US2924715A - X-ray analysis apparatus - Google Patents

X-ray analysis apparatus Download PDF

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US2924715A
US2924715A US588898A US58889856A US2924715A US 2924715 A US2924715 A US 2924715A US 588898 A US588898 A US 588898A US 58889856 A US58889856 A US 58889856A US 2924715 A US2924715 A US 2924715A
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radiation
enclosure
gas
region
detection
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Charles F Hendee
Fine Samuel
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US Philips Corp
North American Philips Co Inc
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US Philips Corp
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Priority to NL217744D priority patent/NL217744A/xx
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Priority to FR1176408D priority patent/FR1176408A/fr
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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
    • G01N23/22—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
    • 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
    • G01N23/20008—Constructional details of analysers, e.g. characterised by X-ray source, detector or optical system; Accessories therefor; Preparing specimens therefor
    • G01N23/20025—Sample holders or supports therefor
    • 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
    • G01N23/207—Diffractometry using detectors, e.g. using a probe in a central position and one or more displaceable detectors in circumferential positions
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J47/00—Tubes for determining the presence, intensity, density or energy of radiation or particles
    • H01J47/06—Proportional counter tubes
    • 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

  • This invention relates to a method and system for the chemical analysis of materials by means of X-radiation.
  • partition or separation means to isolatethe X-ray generating and detector regions containing the different gases, which partition had the form'of a very thin window of, for example, beryllium, which was gas-permeable.
  • Employing such an extremely thin Window was essential in order to enable this fiuorescent X-radiation, which is commonly known as sof X-radiation when it is characteristic of the elements in the third and fourth periods of the periodic table, i.e., the K-radiations' of these elements, which lie in the wavelength range of about 12. to 2 Angstroms, to enter the detector. Operation of the system thus described is excellent for the range of elements in the third and fourth periods.
  • the primary object of the present invention is to provide a system and method for chemical analysis of materials by means of X-radiation and'which is capable of analyzing the fluorescent X-r'adiation produced by elements in the second period of the periodictable.
  • the system or apparatus of the invention comprises an enclosure having a fir'st regionin whicHultra-so'ft X radiation is generated and, if desired, monochromati'zed, collimated, or both, and a second region in which the ultra-soft X-radiation is received and detected to produce in an output circuit elec- 2,924,715 Patented Feb. 9, i960 2 trical signals which contain information concerning the intensity and the wavelength of the incident ultra-soft X-radiation.
  • X-ray optics region is defined to denote, broadly, any and all means within the first region for generating ultra-soft X-radiation and for utilizing and/or operating on said X-radiation for some particular purpose.
  • these means may; include a source of X-radiation, such as an X-raytube or artificially-radioactive source. It may also include collimating means or split systems for shaping a beam of X-radiation fora particular purpose.
  • dispersive means such as a single crystal or grating for separating the radiation into its individual wavelengths.
  • detection region denotes the second region in the enclosure in which X-radiation may be absorbedby an ionizable'gas medium therein, thereby to produce ion pairs which can be collected by a suitable electrode system and thus produce an electrical pulse in an output circuit.
  • the apparatus of the invention utilizes the principle of controlled absorption and transmission of the ultra-soft X-radiation in the X-ray optics and detection-regionsso as to optimize the detection efficiency for a particular wavelength of the radiation. The manner by which this is accomplished will be explained in greater detail hereinafter.
  • the pressure of the gas atmosphere common to both the X- ray optics and detection regions is varied or controlled to maximize the sensitivity of the detection region for a particular X-radiation.
  • the ratio of X-ray optics path length to detection path length in the two regions is" slowly varied While continuously detecting the incident radiation thereby to produce output information, which when properly uti. lized, enables the ultra-soft X-radiation t'o be directly analyzed.
  • Fig. 1 illustrates, somewhat schematically, one form of apparatus accordihg to the invention for analyzing the principal fluorescent radiations of elements in the second period of the periodic table;
  • Fig. 2 is an elevational view of the apparatus shown in Fig. 1 along the line 22;
  • Fig. 3 is a graph showing counting efiiciency curves in the detection region" for the K-radiations of severalbele ments in the second period;
  • Fig. 4 illustrates a modification of the apparatus shown in Big 1, in which the ratio of X-ray optics to detection path lengths may be varied;
  • Fig. 5 is a graph of data obtained by operating thesystem illustrated in Fig. 4 in a particular manner.
  • Fig. 1 shows one form of X+ray analysis system in accordance with the invention.
  • the system shown comprises a housing or enclosure 5, which is substantially gas-tight and which is provided-with a gas-tightdoor' 6 afiording access to the interior.
  • Within the housing 5 is mounted an X-ray,
  • the elements constituting a specimen to be analyzed into pared by techniques well-known in this art is mounted in a position to be irradiated by the X-radiation emanating from the tube 7, which irradiation excites the elements constituting the specimen 8 into generating their characteristic X-radiations in all directions therefrom.
