US2635192A - Fluorescent spectral analysis - Google Patents

Description

April 14, 1953 FLUORESCENT Filed 001,. 24, 1949 M. A. CORDOVI 2,635,192

SPECTRAL ANALYSIS 5 Sheets-Sheet l 1%1-53 30 SLIDE SCAN (D F I 6. I

INVENTOR fl ggrcel A. Cordow ATTORNEY April 14, 1953 M. A. CORDOVI FLUORESCENT SPECTRAL ANALYSIS 5 Sheets-Sheet 2 Filed 001,. 24, 1949 96 FIG. 2

INVENTOR Marcel A. Cordow ATTORNEY 5 Sheets-Sheet 5 Cir -4 INVENTOR Marcel ,4 Cordovz D' aM/ ATTORNEY M A CORDOVI FLUORESCENT SPECTRAL ANALYSIS CC'W-3 I I can 4 I I cow-2 Lq, l

FIG.5

April 14, 1953 Filed Oct 24 1949 A ril 14, 1953 M. A. CORDOVI 2,635,192

' FLUORESCENT SPECTRAL ANALYSIS Filed Oct. 24, 1949 5 SheetsSheet 4 PERCENT /RON PERCENT N/CKEI. 1

PERCENT CHROM/UM ANGLE 0F REFLECTION FROM ROCKSALT (2 MENTOR F I G. 6 Marc?! A. Cardow Wmwu ATTORNEY April 1953 M. A. CORDOVI 2,635,192

FLUORESCENT SPECTRAL ANALYSIS Filed Oct. 24, 1949 5 Sheets-$heet 5 Q". I 37 l Jfil J 37 3a BET 38 1 706 2/ 20 9 /06 FIG. 8 40 INVENTOR Mc cce/ A. Coraow' Patented Apr. 14, 1953 FLUORESCENT SPECTRAL ANALYSIS Marcel A. Cordovi, Forest Hills, N. Y., assignor, by mesne assignments, to The Babcoek & Wilcox Company, Jersey City, N. J., a. corporation of New Jersey Application October 24, 1949, Serial No. 123,165

15 Claims.

This invention relates to the quantitative and qualitative analysis of chemical elements and compounds, such as metals, alloys, minerals, ores, liquids, etc., with respect to their elemental constituents and, more particularly, to an improved crystal spectrometer for analyzing the fluorescence spectra of such elements or compounds when bombarded, for example, by X-rays.

The theory of fluorescence analysis is based upon elementary concepts associated with radiation spectra. When a material is bombarded by cathode rays, the resulting X-ray emission consists of a general or continuous (white) spectrum and a superposed characteristic ray spectrum extending over a range of wavelengths from about to 10 centimeters. The continuous spectrum is independent of the target material and its general features preclude the possibility of directly associating it With its emission source. The monochromatic rays of the characteristic X-radiation, however, are grouped in simple series, with wavelengths depending upon the atomic number of the emitting element.

Emission of characteristic X-rays is due to the inner electrons of the atom. According to Bohrs theory, these electrons are supposed to occupy shells, designated as L, M, etc., around a central nucleus and to whirl around it in the same way that the planets revolve about the sun. Thus, when an impinging electron collides with an atom of the target and ejects one of its electrons, say from the innermost (K) orbit, the vacancy is filled instantly by an electron from the outer shells (L, M, etc). As a result, a line of the K series will be emitted, its energy value depending on the source of the replacement electron.

Wave lengths of the spectral lines comprising the K, L, M etc. series are inversely proportional to the square of the atomic number. In other words, the higher the atomic number of the target material, the shorter the wavelength of radiation and the greater its penetrative power. The K emission lines represent the shortest wave length group and. are the most important of the various series in view of their comparative simplicity and high intensity. The K series of all elements, except the lightest, consists of four principal lines, of which the 111112 doublet is the most intense and closely spaced. By comparison, the L series spectrum is more complex in View of the numerous lines (about thirty have been identified) of much lesser intensity than the K series.

