US3701899A - Method of effecting x-ray analyses - Google Patents

Method of effecting x-ray analyses Download PDF

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Publication number
US3701899A
US3701899A US4978A US3701899DA US3701899A US 3701899 A US3701899 A US 3701899A US 4978 A US4978 A US 4978A US 3701899D A US3701899D A US 3701899DA US 3701899 A US3701899 A US 3701899A
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voltage
sample
current
radiation
anode
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US4978A
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Rastislav Voparil
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Chirana Modrany np
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Chirana Modrany np
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N23/00—Investigating or analysing materials by the use of wave or particle radiation, e.g. X-rays or neutrons, not covered by groups G01N3/00 – G01N17/00, G01N21/00 or G01N22/00
    • G01N23/20—Investigating or analysing materials by the use of wave or particle radiation, e.g. X-rays or neutrons, not covered by groups G01N3/00 – G01N17/00, G01N21/00 or G01N22/00 by using diffraction of the radiation by the materials, e.g. for investigating crystal structure; by using scattering of the radiation by the materials, e.g. for investigating non-crystalline materials; by using reflection of the radiation by the materials
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N23/00—Investigating or analysing materials by the use of wave or particle radiation, e.g. X-rays or neutrons, not covered by groups G01N3/00 – G01N17/00, G01N21/00 or G01N22/00
    • G01N23/22—Investigating or analysing materials by the use of wave or particle radiation, e.g. X-rays or neutrons, not covered by groups G01N3/00 – G01N17/00, G01N21/00 or G01N22/00 by measuring secondary emission from the material
    • G01N23/223—Investigating or analysing materials by the use of wave or particle radiation, e.g. X-rays or neutrons, not covered by groups G01N3/00 – G01N17/00, G01N21/00 or G01N22/00 by measuring secondary emission from the material by irradiating the sample with X-rays or gamma-rays and by measuring X-ray fluorescence
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N2223/00—Investigating materials by wave or particle radiation
    • G01N2223/07—Investigating materials by wave or particle radiation secondary emission
    • G01N2223/076—X-ray fluorescence