  • the specimen 8 contains one or more elements in the second period of the periodic table, which elements thus produce characteristic fluorescent X-radiation, i.e., their K-radiations, which are ultra-soft in character.
  • typical wavelengths for these radiations lie in the range of about 200 to 12 Angstroms.
  • a single crystal 10 which may, for example, be of gypsum, is-mounted for rotation about an axis 11 and is positioned to receive some of the fluorescent X-radiation generated by the specimen 8.
  • the single crystal 10 reflects or refracts selected wavelengths of that fluorescent X-radiation in particular directions relative to the surface thereof, as is shown by the dotted lines in the drawing.
  • a slit system 12, shown schematically, is mounted for rotation about the same axis 11 as the single crystal 10.
  • suitable mechanical couplings shown schematically as a pair of gears 13
  • the slit system 12 is caused to rotate about the axis 11 at twice the angular velocity as that of the crystal 10.
  • 2,449,066 describes a conventional system of this general type wherein this 2 to 1 rotational relationship between a crystal and a detector may be obtained.
  • the angular position of the single crystal 10 and the slit system 12 relative to the specimen 8 determines which wave lengths of a plurality thereof present in the radiation generated at the specimen 8 will be passed on to the remainder of the system.
  • This angular position may be indicated by a pointer and scale as shown at 15.
  • a blocking or barrier member 16 is mounted between the X-ray tube 7 and specimen 8, and between the specimen 8 and the slit system 12, which blocking member serves to prevent direct radiation from the tube 7 from being incident on the crystal 10, and also prevents fluorescent X-radiation from the specimen 8 from passing directly through the slit system 12 without impinging first on the crystal 10.
  • the elements described above are all located within the X-ray optics region of the system. r
  • ultra-soft X-radiation i.e., the specimen 8
  • portions of the X-radiation e.g., monochromatizing or collimating the utra-soft X-radiation for various purposes, i.e., the elements 10 and 12.
  • the right half of the system shown in Fig. 1 comprises the detection region.
  • the detection region comprises a cylindrical, slightly-curved, conducting enclosure 19 constituted by metal walls 20, 21, 22 and 23 of the housing, and a wire 24, for example, of 0.020 inch in diameter, extending through the center of said conducting enclosure 19 but insulated therefrom by means of an insulating head 25 sealed in the wall 22 of the housing.
  • entrance into the detection region is afforded by an elongated slit 26 located in the wall 21 of this conducting enclosure 19.
  • the conducting enclosure 19 and the wire 24 constitute cathode and anode electrodes, respectively, of a Geiger- Mueller type of radiation detector or counter.
  • .means 27 are provided for applying a relatively high potential, which can be varied, between the anode wire 24 and the cathode enclosure 19.
  • a resistor 28 in series with said potential source 27 is a resistor 28, across which electrical output signals may be den'ved in the usual way.
  • the electrical signals which may be in the form of pulses, are utilized in the normal manner, such as by counting them and recording the results.
  • a suitable ionizable gas is provided within the housing 5. This is accomplished by means of a source or supply of gas 30, which is coupled by way of a suitable pressurecontrol means 31, such as a low-pressure regulator, to the housing 5.
  • a conventional form of pump 32 for first exhausting, if desired, the air within the housing 5, or for reducing the pressure of the gas within the housing 5 below atmospheric pressure.
  • a pressure indicator 32 measures and indicates the gas pressure within the housing. It will be observed that the X-ray optics and detection regions freely communicate with one another through the unimpeded slit 26, and thus a common gas at the same pressure is present in both regions of the system.
  • the cathode and anode electrodes in the detection region have the form illustrated to provide a large angular receiving area, so that for every position of the crystal 10 and slit system 12 within a limited angularrange, the reflected radiation will enter a sensitive and responsive volume of the detection region.
  • the ultra-soft, fluorescent X-radiation generated at the specimen 8 traverses an, optical path to the single crystal 10.
  • Certain Wavelengths of that fluorescent X-radiation are selected by the single crystal 10 and the slit system 12 and passed to the slit 26 constituting an entrance to the detection region.
  • scattered X-radiation present everywhere in the X-ray optics region is also entering the detection region through the slit 26.
  • the total opticalpath .for' the ultra-soft, fluorescent X-radiation in the X-ray. optics region is equal to about L as shown in the drawing.
  • Q The radiation traversing that path enters the detection region through the slit 26.
  • the path in the detection region traversed by the incident radiation is approximately equal to L Any radiation not absorbed by the gas present in the detection region is either lost in the. remote wall 20 or passes through that Wall 20 and out, of the system.
  • the wall 20 may be constituted by some very thin, conductive material, such as beryllium, which has a retalively high transmission toX-radiation. Any ultrasoft X-radiation absorbed by the gas in the detection region will produce ion pairs, which will be attracted to and collected by the anode. and cathode electrodes therein, thereby to generate electricabsignals in the output circuit across the resistor 28.