Chemical analysis by X-rays is made DOSSlDl-u by the specific and distinguishing features of characteristic rays for each element in the target and by the direct, though not necessarily linear, relationship existing between the percentage of these elements and the intensities of their emission lines. These conditions will be satisfied also if a sample is irradiated outside the X-ray tube, provided the primary radiation is of sufliciently short wave length and the X-ray quanta have energies nearly approaching those of the electrons in the cathode beam. The fluorescence spectra, i. e. the line radiation resulting from the excitation of an atom by the absorption of X-rays, can be then conveniently identified with a crystal spectrometer. Secondary fluorescence spectra are of much lower intensity as compared to direct excitation. This is so because, when a sample is irradiated outside the X-ray tube, the intensity of exciting radiation per unit area falls cit with the inverse square of the distance from the focal spot. This drawback, however, is largely overshadowed by several important advantages pertaining to the secondary fluorescence spectrum which make it the most practical source of radiation for chemical identification purposes.

There is now available to the art a fluorescence analyzer for use in quantitative analysis of elemental constituents in metals, minerals, and ores. Some of the outstanding features claimed for this analyzer are that (1) determinations may be made either on an absolute basis or a comparative basis on percentages up to 100%, with a reproducibility to better than 5%; (2) the unit does not require exceptional stabilization of line potential; (3) determinations are independent of phase or structure; and (4) the analyses are speedy and the unit does not require specialized technical training for operation.

Experimental work undertaken to evaluate this analyzer, from an industrial viewpoint for routine chemical analyses of metallic materials, indicates that the above claims are not substantiated. For example, in out of tests, re-

producibility oi results was only between 6% and 20%, or from 1% to 15% outside the claimed accuracy range for comparative analyses, and would be even further outside the claimed range if analyses were attempted on an absolute basis. In the latter case, furthermore, exceptional tech nical skill and tedious procedures become mandatory for evaluation of many correction factors such as crystal reflectivity, counter or detector sensitivity, mutual excitation and Iinanneren unhhewn ea hpleiseuhiee ten ,.ehert r e ehe h rima y rad at onem 7 absorption of component elements of the specimen, air absorption, and proportionality factors.

I have found further that the present commercial analyzer cannot be usefully employed for routine analyses of metals and alloys without e pt o a st bil y of the l ne ne eh ie-i- In h .iree h a a se r hein l teehne logical requirement stipulates an accuracy and reproducibility of results to better than 11%, and this is possible only with special equipment assuring the highest degree of voltage stabilization.

. I have also found that, contrary to the above claims, determinations are dependent up the structure and predominant phase of the specimen, and comparative analyses cannot be made tween samples which are chemically si.

more than one major constituent but W 11 f} structure or predominant phase. For ex nple,

a east eneeihe h eehnet e helytieei r eehiner wi h a wr ugh e 931 1 1; though eh miee l sim lar he eeinm e than the meiei'eehstitu it eel he an rt e i 0th s me and e he fi i ncies 9 the trie art ar el min t d, the invent eh ana yzer be n e rie: eia lav ad p d to: eut ne er d iet ohehe teeeei irentst l nd therth tellieinet riele- In e e te efler a be ter un rstandin f the under ng Pr n iples e he invent 1e h iet eleeeri ti n of theee retiehei preeeeiur wi h th mentioned prior art analyzer will be oi assist:- anc This ana yze e erates the iehew s to in,

tungsten aft-ra Iiiheeeee siery 8313995128 a th s mple a e H 7,, el imatoe fii i fill to strike eerretal l zee- The etter actin s e e treetieh eretiha separates the eehie ne t e iati ns h ii] A pro e pesi io hs. refle ts hem at a the s er stic Brag a g l iv duele ente of the ation are deteeted by Gag-enco nter. transmits he m ulses recei ed to an electr ni in and cou n uhit- .(iennts a e t tehzei er a defin P ed of me a d the ercenta e of he elemen unde in est ation is h h iiby p epertio i s with simi ar dat obtainedimm a samp e f known eleme tal content- A h gh o ta e ne at r is nee to ergiz the 'X- a u e. Wh eh has etilhsste tars tsealed ofi by a beryllium window. The specimen is irradiated ou e he X-ray tub (5. le el; nd is o t si a 4.5 de rees to the axis or the eene o i eid ti -r -ye- The s mple is simila ly p t ned h e p ct to th ee imator. wh c consists of a .hen y e he thi all n c tub,-

re ter; Z-ihch we nch. t-i eh e lt-iheh ons) packed into an al minumireme J of etensu ar ereseee enelhhletei ie a y 1 4 serves to transmit a nearly parallel beam of fluorescence radiation to the crystal analyzer, which is usually rock salt or calcium fluorite.

