Selectable wavelength X-ray source, spectrometer and assay method

Claim 2

In a method for analyzing the composition of a substance by X-ray fluorescence analysis, the steps comprising: producing primary X-rays by directing charged particles to a selected one of a plurality of primary targets which are disposed at separate locations on a primary target plate and each of which has a different composition, the primary X-rays including a wavelength characteristic of the material of the selected primary target and further including a bremmstrahlung spectrum of many wavelengths, directing said primary X-rays toward a selected one of a plurality of secondary targets which are disposed at separate locations on a secondary target carrier and each of which has a different composition whereby secondary X-rays are emitted from said selected secondary target, said selected one of said secondary targets having a composition which emits characteristic X-rays having a wavelength spectra that produces X-ray fluorescence in a specific possible constituent element of said substance, and said selected one of said primary targets being of different composition than said selected one of said secondary targets and being selected to produce primary X-rays which promote said characteristic X-ray emission by said selected secondary target, irradiating said substance with said secondary X-rays, and detecting the wavelength of characteristic fluorescent X-rays emitted by said substance in response to said irradiation thereof to enable identification of at least one constituent element thereof.

Claim 3

The combination of steps defined in claim 1 further comprising the step of selecting a primary target sufficiently thick to absorb at least a substantial portion of said bremmstrahlung while being sufficiently thin to emit said secondary X-rays by fluorescence from the surface of said selected primary target which is opposite from the surface thereof which intercepts said charged particles.

Claim 4

The combination of steps defined in claim 1 comprising the further step of sequentially irradiating said substance with secondary X-rays of different specific wavelengths produced by different specific combinations of said primary and secondary targets including primary and secondary target combinations which are of unlike composition.

Claim 5

The combination of steps defined in claim 1 comprising the further steps of sequentially directing said charged particles to each of said plurality of primary targets and sequentially directing said primary X-rays produced at each primary target during said charged particle irradiation thereof to each of a plurality of said secondary targets whereby the wavelength spectrum of said secondary X-rays is sequentially shifted.

Claim 6

The combination of steps defined in claim 1 comprising the further steps of initially irradiating said substance with an X-ray spectrum including a large number of wavelengths while detecting the wavelengths of X-ray fluorescence from said sample in order to tentatively identify the probable constituents thereof, and subsequently irradiating said substance with secondary X-rays from at least one specific combination of said primary and secondary targets selected to produce secondary X-rays having a wavelength which optimizes X-ray fluorescence of at least one of said probable constituents.

Claim 7

An X-ray fluorescence analysis spectrometer comprising: an X-ray source having means for producing any selected one of a plurality of different specific predetermined X-ray spectra, said X-ray source having a plurality of primary targets each of different composition and means for directing accelerated charged particles to any selected one of said primary targets to produce primary X-rays which include bremmstrahlung and which include specific wavelengths characteristic of the material of the selected primary target, said X-ray source having a plurality of secondary targets each of different composition and means for directing said primary X-rays from any selected one of said primary targets to any selected one of said secondary targets to produce secondary X-rays thereat that have one of said specific predetermined X-ray spectra, said X-ray source further having means for preventing primary X-rays from a selected primary target from reaching ones of said secondary targets other than said selected secondary target, means for directing any selected one of said predetermined X-ray spectra to a substance to be analyzed, and an X-ray detector disposed for detecting characteristic fluorescent X-rays emitted from said substance.

Claim 8

An X-ray fluorescence analysis spectrometer comprising: an X-ray source having means for producing any selected one of a plurality of different specific predetermined X-ray spectra, said X-ray source having a plurality of primary targets each of different composition and means for directing accelerated charged particles to any selected one of said primary targets to produce primary X-rays which include bremmstrahlung and which include specific wavelengths characteristic of the material of the selected primary target, said X-ray source having a plurality of secondary targets each of different composition and means for directing said primary X-rays from any selected one of said primary targets to any selected one of said secondary targets to produce secondary X-rays thereat that have one of said specific predetermined X-ray spectra, said X-ray source further having means for preventing primary X-rays from a selected primary target from reaching ones of said secondary targets other than said selected secondary target, means for directing any selected one of said predetermined X-ray spectra to a substance to be analyzed, and an X-ray detector disposed for detecting characteristic fluorescent X-rays emitted from said substance.

Claim 9

The combination defined in claim 6 wherein said selected primary target is disposed to intercept bremmstrahlung directed toward said selected secondary target and is proportioned to absorb at least a substantial proportion of said bremmstrahlung while emitting said primary X-rays by X-ray fluorescence.

Claim 10

The combination defined in claim 6 wherein at least one of said primary targets has a surface positioned to receive said charged particles and to emit said primary X-rays from the same surface toward said secondary target including said bremmstrahlung and said characteristic wavelengths, and wherein said secondary target has a surface positioned to intercept said primary X-rays and is proportioned to absorb bremmstrahlung therein while emitting said secondary X-rays toward said substance by X-ray fluorescence from another surface.

Claim 11

The combination defined in claim 6 wherein said means for pReventing primary X-rays from reaching ones of said secondary targets other than said selected secondary target comprises a radiation absorbent collimating means disposed between said primary and secondary targets for intercepting primary X-rays from said selected primary target which are directed toward secondary targets other than said selected secondary target and having at least one radiation transmissive passage for transmitting said primary X-rays from said selected primary target to said selected secondary target.

Claim 12

The combination defined in claim 6 further comprising motor means for shifting any selected one of said secondary targets into position for receiving said primary X-rays from any selected one of said primary targets in response to a signal indicative of a predetermined combination of primary and secondary targets.