  • the same gas present in thedetection region is also present in the .X-ray optics region; yet this gas in the X-ray optics region apepars to transmit the ultra-soft X-radiation to the direction region whereas the same gas in the detection region absorbs the same radiation to produce usableelectrical information.
  • the reason for this apparent anomaly follows as. a direct consequence of ;one of the chief features of the invention, namely, to select a geometry for the X-ray optics'and detection regions at which certain desired radiations are transmitted to and absorbed in the detection region whereas other undesired radiations are absorbed either in the X-ray optics region or pass completely out ofthe system.
  • geometric discrimination against unwanted radiations is what could be termed geometric discrimination against unwanted radiations. The following discussion will make this clearer.
  • the relative ratio of absorption'to transmission of a particular path length of a gas depends solely on the wavelength of radiation involved, and the composition and pressure of the gas. In general, for a given path length, the absorption of the gas can be increased by increasing its pressure or by changing its composition to include a higher atomic number element. On the other hand, for
  • the absorption can be increased by increasing the path length in said gas traversed by the radiation.
  • the invention utilizes these principles to provide geometric discrimination against unwanted radiation being absorbed and thus producing electrical information in the detection region. This is accomplished by providing an X-ray optics path of finite length and a detection region of finite length in a me determined relationship.
  • radiation comprising a plurality of soft and hard components, i.e., soft being longer wave-length radiation and hard being shorter wavelength radiation, traverses the finite X-ray optics path and the finite detection path, it is found that the absorption along this path is wavelength dependent.
  • the softer wavelengths will be principally absorbed in the X-r-ay optics region and .thus produce only a very low counting efi'iciency in the detection region.
  • the very hard radiation will be absorbed only slightly in the X-ray optics and detection regions, and thus pass essentially out of the system.
  • the electrical output information from the detection region which depends upon its relative absorption efiiciency comprises mainly information about the intermediate radiation and contains a correspondingly smaller quantity of information about the softer and harder radiations.
  • the geometry in thesystem of the invention provides selective absorption in the X-ray optics region to separate the wavelengths present in the generated ultra-soft X-radiation, thereby to provide information primarily about the wavelength desired.
  • L the length of the X-ray optics path
  • the X-ray optics path must be at least one cm. in length.
  • the detection region will be located as close as feasible'to the source of the ultra-soft X-radiation, and thus the upper limit of L will depend on the number and size of the elements present in the X-ray optics region.
  • the pressure of the gas within the housing and common to both the X-ray optics and detection regions is controlled, thereby to vary the selective absorption ofthe overall path and thus optimize the production of information from the detection region about a different wavelength of radiation.
  • the counting efiiciency in the detection region will be a common housing 5 is reduced, which reduction results in a lower absorption of saidlonger wavelength radiation in the X-ray optics region and thus a shift of the maxi mum counting efliciency toward the longer wavelength region.
  • the highest counting eificiency for this longer wavelength radiation now obtains in the detection region.
  • the relationshipbe'tween the counting efiiciency to a particular wavelength ofradiation in the detection region, the pressure and composition of the common gas, and the geometry of the system can be expressed mathematically in the following way:
  • F is the fractional counting efiiciency of the X-rays that enter the system
  • Equation 1 is the mass absorption coefiicient in the cm. /gm.
  • p is the density of the common gas at standard conditions of room temperature and atmospheric pressure in gm./ cm.
  • P is the pressure of the gas in the system in atmospheres or fractions of an atmosphere
  • Li is the optics path length in cm.
  • L is the detection path length in cm.
  • Subscripts m and, d have been attached to the two Greek letters p to avoid confusion. Otherwise, they are the conventional symbols used in this art. From Equation 1, it can be shown that:
  • Equation 2 9 1M 1, L3 +ln(1 where F max is the maximum possible attainable etficiency of counting in the detection region and L is the overall path length and equal to L -+L
  • F max is the maximum possible attainable etficiency of counting in the detection region
  • L is the overall path length and equal to L -+L
  • Equation 2 The significant point derivable from Equation 2 is that the maximum counting 'region, and the length L of the detection region.
  • Equations 1 and 2 for maximum counting eflleieney yields I the following:
  • control number the product of the gas pressure and the detection path length.
  • This control number is a function of the geometry of the system for a particular gas and wavelength, and denotes those combinations of pressures and detection path length at which the maximum counting efficiency for a particular radiation is realized. Otherwise stated, for every combination of pressures and path lengths which satisfy Equation 3, the system is tuned to maximum counting efiicieney for a particular radiation.
  • other considerations dictate limits for these control numbers, and in accordance with the invention, only those systems which provide control numbers in the range of 0.01 to 400 are considered within the scope of the invention.
  • the factors which dominate the construction of a practicable system are the range of gas pressures in the enclosure which can be readily produced by commerciallyavailable'equipment, the length L of the X-ray optics
  • the pressures of the common gas should lie in the range between about 0.01 and 2 atmospheres.
