several energy subranges. Computerized system 27

maintains counts of the number of X-ray photons detected within each subrange using specific software programs, such as those to analyze the detection and x-ray interaction and to analyze backscatter data. After the desired exposure time, computerized system 27 with display menus stops receiving and processing output signals and produces a graph of the counts associated with each subrange.

Figure 5 is a representative graph of the counts associated with each subrange.

This graph is essentially a histogram representing the frequency distribution of the energy levels E1, E2, and E3 of the detected x-ray photons. Peaks in the frequency distribution (i. e. , relatively high numbers of counts) occur at energy levels of scattered primary x-ray photons as well as the secondary x-ray photons from the taggant (s). A primary x-ray photon incident upon a target material may be absorbed or scattered. The desired secondary x-ray photons are emitted only when the primary x-ray photons are absorbed.

The scattered primary x-ray photons reaching the detector of the system create an unwanted background intensity level. Accordingly, the sensitivity of XRF analysis is dependent on the background intensity level, and the sensitivity of XRF detection may be improved by reducing the amount of scattered primary x-ray photons reaching the detector. The peak occurring at energy levels of scattered primary x-ray photons is basically ignored, while the other peaks-those occurring at El, E2, and E3-are used to identify the at least one taggant present in the target material.

Besides the parameters described above, at least two other parameters must be controlled during the process of XRF detection. First, the media (such as air) through which the gamma rays (and x-rays) must travel also impacts the XRF. Therefore, the different types of media must be considered when performing the XRF analysis. Second, the methods used to interpret and analyze the x-rays depend, in large part, on the algorithms and software used. Thus, methods must be adopted to employ software and algorithms that will consistently perform the XRF detection.

These two parameters, plus those described above, must be carefully accounted for and controlled to obtain accurate measurements. In one aspect of the intention, these parameters could be varied and controlled to another provide a distinct code. For example, using a specific source and a specific detector with a specific measuring

geometry and a specific algorithm could provide one distinct code. Changing the source, detector, geometry, or algorithm could provide a whole new set of distinct codes.

Figure 6 illustrates a preferred apparatus and detection method according to the invention. In this Figure, detection apparatus 25 is capable of detecting at least one taggant present in target material 10. Detection apparatus 25 is a portable device that is small enough to be hand-held. Detection apparatus 25 contains all the components discussed above (i. e. , source, detector, analyzer means, and calibration means) in a single housing, thus allowing the portability and smaller size.

The x-ray source of the invention can be any known source known in the art. See, for example, U. S. Patent No. 6,178, 226, the disclosure of which is incorporated by reference. In one aspect of the invention, the x-ray source is an x-ray tube 20 as depicted in Figure 7. hi Figure 7, a x-ray tube 20 contains filament 3, which is also connected to cathode 2. A control grid 6 is separated from cathode 2 by a distance ranging from about 0.040 inches to about 0.080 inches. An anode 4 is separated by about 0.05 inches from control grid 6. The power from the power supply means is fed to both the cathode 2 and the control grid 6 to power the x-ray tube as described in more detail below.

The x-ray tube is powered by any suitable power supply means known in the art.

A suitable power supply means in the invention is one supplying the needed power, given the size, cost, portability, and safety requirements for the XRF device. There are numerous power supply devices known in the art that can be employed in the invention.

See, for example, U. S. Patent Nos. 6,130, 931,6, 097, 785, and 6,111, 929, the disclosures of which are incorporated herein by reference. While they can be employed in the invention, they are not preferable since such power supplies are connected to the x-ray source using a power cable. Often, this power cable operates at a high voltage, causing problems with other electronic components in the XRF device even when the power cable is insulated.

In one aspect of the invention, the power supply means of the invention connects to the x-ray tube without a power cable. By not using a power cable, the size and cost of the XRF device is decreased. As well, without the need for a power cable, the XRF device becomes more portable and more stable. In a preferred aspect of the invention, the

x-ray tube is directly connected to the power supply as described below and as depicted in Figures 13-14 and schematically illustrated in Figure 15.

As depicted in Figure 8, the power supply means 102 for the XRF tube 20 of the invention contains several components: a control mechanism (or means) and a dual power supply mechanism (or means). Briefly, the dual power supply means provides the necessary power (voltage) level for the x-ray tube. The control mechanism is employed to control the voltage being provided to the x-ray tube.