The NaCl crystal is satisfactory for the K series of the elements ranging from about titanium (Ka1=2.74=631 A. U.) to zirconium (Ka1=0.78851 A- U 1 spectra of elements above atomic num er e dee ee in inten i in. prop to the sine of the Bragg angle. To compensate for the diminishing dispersion in the spectra of such elements, it is necessary to use crystal planes with smaller grating constant. This requirement is partially met by fluorite, whose atomic plane ing; (@213) plane, is 1.93 A. U. as compared to a U: iet teehe plane- With this flugz escence analysis unit, it is possible to analyze that group of elements Whose atomic number falls between about 22 and 50. The limited peak voltage (-50 kilovolts) in the primary X-ray spectrum is insufiicient to excite etheiehti the eeeetree1 lement with high etemie huieh Qe t e her the were len hs. e the li hter elemen s teete ite 'iehe htereet 9 The lem nts. ehev e hiie winter it e. anal ze b thei h e iesii ee. eihs ex ende eventing i r a s t eemee ete er the 992 .1- paratively low intensities of these spectra (LalIKqlZlQL '7 h The tu is elm e it eeheet meta i e n o wh h t e i hi ter e tend t ese el me s eing so a an ed tet h t e 9f the en e e y -i' rs end e i i im er nd a t heep-ee ihen- I e ter is me dih e ret e ht e ih t ne eltiet ns d e'h f u e ee mehei eheei there a w h m y h ve eithewh ease/sis e e hi i n h t e t e ee eiiheh Q1. e s ehderv .reele ei' e ,fie eeeeht teen. when exposed to n ihei eh ei (specimen) which is exposed to the incidentc of X-rays. The intensity of radiati is also. fluenced by the geometrical anemggamtr the emp and e tete- Oet e'tes e ofth e considerations, the specimen holderofthe analyzer is not only impractical but also is n r to analytical errors. Its imprati'atm irg p the tedious, hence'cost yfinacljning' f spec'il. ti he t0 he ifie iiie h ie in at e et en ih'i he e e h e teki ei ee e l im e. he leees eht t h i' h ee a a er for the specimen, may be easily deformed b he pressureexerted upon it While inserting thick specimens in the holder. Resulting variation in the set position of the samples with respect to the X-ray tube, will produce changes in intensity which become criticalespe cially' in fthecase of elements Whichare present in residual amounts. Another difiicultyencountered inth-e practical operation of the unit results during changingoi the specimens in the holder. During these 10;)- erations, the housing must be e ene' tdtiiow access to the specimen holder." Consequently, to prevent hazardous exposure of operatingpersonnel to X-rays, it is necessary to'd-eeneligize the X-ray tube while the housing is openl Even though such deenergization may beof" a very small duration, such as a few seconds for example, the restarting of the I i-ray tube takes up to ten pr more times the duration of the interruption to reach a stabilized gondition. Thi seriouslyidelays the analytical procedure.

To overcome the foregoing defects in the specimen holder and to eliminate such delays in the analytical procedure, one feature of the present invention is the provision of an improved specimen holder. This improved specimen holder comprises a fiat slide reciprocable longitudinally of the external surface of an apertured wall of the X-ray tube housing. The wall aperture is arranged substantially at the intersection of the X-ray cone axis with the central plane of the collimator and has chamfered walls so as not to block any radiation. On its inner surface, the slide has a lining of lead, and means are provided to hold the slide firmly against such wall with the lead lining in smooth surface-to-surface jux taposition therewith.