  • detectors of the Geiger-Mueller type are readily available which operate with normal values of potentials, and are of reasonable size. Pressures below the lower limit are harder to maintain and less controllable; pressures above the two atmosphere limit render more difficult construction of a gas-tight enclosure.
  • ragard to L the length of the detection region, a feasible range of values lies between about 1 cm. and about 200 em.
  • the minimum value is again dictated by reasons demanding a clear separation between the detection and X-ray optics regions. If L were made too small, then absorption events occurring at its border or even within its active region may result in some of the ion products being lost and thus not contributing to the formation of the electrical pulses.
  • the maximum value is provided to minimize the eumbersomeness of the apparatus.
  • the dimension of L will depend upon the elements present in the X-ray optics region. For the situation illustrated in Fig. 1, wherein a. specimen, a dispersing device and a slit system are mounted in the X-ray optics region, obviously the path length of the latter is considerable, for example, possibly 20 cm. or higher.
  • the dimension of the X-ray optics path length in the embodiment illustrated in Fig. 4, which will be later described, is not as large.
  • the radiations for which the system is tuned are, of course, the K-radiations of the elements in the second period of the Periodic Table.
  • the only remaining unknown is a suitable gas with which the results of the invention may be achieved.
  • a suitable gas with which the results of the invention may be achieved.
  • Helium is clearly the preferred gas, because it provides a fairly high counting effieiency for the ultra-soft X-radiations and within a readily-obtained range of pressures 'and for any number of practicable geometries. 'Several systems of the invention will now be described in detail.
  • tuning for carbon occurs at a pressure of 0.105 atm.; for nitrogen, at a pressure of 0.277 atm.; for oxygen, at a pressure of 0.608 atm.; and for fluorine, at a pressure of 0.918 atm.
  • a counting eflieiency of 50% of the ultra-soft X-radiations in the detection region is realized with a range of helium pressures of 0.04 to about 0.9 atmosphere.
  • the control numbers for the foregoing example range from 0.943 to 21.23. It will be observed from this example that the length of the X-ray optics region is fairly small and may be inadequate for the provision of a dispersing system as illustrated in Fig. 1. This can be assisted by increasing the ratio of L to L though a sacrifice in counting efiiciency will result.
  • Example II illustrates such a system.
  • Curve represents the counting efliciency against pressure for the K-radiation of oxygen; curve 46, that for nitrogen; curve 47, that for carbon; and curve 48, that for boron. It will be observed from Fig. 3 that each of the curves exhibits a maximum point or peak for some particular pressure of the helium. In other words, by adjusting the helium pressure within the housing to a predetermined value, it is found that, for the geometry indicated above, the counting efiiciency in the detection region is a maximum for a particular wavelength of radiation.
  • the peaks of these elements 5 to 8, which are adjacent in the second period, are fairly widely spaced apart, so that at a particular pressure of the helium, the high counting effieiency corresponding to the selected wavelength contrasts markedly to the relatively lower counting efiieiency for the characteristic fluorescent radiation of an adjacent element in that same period.
  • the counting efiicieney in the detection region for the K-radiation of nitrogen is 25%.
  • the counting efficiency in the detection region for the K-radiation of oxygen will be only 19%, the counting efiiciency for the 'K-radiation of carbon 13%, and the counting efficiency for the K-radiation of boron practically zero.
  • the information present in the electrical pulses appearing in the output circuit coupled to the detection region is representative primarily of the intensity or the K-radiations of nitrogen.
  • the reasons'for thesernarked difierences in counting efficiency for'the K-radiations or adjacent elements inthe second period which are also the chief reasons for the system being operable essentially only inthe ultra-soft and adjacent X-radiation regions; are the rather large differences in wavelength betweenthe K-radiations of these very low number atomic elements, 'andthe exceedingly large differences in value "of the mass absorption coeflicients for these wavelengths of'diflerent detecting gases.
  • the invention is operable only with those detecting gases.
  • having linear absorption coefiicients at atmospheric pressure which fall in the range of the corresponding coefficients of the ele ments neon and below in atomic number, and thus includes, a low weight organic detecting gas such as methane.
  • the linear absorption coeflicient is the product of the mass absorption coeificient and the density p at atmospheric pressure.
  • Fig. 4 illustrates another form of the system of the invention, which'is capable of being operated in a somewhat difierent fashion, -In particular, the system in Fig. 4 comprises" an enclosure 50, which is gas-tight, and which houses a source of ultra-soft Xrradiation 51.
  • This source 51 may be constituted by a fluorescing specimen containing elements in the second period. It is assumed that source 51 produces ultra-soft X-radiation of at least two different wave-lengths.
  • Mounted within the enclosure is a counter 53 defining a given detection region of finite length L
  • the counter 53 comprises a hollow, metal cylinder 54, to which is connected at the top an insulated portion 55.
  • anode wire 56 which extends along the axis of the cylinder '54. Coupled to the anode wire 56 and the cylinder 54 is an output circuit including a source of potential 57 and aresistor 58.