Any suitable control mechanism that can regulate the voltages needed to operate the x-ray tube can be employed in the invention. In aspect of the invention, the control mechanism is a light control means. The light control means uses a combination of a light emitting, means connected to a light conveying means, which is in turn connected to control means for the control grid voltage. Any suitable means which emits light as known in the art can be employed as the light emitting means. In a preferable aspect of the invention, the light emitting means is a light emitting diode (LED) such as an infrared emitting diode (IED) 104 depicted in Figure 10.

The light from the light emitting means is then conveyed through the light conveying means to the control grid voltage control means. Any suitable light conveyance means known in the art can be employed in the invention. Preferably, a lightpipe 106 depicted in Figure 10 configured to match light emanating from the light emitting means is employed in the invention.

The light exiting from the light conveying means then enters the control grid voltage control means. The control grid voltage control means regulates the operation of the control grid. In other words, the control grid voltage control means is employed to turn the control grid voltage on and off. Any suitable control means known in the art can be employed in the invention. See, for example, U. S. Patent No. 6,178, 226. In one aspect of the invention, such control grid voltage control means can be connected to and/or combined with other control apparatus in the detection apparatus 25 of the invention, such as with the control means for the detector. In one aspect of the invention, the control grid voltage control means comprises a photodiode 108 as depicted in Figure 10. When light strikes the photodiode, the photodiode is switched on, thereby allowing the control grid voltage to flow as described below.

The dual power supply mechanism of the invention provides the necessary power to the x-ray tube 20 while simultaneously being configured for the desired size, cost, and portability requirements. Any known apparatus or device serving these functions can be employed in the invention. Preferably, the apparatus described below is employed in the invention as the dual power supply mechanism.

The dual power supply mechanism of the invention comprises two systems: the high voltage system (HVS) and the filament system (FS). The high voltage system converts a steady-state, low voltage input from a voltage source 122, such as a battery, to a high voltage/low current output. The high voltage output is then used to power the cathode 2 and control grid 6 of the x-ray tube 20. The filament system serves a dual function. Part of the power supplied by the filament system is used to heat the filament 3 in the x-ray tube 20 as known in the art. As well, part of the power from the filament system is used to provide a control grid voltage.

As illustrated in Figure 12, the high voltage system (HVS) 120 comprises numerous components that cooperate to obtain the desired function of increasing the low voltage into a high voltage. A low voltage source 122 (e. g. , battery) is connected to one end of the HVS. The low voltage source provides a voltage ranging from about 12 volts to about 5 volts to the HVS. The low voltage source can be a part of the HVS, or can be separate from the HVS.

In one aspect of the invention, the low voltage source can be external to the HVS, including external to the sheath (described below) surrounding the power supply device.

In this aspect of the invention, the voltage from a removable low voltage source can be provided to the HVS using voltage connection means that is permanently connected to the HVS. The voltage connection means can be any known in the art, including connector 124 as depicted in Figure 9.

Connected to the low voltage source is means for maintaining a steady-state, constant voltage depending on the voltage of the voltage source. For example, if the battery provides voltage of up to about 12 volts, the maintaining means maintains a constant output voltage ranging from about 1 to about 5 volts. Any such maintaining means known in the art performing such a function can be employed in the invention. In

one aspect of the invention, the maintaining means employed is a DC/DC converter 126 such as LTC1624, as depicted in Figure 9.

Connected to the converting means is converting means for changing the DC voltage to an AC voltage. The converting means converts the incoming DC voltage ranging from about 1 to about 5 volts to an AC voltage ranging from about 1 to about 5 volts. Any converting means known in the art that can perform such a function can be employed in the invention. In one aspect of the invention, the converting means is a generator 128, as depicted in Figure 9.

The voltage exiting from the converting means is then induced by any suitable induction means known in the art, such as a transformer, into the next element of the HVS. The induction means modifies the voltage exiting the generator, modifying or transforming the 1-5 AC voltage to a voltage of about 0.5 to 2.5 volts. Any suitable induction means known in the art obtaining this purpose can be employed in the invention. Preferably, a low voltage host transformer, such as a toroid 130 (see Figure 12), is employed in the invention as the induction means.

Unlike the other components of the HVS, this high voltage transformer is a low voltage component, not a high voltage component. High voltage components-such as this high voltage transformer-are larger and more expensive than low voltage components. The HVS purposefully includes, to the extent possible, low voltage components instead of the high voltage components traditionally used to supply high voltage power. Using less expensive components instead of traditional high voltage components yields the ability to use smaller size components that can be located closer together because of the low electric field strength of the low voltage components.