The front or outer face of the slide has two or more longitudinally spaced recesses in which specimens may be held by suitable clamping means. At substantially the center of each recess, a hole is formed through the slide, these holes being selectively alignable with and forming a continuation of the X-ray housing aperture by longitudinal movement of the slide. The slide may be manually operated, but preferably is motor driven under the control of indexing push buttons. Thereby, to align a selected specimen with the housing aperture, the operator presses the proper push button and the motor automatically indexes the slide to the correct position for such specimen. A relatively large lead shield is hingedly mounted on the housing cover and. when the apparatus is in operation, is suspended therefrom in covering relation to the portion of the slide adjacent the housing aperture.

The invention specimen holder permits a rapid succession of analyses to be made without deactivating the X-ray tube. During movement of the holder from one indexed position to another, the housing aperture is sealed by the lead lining on the inner surface of the slide, preventing exit of X-radiation from such aperture. The specimens are quickly and easily positoned in the recesses from the front of the slide, when the recesses are out of alignment with the aperture and either side of the external movable lead shield or cover. For any extended break in analysis, an externally controlled lead curtain or shield, movably mounted within the housing, may be moved to a position blocking the window of the X-ray tube to cooperate with the external shield in blocking exit of radiation.

As stated above, the unknown and the standard specimens being compared must be closely representative of each other with respect to metal.- lurgical phases, major constituents, structural conditions, and surface preparation. In most industrial analyses, this does not present any diffculty, as the approximate analysis of the sample being analyzed is known, and it is merely necessary to use a similar standard. However, with a sample whose approximate analysis is unknown, it is necessary first to establish its identity qualitatively and, after the elemental constituents have been identified, to then run a quantita tive comparison analysis with a similar standard specimen.

A feature of the invention is the provision for making a simultaneously recorded quantitative and qualitative analysis rapidly and automati cally, For this purpose, a synchronous motor is used to drive the crystal mounting arm over the goniometer scale through the area to be analyze A synchronous motor driven recording instrument, such as a recording potentiometer, is con- 6 nected to the frequency meter circuit of the analyzer. With the recorder and the goniometer initially synchronized, the recorded quantitative and qualitative analysis can be carried out without manual attention.

The analysis is depicted by a graph line on the recorder chart. Provided a properly calibrated chart is utilized, the quantitative analysis can be made on an absolute basis, 1. e. without the use of a standard specimen for comparison analyses. This requires a difierently calibrated chart for the different types of alloys or compositions being analyzed. For example, the calibration of the percentage scale for chromium in straight chromium (ferritic) steels would diiier from the calibration of the percentage scale for chromium in chromium-nickel (austenitic) steels. The calibrated charts may take any one of several forms. If quantitative analyses are being made solely for chromium, charts may be used which have a plurality of chromium percentage scales each calibrated for the chromium percentages in different types of chromium bearing alloys. On the other hand, if quantitative and qualitative analyses are being made for all the elemental constituents of selected specimens, the charts used will have calibrated percentage scales for all elements, such as iron, nickel, chromium, etc., of a particular type of alloy, charts having differently calibrated percentage scales being used for each different type of alloy. To determine the particular type of alloy to which an unknown specimen is germane, a rapid, qualitative and relatively quantitative analysis can be made before the final quantitative analysis.

The elemental analysis to classify an unknown specimen may be greatly facilitated by the use of standard charts for comparison with the recorded chart produced by the elemental analysis. For example, with standard charts prepared for 18-8, 25-20, and other alloys, a comparison of the standard charts with the recorded chart will provide an indication of the relative chart peaks and their relative locations. Thus, the magnitudes of the similarly located peaks may be com-- pared to obtain an approximation of the relative intensities of radiation, thereby classifying the specimen as to type.

To facilitate these analyses, a push button control of the scanning operation is provided. Additionally, the specimen holder may be motor operated between its analyzing positions under the control of push buttons and limit switches.

Experimental analyses have further shown that an analyzer arrangement involving angles of 45 between the sample and the axis of the incident cone of X-ray and between the collimator and the sample, thus providing an included angle of between the X-ray cone axis and the collimator, is not always the best angular arrangement for optimum results. For instance, incident angles, other than 45, in the range from 30 to 60 produce better results with certain elements. Accordingly, the invention analyzer is capable of adjustment of the angular relationships.