  • the cylinder 54 constitutes a cathode electrode, which, together with the anode wire 5'6, constitutes a Geiger-Mueller type of detector, Whereby the production of ion pairs by a gas absorbing incident radiation will produce output pulses across the resistor 58 when the ion pairs are collected by the cathode and anode electrodes.
  • the counting action in the enclosure 50 occurs within the detection region along an average path length of L
  • the X-ray optics region which is the region between the source of the ultra-soft X-radiation and the detection region, has, as shown in Fig. 4, an average pathlength equal to about L
  • the rear of the cylinder 54 is open, so that radiation not abso'rbed within the region of the cylinder 54 will pass out of the detection region to an area in the enclosure where it will no longer be significant.
  • Thequantity of absorption occurring along the overall path constituted by path lengths L and L depends upon the quality of the radiation emanating from the source 51.
  • the softer portions of the radiation will be principally absorbed in the "X-ray optics region, thereby producing a relatiyely low number of counts or pulses in the output circuit.
  • the harder radiations will pass through the X-ray optics and detection regions and again produce a relatively small number of counts in the output circuit.
  • the counting efficiency of the intermediate radiations is the highest andthus produces the greatest number of output pulses.
  • the system illustrated in Fig. 4 includes means for displacing the counter 53 along the overall path so as to enable the ratio of X-ray optics to detection path lengths Il /L to be varied as desired.
  • These means may comprise a member 60 mounted for movement in a remote wall 61 of the enclosure 50 and including a rack portion 62 on its underside external to the enclosure. Coupled to that rack 62 is a pinion 63, which in turn is rotatable or actuable by a motor 64 of the usual form.
  • Qoupled to the enclosure also is a supply of counting gas 66, for example, of helium.
  • a conventional pump 68 is also connected to the enclosure.
  • the system illustrated in Fig. 4 is a non-dispersive system in which geometric discrimination is utilized to separate the wavelengths emanating from the ultra-soft X-radiation source 51.
  • a pressure of helium may be selected at which the system' is tuned to a particular wavelength of radiation,i.e., the sensitivity of the counter 53 to that particular wavelength is optimized, whereas its sensitivity to other wavelengths is reduced.
  • the provision of the means for translating the counter 53 along the axis of the system, so that the ratio of X-ray optics to detection path lengths may-be varied, offers the additional advantage of optimizing within a given range of pressures the counting efficiency of the counter 53.
  • the coupling means 70 may provide these changes simultaneously. That is to say, coupling means of any conventional form may be provided at which the motor 64 displaces the counter 53 to a predetermined location with.
  • the apparatus illustrated in Fig. 4 has the additional feature that it provides a very simple yet fairly accurate method of analyzing ultra-soft X-radiation containing a plurality of unknown wave'lengths.
  • This method involves the following steps.
  • the counter 53 is first located at the end of the'enclosure 50 remote from the source 51. Then, while the radiations traverse the optical path along the center of the enclosure 50, the counter 53 slowly scans spacewise along the optical path from the remote end to a position adjacent the source 51. In other words, the counter 53 is slowly translated from one end of the enclosure 50 to the opposite end. Meanwhile, the counter 53 continuously counts the ion pairs produced by absorption within the gas enveloped by the counter 53 during its movement along the optical path.
  • a graph (Fig. 5) can be plotted in which the logarithm of the counting rate is plotted versus the position of the counter 53 along the axis of the enclosure 50. This distance is referred to by the reference letter Z in Fig. 4, with Z decreasing as the counter 53 approaches the source 51.
  • a curve 72 will result from the steps set forth above, if the source 51 is producing ultra-soft X-radiation of two different wave-lengths. The curve 72 results from the different quantities of absorption of the different radiations which occur along the combined path.
  • graphical means one may obtain the slopes of the extremes of the curves 72, which are the slopes of the asymptotes. These are shown in the figure as dotted lines 73 and 74.
  • the slopes of those lines are a direct measure of the energy of the radiation emanating from the source 51, and by means of ordinary calibration techniques well known in this art, the slopes can be correlated to specific energies. If a fluorescing specimen is the source 51, these energies are in turn then directly correlated to specific K-radiations of elements in the periodic table. The latter information, of course, identifies the elements producing the radiation at the source 51.
  • the above method is characterized by its simplicity and the rapidity with which the identification can be made. It is not adapted for providing information concerning the proportions of the different elements in an unknown specimen, but it will quickly identify those elements.
  • the techniques normally employed in utilizing the electrical information obtained in the systems illustrated in Figs. 1 and 4 are well known in this art of X-ray fluorescence spectrometry. It will be realized that the electrical information does not give an absolute indication, for instance, of the proportions of the elements in .512 the specimen. On the contrary, some 'form of calibration will be necessary. In its simplest form, the calibration will involve a comparison technique of the information obtained with the unknown specimen to the information obtained under identical conditions with a series of known specimens prepared in the same manner.