As depicted in Figure 12, the induction means (toroid 130) is electrically connected to one end of a high voltage drive. The HVS comprises a single turn loop of a high voltage wire. In one aspect of the invention, the toroid 130 is wrapped around the end of the high voltage wire, thus inducing a low voltage into that end of the high voltage wire around which it is wrapped. Using a single turn loop of the high voltage wire, the high voltage drive has a low output resistance. As well, the single turn loop (as described below) provides a base voltage to the multiplying means throughout the HVS.

The HVS also contains means for multiplying the voltage using a plurality of low voltage components. Any means for multiplying the low input voltage into a high output while fulfilling the necessary size and cost requirements, can be employed in the invention. In one aspect of the invention, as depicted in Figure 12, at least one multiplier stage 140 (arranged in series) are employed in the invention as the voltage multiplying means. Each multiplier stage transforms a low input voltage to a higher output voltage.

The multiplier stage is able to increase the voltage depending generally on the load current, components value, work frequency, and number of multiplier modules. The increase in voltage can vary from one stage to the next; allowing the increase to be the same or different for each stage. The number of multiplier stages in the HVS depends on the desired voltage increase for the HVS, and the size (and cost) limitations. In one aspect of the invention, the number of multiplier stages can be 1 or more. Preferably, 7 multiplier stages are provided in the HVS.

Each multiplier stage optionally contains at least one transformer module 144.

Preferably, each multiplier stage contains one transformer module. The number of transformer coil turns within each multiplier stage depends on the desired AC voltage to be supplied to the voltage doubler (s). In one aspect of the invention, a single transformer module is provided in each multiplier stage. Although not preferable, it is possible to configure the entire HVS with any number of multiplier modules yet with a single transformer module, as opposed to any number of multiplier modules coupled with a single transformer module within a given multiplier stage. The number of transformer modules can vary from any given multiplier stage to another.

Each multiplier stage comprises at least one multiplier module. The number of multiplier modules 142 depends on the desired voltage increase, the size and cost restrictions, and desired output current. In one aspect of the invention, the number of multiplier modules can be 1 or more. Preferably, the number of multiplier modules is 4 within any given multiplier stage. The number of multiplier modules can vary from any given multiplier stage to another.

In one aspect of the invention, four multiplier modules are employed with a single transformer module within a single multiplier stage. The configuration-e. g. , sequence- of the multiplier modules and the transformer module depends on size and space

considerations, and the desired output current. In one aspect of the invention, two sets of <BR> <BR> two multiplier modules sandwiches the transformer module, e. g. , sequentially a multiplier module, multiplier module, transformer module, multiplier module, and multiplier module.

Each multiplier module 142 contains at least one voltage doubler 146. In one aspect of the invention, the voltage doubler is a rectifier 148 coupled with a capacitor 150.

In one aspect of the invention, the multiplier module contains a plurality of voltage doublers in series. The number of voltage doublers within any given multiplier module depends on the size of the multiplier module, the desired voltage increase across the multiplier module, and internal resistance. In one aspect of the invention, the number of voltage doublers can be one or more. In one aspect of the invention, 12 to 48 voltage doublers are included within any given multiplier module. Preferably, 24 voltage doublers are included within any given multiplier module. If desired, the number of voltage doublers from one multiplier module to the next can be the same or different.

Each multiplier module contains the smallest amount of circuitry-e. g. , rectifiers and capacitors-needed to increase the voltage by the desired amount. If desired, additional circuitry can be added to any multiplier module as needed. In each multiplier module, the voltage is fed to a series of rectifiers. Each rectifier-as part of the voltage doubler-is able to increase the voltage by an amount ranging form about 50 to about 200 volts. In one aspect of the invention, each rectifier is configure to increase the voltage by about 100 volts. The number of voltage doublers can vary from any given multiplier module to another.

Each transformer module 144 transforms the voltage provided by the single turn loop and feeds it to the capacitors (or the equivalent) of the voltage doublers as a base voltage. The transformer module accomplishes this function by any suitable means known in the art, such as a transformer. In one aspect of the invention, the transformer module modifies the voltage in the single turn loop (1-5 volts) to a base voltage ranging from about 20 to about 200 volts. Any suitable transformer known in the art obtaining this purpose can be employed in the invention. Preferably, a low voltage transformer, such as a low voltage toroid 152 is employed in the invention as the transformer module.