For accurate reproducibility of results, it is essential to constantly maintain a uniform atmosphere for the passage of the radiation from the specimen through the collimator and past the analyzer to the radiation detector. The aforementioned air absorption may be reduced by using an inert gas, such as helium, for the uniform a"- mosphere, or the system may be evacuated. For this purpose, the invention analyzer includes a gas-tight housing for the X-ray tube, into which the collimator extends in sealed relation, and a flexible gas-tight hood interconnecting the radiation detector and the outer endof the collimator and enclosing. the crystal analyzer. The enclosed system may be connected to a suitable source of an inert gas or may be connected to a vacuum pump, as may be necessary or desirable during a particular analysis.

In ananalyzer adapted for routine production analysesof metallic materials, the. protection and mounting of the crystal analyzer are important in securing uniform results and in facilitating the analyses. To prevent any change in the, reflectivity properties of the crystal analyzer, such as due tov hygroscopic action, the crystal analyzer is coated with an extremely thin coating of. a pro.- tective material, such as liquid envelope. r example, which Weatherproofs the surface of the crystal analyzer without aife'cting the characteristics of the crystal analyzer. Also, in setting up the apparatus, the crystal analyzer must be carefully adjusted both angularly and otherwise, to obtain the optimum reflecting relation to. the radiation detector. This initial adjustmentmust be carefully made. and requires, a considerable amount of time. If the crystal analyzer is replaced, the time consuming initial adjustment must be performed again. To; eliminate this undesirable re-adjustment, the crystal holder of the invention analyzer is. provided with micrometer adjustments, whereby a record of the optimum settings for difierent crystals may be made and such settings rapidly reproduced.

With the foregoing in mind, it is an object of the invention to provide an improved X-ray type crystal spectrometer or analyzer for analysis of compositions utilizing fluorescent radiation therefrom and which is particularly eficient in the accurate analyses of metals and alloys.

Another object is to provide such an analyzer having an improved specimen holder capable of providing more accurate and speedier analytical results.

A further object is to provide such an analyzer in which a suitable gas or evacuation is employed as a means of providing a uniform atmosphere, other than air, thereby eliminating absorption of radiation.

Yet another object is to provide such an analyzer including automatic specimen holder positioning means and automatic scanning means.

Still a further object is to provide such an analyzer including means for making direct quantitative analyses of the elemental constituents of unknown compositions of known types.

An additional object is to provide such an analyzer in which. it is not necessary to interrupt the X-ray tube energization between analyses.

Another and additional object is to provide a fluorescence spectra analyzer with which a quantitative analysis of an unknown specimen may be made by simultaneously analyzing the unknown specimen and a comparison or standard specimen of the same type as the unknown and charting the differential intensities of radiation at common characteristic Bragg angles.

These and other objects, advantages and novel features of the invention will be apparent from the following description and the accompanying drawings. In the drawings:

Fig. 1 is a plan view of a fluorescence analyzer in accordance with the present invention, the drive for the specimen holder being omitted to simplify the illustration;

8 Fig. 2 is an elevation view of the analyzer, showing improved specimen holder and its drive;

Fig. 3 is an end elevation view of the specimen holder and a portion of the X-ray tube housing;

Fig. 4 is. a schematic wiring diagram of the tively analyze a known and an unknown speci men, and record the difierential intensities of radiations at common characteristic Bra angles;

Fig. 8 is a partial schematic plan view, corresponding to Fig. 7, but using a single X-raytube; and

Fig. 9 is a partial schematic elevation viewof the X-ray tube and specimen of Fig. 8.

Referring more par icularlyto' Figs. 1-, 2,- and 3 of the drawings, the analyzer ill includes a base plate i, of aluminum, steel, or any desired: material, on which is mounted a housing id, of suitable metal, having a removable cover It. In plan, housing 5 and its cover l2 may, for examplabe triangles, with the vertex angle being opposite the longer forward wall is which extends beyond the other walls M, it of the housing at either end. The interior of housing is is lead lined, as indicated at H, and cover 12 has lead-lining it on its under surface.