  • helium is the preferred gas
  • the other gases listed hereinbefore are also suitable to produce the results desired of the invention.
  • hydrogen would be, from a radiation transmitting and absorbing standpoint, as convenient as helium; however, its chief drawback would be its potential explosiveness; thus extreme care would be necessary to handle same.
  • the neon or nitrogen may be preferred, particularly where the gas can be utilized for its absorption edge to sharpen the separation of the wavelengths on opposite sides thereof.
  • the counters constituting the detection region can be operated either as Geiger-type counters or as proportional counters, and in certain cases even as ionization chambers.
  • the selection of a particular type of operation would depend upon the intensity of the radiation involved and the gas employed in the system. It will be appreciated that the Geiger-type of action provides the greatest amount of gas amplification and thus the largest amplitude signals in the output circuit.
  • the proportional-counter-type of operation has the advantage of producing pulses whose amplitudes are energy dependent.
  • the means by which a particular type of operation may be obtained is well known to those skilled in this art, and usually involves the application of a particular potential to the counter, which potential is dependent upon the gas pressure and the geometry of the counter. In the embodiment of Fig.
  • 1 and 4 is also not essential to the invention, it being also possible to employ plate-like cathode and anode electrodes, or constructions employing a plurality of anodes and a plurality of cathodes, or, finally, in the general geometry illustrated in the figures, even a cathode which is not cylindrical in shape but, say, rectangular, or even spherical.
  • the source of potential 27 has been shown with an arrow therethrough to indicate adjustability. This may be necessary for the following reasons. In operating this system, the pressure of the helium within the enclosure will be varied so as to optimize the sensitivity of the detection region to a particular radiation. However, it may be found that a potential suitable for providing counting action in the detection region at atmospheric pressure may be far too high for the potential suitable for providing counting action at, say 5 of an atmosphere. For this reason, it may be necessary to adjust the potential applied to the counter for each different pressure employed within the enclosure, which can be effected automatically by coupling said potential source 27 to the pressure control means 31. As has been explained in connection with the operation of the system in Fig.
  • the system and the method of the invention provide, for the first time known to us, a system for analyzing by means of gas detection the X-rays emitted by specimens containing unknown elements in the second period of the periodic table.
  • the applications of an instrument constructed along the lines indicated are truly immense. It will make available to the art for the first time means by which a non-destructive analysis of an organic specimen may be made in a relatively rapid and simple manner, thereby avoiding the use of extremely cumbersome, time-consuming and expensive wet chemical methods.
  • X-ray apparatus comprising an enclosure, means within said enclosure to generate ultra-soft X-radiation, means within said enclosure to transmit the X-radiation in a given direction, means within said enclosure positioned to intercept and detect said X-radiation, and an ionizable medium contained within and filling said enclosure,.said detection means comprising a pair of spaced electrodes defining a region in which said X-radiation is absorbed by said ionizable medium thereby generating electrical pulses.
  • X-ray apparatus comprising an enclosure, means Within said enclosure to generate ultra-soft Xradiation, means within said enclosure to transmit the X-radiation in a given direction, means within said enclosure posi tioned to intercept and detect said X-radiation, an ionizable gase contained Within and filling said enclosure, said detection means comprising a pair of spaced electrodes defining a region in which said X-radiation is absorbed by said ionizable gas thereby generating electrical pulses, and means to adjust the pressure of the gas within said enclosure to a value at which the sensitivity of said detection means is a maximum.
  • X-ray apparatus comprising an enclosure, means within said enclosure to generate ultra-soft X-radiation, means within said enclosure to transmit the X radiation in a given direction, means within said enclosure positioned to intercept and detect said X-radiation, an ionizable gas contained within and filling said enclosure, said detection means comprising a pair of spaced electrodes defining a region of given length in which said X-radiation is absorbed by said ionizable gas thereby generating electrical pulses, and means to adjust the pressure of the gas within said enclosure to a value at which the product thereof and said length is between about 0.01 and 400.
  • X-ray apparatus comprising an enclosure, means within said enclosure to generate ultra-soft X-radiation, means within said enclosure to transmit the X-radiation in a given direction, means within said enclosure positioned to intercept and detect said X-radiation, an ionizable gas contained within and filling said enclosure, said 14 detection means comprising a pair of spaced electrodes def ning a region in which said X-radiation is absorbed by said ionizable gas thereby generating electrical pulses, and means to adjust the pressure of said gasto a'value between about 0.01 and 2 atmospheres.
  • X-ray'apparatus comprising an enclosure, means within said enclosure to generate ultra-soft X-radiation, means within said enclosure to transmit .the X-radiation in a given direction, means within said enclosure positioned to intercept and detect said X-radiation, an ionizable gas contained Within and filling said enclosure, said detection means comprising a pair of spaced electrodes defining a region in which said X-radiation is absorbed by said ionizable gas thereby generating electrical pulses, means to adjust the pressure of the gas to a value at which a maximum portion of said X-radiation is absorbed in said detection region, and means to apply a potential to said electrodes.