Thus, the voltage increase within any given multiplier module depends the number (and type) of voltage doublers used within that module. The voltage increase for any given multiplier module can be the same or different from any other multiplier module.

In one aspect of the invention, the increase in voltage for a multiplier can range from about 1 volt to about 3000 volts. Preferably, the voltage increase within a single multiplier module is about 2500 volts.

In turn, the voltage increase within any given multiplier stage depends on the number (and type) of multiplier modules within that multiplier stage. The voltage increase for any given stage can be the same or different from any other stage. In one aspect of the invention, the increase in voltage for any individual stage can range from about 1 volt to about 10,000 volts. Preferably, the voltage increase within a single stage is about 8, 000 volts.

Likewise, the voltage increase for the HVS depends on the number (and type) of multiplier stages. The voltage increase any given HVS can be the same or different from any other HVS. hi one aspect of the invention, the increase in voltage for any given HVS can range from about 1 volt to about 70,000 volts. Preferably, the voltage increase within a HVS is about 50,000 volts.

Thus, the increase in the voltage for the HVS depends, therefore, on the number (and type) of multiplies stages, the number (and type) of multiplier modules within any given multiplier stage, the number (and type) of voltage doublers.

The second major component of the dual power supply mechanism is the filament system (FS) 154. As noted above, the filament system serves a dual function. Part of the power supplied by the filament system is used to heat the filament in the x-ray tube described above. As well, part of the power from the filament system is used to provide the control grid voltage as described below. As illustrated in Figure 11, the FS comprises numerous components to obtain the desired function. In the FS, a voltage source (such a battery) 156 is provided for a base DC voltage. Like the HVS, connected to the voltage source is means for maintaining a constant voltage depending on the voltage of the voltage source. For example, if the battery provides voltage of 12 volts, the maintaining means maintains a constant output voltage ranging from about 1 to about 5 volts. Any maintaining means known in the art that can perform such a function can be employed in

the invention. In one aspect of the invention, the maintaining means employed is a DC/DC converter 158 such as LTC 1624.

Connected to the maintaining means is converting means for changing the DC voltage to an AC voltage. The converting means converts the incoming DC voltage ranging from about 1 to about 5 volts to an AC voltage ranging from about 1 to about 5 volts. Any converting means known in the art that can perform such a function can be employed in the invention. In one aspect of the invention, the converting means employed is a generator 160.

The voltage from the generator is then induced by any suitable induction means known in the art, such as a transformer, to the next element of the FS, the filament drive.

The induction means modifies the voltage exiting the converting means, transforming the 1-5 AC voltage to a voltage ranging from about 0.25 to about 1.25 volts. Any suitable induction means known in the art accomplishing this purpose can be employed in the invention. Preferably, a transformer, such as a toroid 162, is employed in the invention as the induction means.

The filament drive comprises a single turn loop of a high voltage wire 164. The single turn loop transmits the voltage from a first location (such as a first end) of the loop 166 to a second location (such as a second end) of the loop 168. At the second location of the loop, the voltage is then induced by any suitable induction means known in the art, such as a transformer, to the x-ray tube 20. Any suitable induction means known in the art accomplishing this purpose, such as a transformer, can be employed in the invention.

Preferably, a host transformer such as a toroid 170 is employed in the invention as the induction means.

The induction means splits the voltage in two. A first portion of the voltage is used to heat the filament. As the voltage used to heat the filament ranges from about 1 to about 5 volts, the induction means need only induce the same amount of voltage from the FS to the filament. Any induction means known in the art that accomplishes this function can be employed in the invention. In one aspect of the invention, a toroid 172 containing a single turn of wire is employed at this induction means.

The second portion of the voltage is used to supply the control grid voltage. The voltage used for the control grid voltage needs to be increased from the FS. In one aspect

of the invention, the induction means needs to increase amount of voltage from the FS by about 400%. Any induction means known in the art accomplishing this function can be employed in the invention. In one aspect of the invention, a toroid 178 containing about four turns of wire is employed at this induction means.

As seen in Figure 11, the single turn loop of the FS is electrically connected to the middle of the HVS to reduce twice voltage applied between one turn loop and output of HVS. The single turn loop of the HVS need not be so connected because it should remain at a half of HVS voltage (the base voltage) throughout its length.

The current of the output potential of the HVS can be measured within 0. 1 microamperes because little to no leakage current of HV multiplier stages is encountered due to galvanic separation between transformers powering each stage.