Within housing t5, adjacent wall it and substantially midway of the latter, is mounted an X-ray tube having water cooling connections as indicated at 25, 22. The axis of the X=ray cone, inv the angular relations shown in Fig. 1-, is directed at 45 to wall it and intersects. the collimator cone axis substantially at the outer surface of wall is and at the center of aperture 25. Collimator comprises a honeycomb of thin walled nickel tubing packed into an elongated, rectangular aluminum frame. Alternatively, the frame may be transversely subdivided by closely spaced, parallel longitudinal partitions to form a plurality of elongated slits extending through the frame. Within housing i5, collimator 30 carries a pair of brackets 2 3, 24 which slidably support a rod 26 extending through wall l land having an operating handle 2'! on its outer end. On its inner end, rod 26 supports a lead shield or curtain 28 for longitudinal movement into and out of a position intercepting X-rays directed from tube 29 toward aperture 25 and essentially blocking the X-ray tube Window.

It has been found that maximum excitation of the characteristic spectra of certain elements is obtained when the element is bombarded by a primary X-ray beam at angles smaller or larger than but usually lying between 80 and For this reason, tube 25 is mounted for adjustment along an arcuate track is having its center at the intersection of the X-ray cone axis and the collimator axis.

The X-rays from tube 28 directed through aperture 25 impinge, at the selected angle, upon a specimen mounted. in a manner to be described, in flush relation with the outer surface of wall 3. The resultant secondary fluorescent spectra from the irradiated specimen are directed through the" collimator 5G and allowed to strike acrystal analyzer 35. The latter acts, as previously stated,

as' a diffraction grating to separate the component spectra and, by proper positioning, to reflect them at a characteristic Bragg angle. The individual quanta of radiation are detected by a Geiger counter 40 which transmits the received impulses to an electronic scaling and counting unit 45 (Fig. 6).

For this purpose, and in accordance with the present invention, crystal analyzer 35 and Geiger counter 40 are mounted on a -90 goniometer 58 having one fixed radial arm 3! aligned with collimator 30 and another fixed radial arm 32 perpendicular thereto, the outer ends of the fixed arms being interconnected by a quadrant 33 having arcuate racks 34 and 33 along its radially inner and outer edges, respectively, and being graduated from 0 to 90. Crystal analyzer 35 is mounted on the inner end of a movable radial arm 31 pivoted at the axis of goniometer 53, and Geiger counter 40 is mounted on another movable radial arm 38 likewise pivoted at the goniometer axis.

In the operation of the apparatus so far described, arms 31 and 38 are angularly adjusted along quadrant 33 to change the angle of crystal analyzer 35 relative to collimator 3B and the angle of Geiger counter as relative to analyzer 35. During such adjustment, the angle between arm 3! and arm 3| is substantially one-half the angle between arm 38 and arm 3i, with a tolerance of several degrees of the secondary arm 31. In other words the angle between the axes of Geiger counter 40 and collimator 3a is always substantially twice the angle between the plane of crystal analyzer 35 and the collimator axis. The characteristic Bragg angle for any particular element is the angle between arms 31 and 38 when the spectra due to such elements are at a maximum intensity as indicated by Geiger counter at and counting and scaling unit 45. The foregoing angular relations of the collimator, crystal analyzer, and Geiger counter are known to the art.

In known fluorescent analyzers, arms 3?, 38 are manually adjusted over quadrant 33, a Vernier adjustment being provided on one or both arms. In the present invention, and as somewhat schematically indicated in Fig. l, a small reversible motor 4! is mounted on a bracket 42 on arms 3'! and includes a worm drive l3 arranged to drive a pinion 44 meshing with the outer rac 3c of quadrant 33. Similarly, a small reversible motor 45 on a bracket 41 on arm 38 has a worm reduction unit 48 driving a pinion 49 meshing with inner rack 3-1 of quadrant 33. To provide the described angular relation of arms 3! and 38, motor 4|, and its drive 43, 44, is arranged to operate arm 3! at substantially one-half the rate of operation of arm 38 by motor 46 and its drive 48, 49. The described driving arrangements form part of an automatic scanning system which will be described more fully in connection with the schematic wiring diagram of Fig. 5.