  • X-ray apparatus comprising an enclosure, means within said enclosure to generate ultra-soft X-radiation, means within said enclosure to transmit the X-radiation in a given direction, means within said enclosure positioned to intercept and detect said X-radiation, and an ionizable gas having a linear absorption ooeflicient not greater than that of neon contained within and filling said enclosure, said detection means comprising a pair of spaced electrodes defining a region in which said X-radiation is absorbed by said ionizable gas thereby generating electrical pulses, and means to adjust the gas pressure within said enclosure to a value at which a maximum of said X-radiation is absorbed in said detecting region.
  • X-ray apparatus comprising an enclosure, means Within said enclosure to generate ultra-soft X-radiation, said means comprising a specimen adapted to generate ultra-soft X-radiation upon exposure to X-radiation con taining wave-lengths adapted to excite at least one element in said specimen to generate characteristic X-radiation, means within said enclosure to transmit the ultrasoft X-radiation in a given direction, means within said enclosure positioned to intercept and detect said ultrasoft X-radiation, an ionizable gas having a linear absorption coefficient not greater than that of neon contained within and filling said enclosure, said detection means comprising a pair of spaced electrodes defining a region in which said ultra-soft X-radiation is absorbed by said ionizable gas thereby generating electrical pulses, and means to adjust the gas pressure within said enclosure to a value at which a maximum of said ultra-soft X-radiation is absorbed in said detection region.
  • X-ray apparatus comprising an enclosure, means within said enclosure to generate ultra-soft X-radiation, means within said enclosure to transmit the X-radiation in a given direction, means within said enclosure positioned to intercept and detect said X-radiation, an ionizable gas consisting of helium contained within and filling said enclosure, said detection means comprising a pair of spaced electrodes defining a region in which said X-radiation is absorbed by said ionizable gas thereby generating electrical pulses, and means to adjust the value of the gas pressure to a value at which a maximum amount of X-radiation is absorbed in said detection region.
  • X-ray apparatus comprising an enclosure, means within said enclosure to generate ultra-soft X-radiation having a plurality of wave-lengths, means within said enclosure to transmit the X-radiation in a given direction, means within said enclosure positioned to intercept and detect said X-radiation, an ionizable gas contained within and filling said enclosure, said detection means comprising a pair of spaced electrodes defining a region'in which said X-radiation is absorbed by said ionizable gas thereby generating electrical pulses, and means to adjust the gas pressure within said enclosure to a value at which a maximum amount of X-radiation at one wave-length only is absorbed in said detection region.
  • X-ray apparatus comprising an enclosure, means within said enclosure to generate ultra-soft X-radiation nate against unwanted wave-lengths, and means to adjust having a plurality of wave-lengths, means within said enthe length of said absorbing region to further discriminate closure to transmit the X-radiation in a given direction, against unwanted wave-lengths.
  • said detection means comprising a pair of spaced electrodes defining a region of given UNITED STATES PATENTS length in which said X-radiation is absorbed by said 2,516,672 Brockman July 25, 1950 ionizable gas thereby generating electrical pulses, means 2,602,142 Meloy July 1, 1952 to adjust the gas pressure within said housing to discrimi- 10 2,683,220 Gross July 6, 1954 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 2,924,715 February 9, 1960 Charles F. Hendee et al. It is hereby certified that error appears in the of the above numbered patent requiring correction and that the said Letters Patentjshould read as corrected below.