Definitions

  • the present invention relates to a method of and an apparatus for efi'ecting X-ray analyses, namely spectral as well as diflraction analyses.
  • Spectral analysis is employed for determining a chemical element in a sample, by means of a characteristic X-ray radiation emitted by the sample. it the sample is excitated by X-ray radiation from an X-ray tube, a secondary analysis is concerned. If the sample is excitated directly by the incidence of electrons, a primary analysis is spoken of. in the event of the X-ray radiation from the X-ray tube passing through the sample, an absorption analysis is effected.
  • Diffraction analysis by means of which the fine structure of a sample is determined, regardless of the element contained in the sample.
  • This radiation however, has a low intensity and therefore requires sensitive detectors, such as Geiger-Miiller counters or a detector of the proportional, scintillation or semiconductor type, registering in the form of individual impulses every quantum of X radiation absorbed in the active zone of the detector.
  • An electronic device connected to the detector, counts the impulses, either all of them or, selectively, only those impulses which have an amplitude of a required magnitude and, finally, it evaluates them as a number of impulses during a predetermined measurement period or, in addition, effects their registration.
  • the present invention aims at removing the disadvantages of the heretofore known methods and devices and at efi'ecting an X-ray analysis without the use of analyzing crystals, while achieving a sufficient resolving power.
  • the method of effecting an X-ray analysis consists therein that to an X- ray tube a basic direct voltage is applied approaching the threshold voltage required for the excitation of the analyzed element a spectral analysis for excitation of the element of the anode in a diffraction analysis, and superimposed on this voltage is a sinusoidal alternating voltage which, together with said basic direct voltage in the positive portions exceeds said threshold voltage, whereas in the negative portions it lies below said threshold voltage.
  • the X-ray radiation is transformed into electric current, the dc. component, the alternating current with the frequency of the superimposed sinusoidal voltage and the second harmonic of said current are suppressed, at least one of the higher harmonics, beginning with the third, is amplified and the resulting current indicated.
  • the invention relates further to an X-ray analyzer for carrying out said method, the analyzer comprising an X-ray tube, a detector and an electronic evaluating device, if necessary with a counter, said X-ray tube being attached to a source of high dc voltage.
  • the main feature of the new apparatus resides therein that in the circuit of the source of high dc. voltage, having a value approaching the threshold voltage required for the excitation of the analyzed element, or of the element of the anode, there is a modulator serving for sinusoidal modulation of said high dc. voltage of the source.
  • the electronic evaluating device of the detector is selectively sensitive to a frequency exceeding double the basic frequency of said modulating sinusoidal voltage.
  • the invention is concerned with feeding the anode of an X-ray tube, which represents the source of a continuous radiation, serving for the analysis of the sample, with a smoothed high voltage, approaching the threshold voltage of the K- or L- edge of the excitated sample element to be analyzed.
  • This smoothed high voltage is modulated by (or superimposed thereon is), a small-scale sinusoidal alternating voltage, which in the positive half-waves excites the element, whereas this does not occur during the negative half-waves.
  • the radiation emanating from the sample (or anode) and received by the detector contains as its time func tion primarily a dc. component, further an alternating component whose basic frequency originates from the continuous stray radiation of the sample and from the characteristic radiations of elements having a lower threshold voltage than the element undergoing analysis, further an alternating component whose basic frequency originates from said analyzed element and finally higher harmonics.
  • harmonic frequencies if higher than the second harmonic, are present to a higher degree only in the presence of an element whose threshold excitation voltage equals the anode voltage of the X-ray tube.
  • the electronic evaluating device cooperating with and following the detector is selectively sensitive to the alternating current component and more particularly to one or more higher harmonics, beginning with the third harmonic; the detector indicates on a counter a deflection, depending on the contents of the analyzed element in the sample.
  • the invention affords a number of advantages. In the first place there is a considerable intensity of the detected radiation, simple wiring as well is used as simple components for building up the apparatus, and, in particular, expensive analyzing crystals are fully dispensed with. Moreover the overlapping of Ka and K [3 lines of two elements having neighboring atomic numbers and duplicities caused by reflections of higher order are avoided.
  • FIG. 1 shows in a block diagram the arrangement of an apparatus for effecting a spectral secondary X-ray analysis.
  • FIG. 2 shows in a diagrammatic representation the general idea underlying the invention.
  • FIG. 3 is a block diagram of an apparatus for effecting an absorption analysis
  • FIG. 4 is a similar view showing the arrangement of an apparatus for spectral primary analysis
  • FIG. 5 represents diagrammatically an apparatus for the monochromatization of radiation in a structural analysis
  • FIG. 6 shows in detail the overall arrangement of the wiring in an apparatus shown diagrammatically in FIG. 1
  • FIG. 7 represents a practical example of analyzing an iron-nickel alioy, explaining the operation of the apparatus as well as the generation of the various harmonics.
  • a dc. component Va of a high voltage KV (in the following to be called basic d.c. voltage”) is adjusted on the anode of an X-ray tube in such a way as to produce a voltage approaching or equalling the threshold voltage V0.
  • the threshold voltage of an element is the minimum voltage at which the element begins to be excited and to emit its own characteristic radiation. This voltage determines what is termed the K- or L-edge of the analyzed element.
  • a small scale alternating voltage of a sinusoidal shape is superimposed on said basic dc. voltage Va, said alternating voltage having an amplitude v0 and basic frequency fi.
  • the size of the amplitude of the alternating voltage permits one to chose and adjust on the one hand discerning ability between two elements of near atomic numbers and, on the other hand, the intensity of radiation and sensitivity of the method, as will be clearly understood from the ensuing disclosure.
  • FIG. 1 shows diagrammatically one example of an apparatus for effecting a spectral secondary fluorescent X-ray analysis.
  • a sample 1 receiving radiation from an X-ray tube 5 is thereby excited and emits a characteristic radiation, which is fed to a detector 2.
  • the anode of the X-ray tube 5 is supplied with a high dc. voltage from a source 3. Superimposed on this high dc. voltage by a modulator 4 is an alternating voltage, as explained above and shown in FIG. 2.
  • the radiation from the sample I, received by the detector 2 is evaluated in an electronic evaluation device 6, which is sensitive to one or more higher harmonics, beginning with the third. Attached to the output of the evaluating device 6 is a suitable indicating means 7 such as an indicator or a recorder.
  • FIG. 6 illustrates in detail the arrangement of electric circuits in the aforementioned apparatus, as an example of using the invention for a secondary spectral X- ray analysis.