In order to assure accurate reproducibility of results, it is absolutely essential that a uniform atmosphere be constantly maintained between the irradiated specimen and the radiation detector. If an inert gas, such as helium, is introduced into the system, the air absorption of radiations may be reduced. Furthermore, evacuation of the system will eliminate radiation absorption by air. In either case, the system must be sealed between the specimen and the entrance to the Geiger counter.

The housing Hi can be made substantially air tight due to the compressibility of the lead linings ll, [8, or a sealing gasket can be used between the housing and its cover, and collimator 30 and rod 26 can be mounted in air tight relation through the wall I4, aperture 25 being sealed by the specimen holder and specimens, as will be described. A flexible, gas-tight sleeve 55, of rubber or similar material, interconnects the outer end of collimator 30 to the inner end of Geiger counter t0, being sealed to both of these elements and enclosing crystal analyzer 35. A connection 5| is provided on sleeve 55 and may be connected to a suitable source of an inert gas, or to a vacuum pump, dependent upon the desired conditions. Such connection may, of course, be located elsewherein the system, as at the housing I5.

It should be noted, at this point, that aperture 25 is suitably chamfered or bevelled so that there is substantially no obstruction to the X-rays entering the aperture and, more importantly, to the fluorescent spectra passing from the specimen to the collimator 30. Also, the illustrated arrangement of X-ray tube 29 and collimator 38 substantially decreases the distance between the tube and the specimen, as compared to prior arrangements in which the specimens were mounted in an indexing holder within the housing I5. For example, the X-ray tube is /8" closer the specimen than hitherto possible. As the intensity of secondary radiation is inversely proportional to the square of the distance between the X-ray tube and the sample, any decrease in such distance is very markedly effective in increasin the inten sities of the fluorescent spectra.

Another improvement is in the collimator; In known prior art analyzers, the collimator is packed with fa" diameter nickel tubing. By packing the collimator with s 2 nickel tubing, or by providing it with closely spaced, slit-forming separators of suitable thickness, the resolution of the spectra is greatly improved but at a small sacrifice in intensity. However, such reduction in intensity is more than compensated by the abovementioned decrease in the distance between the X-ray tube 20 and the specimen.

To weatherproof crystal analyzer 35, when the latter is hygroscopic, for example, the crystal analyzer is provided with a very thin film of a coating, such as the one known to the art as liquid envelope. This coating when properly applied, does not interfere with the diffraction grating action of the crystal analyzer.

The construction and mounting of the novel specimen holder 6|] will be best understood by reference to Figs. 1, 2, and 3. The upper section of wall l3 of housing I5 is reduced in thickness, by machining or the like, providing a shoulder 52. On the thicker wall portion below this shoulder are mounted a pair of rails 33, extending longitudinally of wall i3 and in vertically spaced relation to each other. Rails 53 are secured by bolts 54 to wall l3, and each rail has a longitudinally extending, semi-cylindrical groove 56 in one horizontal surface, the grooves opening in opposed vertical directions as seen in Fig. 3.

Specimen holder .60 includes a vertical panel 6| substantially aligned with shoulder 52. The rear surface of panel 6| has a longitudinal channel 62 therein containing a lead lining 63, channel 62 and its lining being aligned with aperture 25 and extending a substantial amount above and below the same. The forward face of panel 6i is formed with a pair of longitudinally spaced, vertically extending grooves 64, 64, the base of each having a chamfered hole 65, 65 each somewhat larger than aperture 25. When the correspondin groove is longitudinally centered with aperture 25 its hole 65 or B is aligned with the aperture. Holes 55, 65' extend through lead lining $3.

Grooves 6t, 5t receive the specimens l9, it, respectively, one of which may be an unknown and the other a standard, or vice versa. To hold the specimens against the bases of the grooves, bolts or studs 6%, 66 extend outwardly on each side of each groove. Each pair of bolts supports a bar El, 6? having a stud as, $8 centrally mounted therethrough and formed with a hardened point H, i l to engage a specimen. Nuts l2, 12 mounted on studs 55, 6t compress springs 59, 69 engaging bars 6'5, ti. When in position, specimens l e, lil rest on blocks l3. l3, respectively, set in the lower ends of grooves 6 3, st, and are held flush against the bases of the recesses by the pointed studs 63, $8.