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Cited By (18)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3042801A (en) * 1959-12-30 1962-07-03 United States Steel Corp Apparatus for analyzing a sample of material
US3052795A (en) * 1959-03-27 1962-09-04 Perkin Elmer Corp Radiation dispersion system
US3073952A (en) * 1956-09-11 1963-01-15 Gen Electric X-ray diffraction apparatus
US3084255A (en) * 1958-11-13 1963-04-02 Lab For Electronics Inc Radiation sensitive system
US3086116A (en) * 1959-03-24 1963-04-16 Sylvania Electric Prod Apparatus for determining radioactive material ratios
US3100263A (en) * 1962-02-21 1963-08-06 John W Verba Continuous rotation scattering chamber
US3105902A (en) * 1960-09-19 1963-10-01 Standard Oil Co Controlled atmosphere X-ray diffraction spectrometer
US3126479A (en) * 1962-03-01 1964-03-24 X-ray analyzer system with ionization
US3153144A (en) * 1961-02-03 1964-10-13 Applied Res Lab Inc Position adjustment mechanism and X-ray spectrometer including it
US3226550A (en) * 1962-04-19 1965-12-28 Philips Corp Gas-filled radiation detector with controlled density of gas filling
US3370167A (en) * 1964-07-13 1968-02-20 American Mach & Foundry Proton-excited soft x-ray analyzer having a rotatable target for selectively directing the x-rays to different detectors
US3471694A (en) * 1965-03-01 1969-10-07 Philips Electronics & Pharm In Charge particle barrier consisting of magnetic means for removing electrons from an x-ray beam
US3678274A (en) * 1969-10-29 1972-07-18 President Of Tokyo Univ Diaphragm-less radioactive radiation counter
US3852596A (en) * 1970-03-20 1974-12-03 Philips Corp Cold cathode gaseous discharge device for producing electrons in an x-ray fluorescence analysis apparatus
FR2501379A1 (fr) * 1981-01-08 1982-09-10 Le N Proizv Spectrometre fluorescent a rayons x
US4959848A (en) * 1987-12-16 1990-09-25 Axic Inc. Apparatus for the measurement of the thickness and concentration of elements in thin films by means of X-ray analysis
US20090116613A1 (en) * 2006-04-11 2009-05-07 Rigaku Industrial Corporation X-ray fluorescence spectrometer
CN105074441A (zh) * 2013-02-28 2015-11-18 一般社团法人矿物研究会 生物体内元素检查方法

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE1288341B (de) * 1960-03-12 1969-01-30 Well Completions Inc Verfahren und Vorrichtung zum Nachweis von chemischen Elementen in einer aus koernigen Bestandteilen bestehenden Probe
DE1223569B (de) * 1960-09-08 1966-08-25 Commissariat Energie Atomique Vorrichtung zur Schichtdickenbestimmung durch beta-Bestrahlung und Messung der rueckgestreuten charakteristischen Roentgenstrahlung

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US2516672A (en) * 1944-05-27 1950-07-25 Socony Vacuum Oil Co Inc Apparatus for measuring radiant energy
US2602142A (en) * 1949-11-15 1952-07-01 Melpar Inc X-ray spectrograph
US2683220A (en) * 1949-06-04 1954-07-06 Gen Aniline & Film Corp Spectrograph device

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2516672A (en) * 1944-05-27 1950-07-25 Socony Vacuum Oil Co Inc Apparatus for measuring radiant energy
US2683220A (en) * 1949-06-04 1954-07-06 Gen Aniline & Film Corp Spectrograph device
US2602142A (en) * 1949-11-15 1952-07-01 Melpar Inc X-ray spectrograph

Cited By (19)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3073952A (en) * 1956-09-11 1963-01-15 Gen Electric X-ray diffraction apparatus
US3084255A (en) * 1958-11-13 1963-04-02 Lab For Electronics Inc Radiation sensitive system
US3086116A (en) * 1959-03-24 1963-04-16 Sylvania Electric Prod Apparatus for determining radioactive material ratios
US3052795A (en) * 1959-03-27 1962-09-04 Perkin Elmer Corp Radiation dispersion system
US3042801A (en) * 1959-12-30 1962-07-03 United States Steel Corp Apparatus for analyzing a sample of material
US3105902A (en) * 1960-09-19 1963-10-01 Standard Oil Co Controlled atmosphere X-ray diffraction spectrometer
US3153144A (en) * 1961-02-03 1964-10-13 Applied Res Lab Inc Position adjustment mechanism and X-ray spectrometer including it
US3100263A (en) * 1962-02-21 1963-08-06 John W Verba Continuous rotation scattering chamber
US3126479A (en) * 1962-03-01 1964-03-24 X-ray analyzer system with ionization
US3226550A (en) * 1962-04-19 1965-12-28 Philips Corp Gas-filled radiation detector with controlled density of gas filling
US3370167A (en) * 1964-07-13 1968-02-20 American Mach & Foundry Proton-excited soft x-ray analyzer having a rotatable target for selectively directing the x-rays to different detectors
US3471694A (en) * 1965-03-01 1969-10-07 Philips Electronics & Pharm In Charge particle barrier consisting of magnetic means for removing electrons from an x-ray beam
US3678274A (en) * 1969-10-29 1972-07-18 President Of Tokyo Univ Diaphragm-less radioactive radiation counter
US3852596A (en) * 1970-03-20 1974-12-03 Philips Corp Cold cathode gaseous discharge device for producing electrons in an x-ray fluorescence analysis apparatus
FR2501379A1 (fr) * 1981-01-08 1982-09-10 Le N Proizv Spectrometre fluorescent a rayons x
US4959848A (en) * 1987-12-16 1990-09-25 Axic Inc. Apparatus for the measurement of the thickness and concentration of elements in thin films by means of X-ray analysis
US20090116613A1 (en) * 2006-04-11 2009-05-07 Rigaku Industrial Corporation X-ray fluorescence spectrometer
US7949093B2 (en) * 2006-04-11 2011-05-24 Rigaku Industrial Corporation X-ray fluorescence spectrometer
CN105074441A (zh) * 2013-02-28 2015-11-18 一般社团法人矿物研究会 生物体内元素检查方法

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NL217744A (enrdf_load_stackoverflow)
FR1176408A (fr) 1959-04-10

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