  • the high voltage source 3 feeding the anode of the X-ray tube 5 comprises an adjustable-ratio autotransformer 10 for adjusting the required voltage on the primary winding of a high voltage transformer 11, whose alternating voltage is rectified behind the secondary winding by a high voltage rectifier l2 and smoothed by a capacitor 13.
  • the actual value of the voltage across the X-ray is measured by a volt-meter 14 with a seriesconnected resistor 15.
  • the anode current of the X-ray tube is measured by a milliameter l6 and controlled by an adjustable resistor 17 inserted in the primary circuit of the filament transformer 18.
  • the superposition of the alternating voltage on the basic dc. voltage is effected by the modulator 4 which, in its simplest arrangement, comprises a transformer 19 fed from the ac. mains 20 over an adjustable-ratio autotransformer 21.
  • the continuous X-ray radiation, produced in the focus on the anode 22 of the X-ray tube 5, is limited by a diaphragm 23 and impinges on the sample 1, from which all radiation components are received by the detector 2.
  • the detector may be of the gas-type, such as a Geiger-Miiller counter or a proportional counter or of the scintillation or semiconductor type.
  • a conventional scintillation detector comprising a fluorescent substance or foil 24, screened off against outer light by a foil made of aluminum or beryllium, further a photo-multiplier 26, whose photo-cathode 27 is fed with high voltage, e.g. IOOOV, supplied by a conductor 28.
  • the detector dynode 29 comprise dividing resistors 30 for the various stages and a resistor 31 for the plate 32 is provided in the detector.
  • the signal, emitted by the detector is passed by a screened conductor 33 into an electronic evaluation device 6.
  • the electronic evaluation device comprises a two-stage amplifier of alternating voltages, with a selective sensitivity for a frequency tuned by two LC-resonance circuits 34 and 35 in the grid and anode circuit of the first amplifying electron tube 36.
  • An output transformer 37 allows the passage of the alternating component of the anode current of the second electron tube 38 only.
  • the resulting alternating current is rectified by a diode 39 and fed to the d.c. indicating means 7, such as a milliameter or a recorder.
  • the fluctuation of measured values can be reduced by increasing the time constant by means of a capacitor 41.
  • the other half-wave of the alternating output current is fed to a resistor 42 over a second diode 43.
  • a coupling condenser 44 permits the passage of alternating components only.
  • a conductor 45 being attached to a plus-voltage, the anodes of both electron tubes and the second grid are supplied with current and the second grid is fed over a resistor 46.
  • the required negative bias of the electron tube grids is obtained by the voltage drop on resistors 47, 48 and blocking capacitors 49 and 50.
  • FIG. 6 and the above disclosure refer to a particular embodiment of the new apparatus, it will be clear to those skilled in the art, that numerous modifications may be effected in connection with various circuits or the arrangement of their parts without departing from the scope of the present invention.
  • FIG. 7 of the accompanying drawings showing a set of diagrams relating to the determination of the contents of iron in nickel by means of a secondary X- ray spectral analysis.
  • the threshold voltages for the emission of K-series radiation of the two elements namely Fe (7,1 KV) and Ni (8,3 KV) are represented in FIG. 7 by straight lines.
  • the d.c. anode voltage across the X-ray tube is adjusted so as to equal the threshold voltage of the element to be determined, i.e. VoFe 7,1KV.
  • Superimposed thereon is a modulating sinusoidal voltage of normal mains frequency and an amplitude l KV, so that the time function of the anode voltage of the X-ray tube is given by a curve marked A in FIG. 7, which is a sinus curve.
  • the curve B in FIG. 7 represents the intensity of radiation, emitted by the tungsten anode of the X-ray tube, when neglecting the absorption of radiation by the window and assuming a constant current flow through the X-ray tube. According to the known law governing the generation of continuous radiation, the latter is proportional to a square of the anode voltage Le. the momentary values of the curve 8 equal the square of the values of the curve A.
  • the curve B is not an exact sine curve any more, but contains also the second harmonics, as is apparent from the curves C produced by resolution of the curve B into two components, namely an alternating component having the basic frequency of the modulator and the second harmonic. Higher harmonics than the second harmonic in the intensity of radiation emanating from the X-ray tube, are not present, which fact can be proved easily, even by calculation.
  • the nickel present in the sample, cannot be excited because the curve A of the anode voltage does not reach, at any moment, the threshold value for nickel VoNi 8,3KV.
  • the detector 2 receives only the radiation scattered by the sample, whose intensity is proportional to the primary radiation impinging on the sample, which means that the curve B C applies also for the radiation entering the detector, the only difference being in the degree of intensity.
  • the registered intensity contains the d.c. component, further the basic frequency f, of the modulator and the second harmonic 2 f,.
  • the indicator 7 indicates an intensity equal zero, because the amplifier is not sensitive to frequencies from 0 to 2f,
  • the invention can be used not only for a spectral secondary fluorescent X-ray analysis, but also for a primary analysis, as well as for absorption analysis.
  • FIG. 3 shows the arrangement of the apparatus for carrying out an absorption analysis.
  • the various parts of the apparatus are similar to those described in connection with FIGS. 1 and 6 and are therefore marked with the same reference numerals.
  • FIG. 4 shows the arrangement of the apparatus for efiecting a primary analysis.
  • This sample 1 forms here part of the anode of the X-ray tube 5 and is excited directly by the impact of the electrons emitted by the cathode of the X-ray tube.
  • the radiation emitted by the anode or sample 1 is fed directly into the detector 2.
  • FIG. 5 shows the arrangement of the apparatus for effecting monochromatization of the radiation, if a structural analysis is carried out.
  • the anode of the X- ray tube 5 contains an element emitting the required characteristic radiation, necessary for effecting the diffraction structural analysis.
  • the dc. component of the high voltage Va is again equal to the exciting edge of the element contained in the anode.
  • the produced modulated radiation is used as a primary beam for a recording structural diffractometer, marked 8 in FIG. 5.
  • the diffractometer 8 comprises the sample I mounted for rotation and the detector 2 placed on a rotatable protractor arm 9. The speed of angular displacement if the detector 2 is double the speed of angular displacement of the sample 1.
  • the detector 2 with the protractor arm 9 is continuously rotated, along with the sample 1, and in the sought reflection angles the so-called diffraction lines are registered.
  • the electronic evaluation device 6 is selectively sensitive to the third and higher harmonics.
  • the disclosed arrangement is advantageous in that the monochromatization occurring in this case as a reduction of the continuous background, is achieved without any intricate adjustment of the geometrical parameters of the system X-ray tube focus monocrystal sample.
  • any desired high discerning power may be achieved.
  • This discerning power is given by the amplitude of the superimposed alternating voltage according to the relation From FIGS. 2 and 7 it is evident, that two elements may be discerned, if the difference of their threshold voltages marked A V is equal to or greater than double the amplitude v0.
  • a method of effecting X-ray analysis of a sample containing a specified element comprising the steps of:

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US4978A 1969-01-27 1970-01-22 Method of effecting x-ray analyses Expired - Lifetime US3701899A (en)

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DE (1) DE2002939C3 (de)
FR (1) FR2029496A1 (de)
GB (1) GB1249795A (de)
NL (1) NL7001078A (de)

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4815116A (en) * 1981-09-17 1989-03-21 Process Automation Business, Inc. Method and apparatus for x-ray analysis of rapidly moving multicomponent materials
US4980901A (en) * 1988-09-09 1990-12-25 The Titan Corporation Apparatus for and methods of detecting common explosive materials
US5365563A (en) * 1992-02-29 1994-11-15 Horiba, Ltd. Fluorescent X-ray quantitative analysis apparatus
NL1003447C2 (nl) * 1995-06-27 1997-08-26 Shimadzu Corp Röntgendiffractometer.
US5778041A (en) * 1983-10-13 1998-07-07 Honeywell-Measurex Corporation System and process for measuring ash in paper

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
SE428974B (sv) * 1979-02-07 1983-08-01 Nils Johannes Baecklund Sett att medelst rontgenstralning meta halten av ett forutbestemt emne i ett prov

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2745019A (en) * 1952-10-08 1956-05-08 Philips Corp X-ray intensity measuring system
US3114832A (en) * 1960-07-28 1963-12-17 Radiation Counter Lab Inc X-ray spectroscopic system comprising plural sources, filters, fluorescent radiators, and comparative detectors
US3146347A (en) * 1961-08-25 1964-08-25 Lab For Electronics Inc Apparatus for analyzing material by excited x-rays

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2745019A (en) * 1952-10-08 1956-05-08 Philips Corp X-ray intensity measuring system
US3114832A (en) * 1960-07-28 1963-12-17 Radiation Counter Lab Inc X-ray spectroscopic system comprising plural sources, filters, fluorescent radiators, and comparative detectors
US3146347A (en) * 1961-08-25 1964-08-25 Lab For Electronics Inc Apparatus for analyzing material by excited x-rays

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4815116A (en) * 1981-09-17 1989-03-21 Process Automation Business, Inc. Method and apparatus for x-ray analysis of rapidly moving multicomponent materials
US5778041A (en) * 1983-10-13 1998-07-07 Honeywell-Measurex Corporation System and process for measuring ash in paper
US5854821A (en) * 1983-10-13 1998-12-29 Honeywell-Measurex Corporation System and process for measuring ash in paper
US4980901A (en) * 1988-09-09 1990-12-25 The Titan Corporation Apparatus for and methods of detecting common explosive materials
US5365563A (en) * 1992-02-29 1994-11-15 Horiba, Ltd. Fluorescent X-ray quantitative analysis apparatus
NL1003447C2 (nl) * 1995-06-27 1997-08-26 Shimadzu Corp Röntgendiffractometer.

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DE2002939B2 (de) 1974-11-21
DE2002939C3 (de) 1975-07-03
DE2002939A1 (de) 1970-08-06
FR2029496A1 (de) 1970-10-23
GB1249795A (en) 1971-10-13
NL7001078A (de) 1970-07-29

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