The voltage from the dual power supply means is then used to power the x-ray source, such as an x-ray tube. Any suitable x-ray tube 20 known in the art can be employed in the invention. In a typical x-ray tube, a cathode assembly and an anode assembly are vacuum-sealed in a glass envelope. Electrons are generated by at least one cathode filament in the cathode assembly. These electrons are accelerated toward the anode assembly by a high voltage electrical field. The high-energy electrons generate X- rays upon impact with the anode assembly. See, for example, U. S. Patent Nos. 6,075, 839 and 6, 178, 226, the disclosures of which are incorporated herein be reference. In one aspect of the invention, the x-ray tube described below and depicted in Figure 7 is employed in the invention.

Any suitable cathode known in the art can be employed in the present invention.

As one example of a suitable cathode, a continuously-heated metal (tungsten), helical coil is employed in the invention. The tube current-the electron current emanating from the electron emitter given a defined tube voltage-is determined by the temperature of the helix, which is adjusted by the current through the helix. Other emitters can be used, but <BR> <BR> are fashioned from other materials-e. g. , Labs-with a lower specific electron work function than tungsten and, as a rule, have a significantly higher heating capacity than tungsten. With such materials, altering the tube current at the filament is not possible with the same speed as with tungsten. With other (low-temperature) emitters, controlling the tube current occurs differently than by altering the heating current. This can be

performed using an additional electrode, for example a grid connected upstream or a focusing electrode at a different potential than that of the electron emitter. <BR> <BR> <P>The x-ray tube also contains a means for controlling the cathode, e. g. ,<BR> the electrons emitted from the cathode. Any suitable control grid known in the art can be employed in the invention. See, for example, U. S. Patent No. 6,178, 226, the disclosure of which is incorporated herein by reference.

The x-ray tube also contains any suitable anode known in the industry which serves the function described above. See, for example, U. S. Patent No. 6., 075,839, the disclosure of which is incorporated herein by reference.

The various voltages from the dual power supply means are then supplied to power and operate the x-ray tube. The voltage from the HVS system is input to the control grid and the filament/cathode. Thus, the filament/cathode and the control grid are maintained at the same voltage. When both the control grid and the cathode are at the same voltage, there is no voltage gradient, and no electrons are emitted to strike the anode assembly and no x-rays are emitted from the x-ray tube.

The voltage from the FS of the power supply means is split. A lower voltage is fed to the filament of the cathode to heat the filament, as described above. This lower voltage need only be sufficient to heat the filament and, therefore, can range from about 2 to about 5 volts. In one aspect of the invention, this lower voltage is about 4 volts.

A higher voltage from the FS is provided for the control grid voltage described above.

This higher voltage is the differential voltage supplied to the control grid. This higher voltage remains dormant until turned on by the control means, becoming the control voltage. The control voltage is then supplied to the control grid. When this control voltage is added to the voltage existing on the control grid, the voltage on the control grid becomes higher than the filament voltage. This difference in voltage then causes the filament/cathode to emit electrons, such electrons striking the anode, thereby emitting x- rays.

In one aspect of the invention, the X-ray tube described above is mounted within a housing for protecting the surrounding environment from unwanted X-rays. Any housing serving this purpose known in the art can be employed in the present invention.

Preferably, an aluminum housing is employed in the present invention. Optionally, the inside of the housing can be coated or lined with lead.

The x-ray tube can be optionally cooled using any means known in the art such as heat sinks or liquids coolants. One method for cooling the X-ray tube is to fill the housing with oil. The oil not only provides electrical insulation, but it also absorbs the heat generated by the device. Alternatively, other liquids can be used have been developed to use in place of oil. For example, sulfur hexaflouride (SF6) can be employed in place of the oil. Other types of insulating liquids can likewise be employed.

As the coolant liquids are not desired to be present in certain areas, a sheath can be provided to protect those areas from the oil.

The device described above is extremely portable, yet a very powerful, for XRF analysis. The device of the invention is not limited to any specific XRF analysis. Any type of XRF, such as total reflection x-ray fluorescence (TXRF) or energy-dispersive x- ray fluorescence (EDXRF), can be employed in the invention.

Having described the preferred aspects of the invention, it is understood that the invention defined by the appended claims is not to be limited by particular details set forth in the above description, as many apparent variations thereof are possible without departing from the spirit or scope thereof.