Claim 13

The combination defined in claim 6 wherein said primary targets are spaced apart along a circular arc and wherein said secondary targets are spaced apart along a coaxial circular arc on a rotatable member whereby said member may be rotated to bring any selected one of said secondary targets into alignment with any selected one of said primary targets and said means for preventing primary X-rays from reaching ones of said secondary targets other than said selected secondary target comprises a radiation absorbent element disposed between said primary targets and said rotatable member and having a plurality of radiation transmissive passages spaced apart along another circular arc which is coaxial with the arcs of said primary and secondary targets.

Claim 14

The combination defined in claim 6 further comprising a self-cycling system for said X-ray source, said self-cycling system having means for sequentially directing said charged particles to predetermined specific ones of said primary targets, and having means for shifting predetermined specific ones of said secondary targets into postion to receive said primary X-rays from predetermined specific ones of said primary targets to produce a predetermined sequence of said secondary X-ray spectra.

Claim 15

The combination defined in claim 12 wherein said self-cycling system further comprises means for controlling said X-ray source to initially irradiate said substance with a polychromatic X-ray spectrum, means coupled to said detector for analyzing the wavelength spectrum of characteristic X-ray fluorescence from said substance in response to said polychromatic irradiation thereof to identify wavelength characteristic of specific elements, logic circuit means for controlling said X-ray source to sequentially irradiate said substance with a plurality of specific secondary X-ray spectra each selected to cause strong X-ray fluorescence from a particular separate one of said specific elements, and means for indicating the amount of characteristic fluroscent X-rays of each of said elements which are detected during said irradiation of said substance by said specific secondary X-ray spectra.

Claim 16

The combination defined in claim 12 further comprising an additional plurality of primary targets each having a composition similar to that of an associated separate one of said plurality of primary targets, an additional plurality of secondary targets each having a composition similar to that of an associated separate one of said secondary targets, a plurality of monitor X-ray detectors each positioned to receive and detect secondary X-rays emitted from an associated separate one of said additional secondary targets, and wherein said self-cycling system has means for momentarily diverting said charged particles from a selected primary target to the one of said additional primary targets associated therewith to cause the associated one of said monitor detectors to produce a signal indicative of the radiation flux being directed to said sample and has means for adjusting the energy of said charged particles if said detected radiation flux differs from a predetermined valUe.

Claim 17

The combination defined in claim 12 wherein said self-cycling system further comprises means for suppressing acceleration of said charged particles to said primary targets during periods when said means for directing said charged particles is in the process of redirecting said particles from one selected primary target to another selected primary target.

Claim 18

The combination defined in claim 12 wherein said self-cycling system further comprises means for suppressing acceleration of said charged particles to said primary targets during periods when said means for shifting said secondary targets is in the process of shifting a secondary target.

Claim 19

The combination defined in claim 12 wherein said self-cycling system further comprises means for suppressing accelaration of said charged particles to said primary targets during periods when said detector is in the process of responding to a fluorescent X-ray count from said substance.

Claim 20

An X-ray fluorescence analysis spectrometer comprising: an X-ray source having means for producing any selected one of a plurality of different specific predetermined X-ray spectra, said X-ray source having means for producing an accelerated charged particle beam and having a plurality of spaced apart targets each of different composition and means for directing said charged particles to any selected one of said targets to produce X-rays thereat which have different X-ray spectra at different ones of said targets, means for supporting a substance to be analyzed in position to receive said X-rays produced at said selected ones of said targets, an X-ray detector disposed for detecting characteristic fluorescent X-rays emitted from said substance in response to said irradiation thereof, and a self-cycling system coupled to said detector and to said X-ray source and having means for controlling said X-ray surce to initially irradiate said substance with a polychromatic X-ray spectrum and means coupled to said detector for analyzing the wavelength spectrum of characteristic X-ray fluorescence from said substance in response to said polychromatic irradiation thereof to identify wavelengths characteristic of specific elements, said self-cycling system further having logic circuit means controlling said X-ray source to sequentially irradiate said substance with a plurality of specific X-ray spectra each selected to cause strong X-ray fluorescence from a particular separate one of said specific elements, and further having means for registering a value having a magnitude proportional to the amount of characteristic fluorescent X-rays of each of said elements which are detected during said irradiation of said substance by said specific X-ray spectra.

Claim 21

An X-ray fluorescence analysis spectrometer comprising: an X-ray source having means for producing any selected one of a plurality of different specific predetermined X-ray spectra, said X-ray source having means for producing an accelerated charged particle beam and having a plurality of spaced apart targets each of different composition and means for directing said charged particles to any selected one of said targets to produce X-rays thereat which have different X-ray spectra at different ones of said targets, means for supporting a substance to be analyzed in position to receive said X-rays produced at said selected ones of said targets, an X-ray detector disposed for detecting characteristic fluorescent X-rays emitted from said substance in response to said irradiation thereof, and a self-cycling system coupled to said detector and to said X-ray source and having means for controlling said X-ray surce to initially irradiate said substance with a polychromatic X-ray spectrum and means coupled to said detector for analyzing the wavelength spectrum of characteristic X-ray fluorescence from said substance in response to said polychromatic irradiation thereof to identify wavelengths characteristic of specific elements, said self-cycling system further having logic circuit means controlling said X-ray source to sequentially irradiate said substance with a plurality of specific X-ray spectra each selected to cause strong X-ray fluorescence from a particular separate one of said specific elements, and further having means for registering a value having a magnitude proportional to the amount of characteristic fluorescent X-rays of each of said elements which are detected during said irradiation of said substance by said specific X-ray spectra.