Specimen holder 63 is supported for longitudinalsliding movement on tracks 53, 53 in the following manner. An elongated bar '53 has, in its upper surface, a semi-cylindrical groove i i complementing groove 56 of lower track 53, and groove 14 has secured therein plugs 76 retaining ball bearings engaged in groove A block ll has, in its'flo'wer surface, a semi-cylindrical groove is complementary to' groove 56 of upper track 53 and having secured therein plugs Si retaining ball bearings in upper groove 55. Bar l3 and block ll have vertical inner surfaces engaged with wall I 3. The outermost surface 82 of block I! is tapered for. cooperation with the tapered surface of a horizontally elongated wedge 33. Block El and wedge 33 cooperatively form a T-slot receiving an inverted T-bar 8 A vertical cover plate 85 is secured to the outer surfaces of bar 73 and wedge 83.

The vertical panel 3! is secured to a rectangular bar 8? which is adjustably secured to the stem of T-bar 84 by studs 88. As these studs are tightened, T-bar 84 is drawn toward bar 8?, but its upward movement is limited by the portion of the T-slot formed in block ii. A force is exerted downwardly on wedge 83 by bar 8?, in turn forcins T-bar 8t and bar 8'! inwardly toward wall is. Thisacts to force panel st, and particularly lead lining 63, tightly against the surface of wall 13. To protect against the X-rays passing through specimens 18,75, a lead shield it, of substantial extent, is hingedly mounted on cover 12 in alignment with aperture 25 so that it covers whichever specimen is aligned with the aperture.

Specimen holder to may be manually operated to selectively position specimens 7 8, to in front of aperture 25 for irradiation by X-ray tube 28. Preferably, however, the specimen holder is automatically selectively positioned under control of push buttons 8 and? (Fig. l) which may be conveniently mounted on plate I i. For this purpose, a nut 88 is secured to the inner surface of plate 86 and has a cylindrical bore receiving a reversely threaded screw 98 engaged by a pin 9! in' the bore of nut 80. As shaft 90 is continuously rotated in one direction, pin 93 travels alternately along each of the reversely directed threads to reciprocate holder til. Shaft 99 is rotated by a motor 95 through the medium of reduction gearing 9i serving to mount'one end of the shaft. The opposite shaft end is rotatably supported in a bearing bracket 92 on plate H.

The operation of the automatic holder positioning'system will be clear from Figs. 3 and 4. A limit switch operator 93 is secured to plate 86 and; is arranged to open either or a pair of nor,-

i2 mally closed limit switches 94, 98, one at each limit of travel of holder 60 and both connected in series with motor 95. Switches 94, 96 are so located as to open the circuit of motor -whenever one or the other of the specimens 7!}, 70' is" analysis position, operator 93v engages and opens switch 965 to stop movement of holder 60., Posh tioning of specimen it in the analysis position is. effected by pressing push button I shunting:

switch 536. Holder 59 may be stopped in any intermediate position by operating push button Bl which, while shown as a push button, may be an on-off snap switch.

The automatic positioning control arrange:-

ment of Fig. 4 is used in making analyses wherein an unknown specimen lei is compared with a known specimen iii having an analysis and PTO. duction history comparable to that of the un:

known specimen. Holder 5! is positioned at an.

intermediate location with lead lining 63 efiece tively sealing aperture 25 so that the X-ray tube may be activated to warm-up while theknown and unknown specimens are being clamped in holder 68. Rod 25 is preferably moved inward to position shield 28 in front of the X-raytubewindow to block X-rays from aperture 25.v The specimens are preferably prepared witha flat ground surface finished with emery paper. After the specimens have been positioned, shield 28 is withdrawn, lead shield l5 is lowered over the holder, switch 97 is closed, and push button I operated to position specimen It in front of aperture 25.

Specimen it is then analyzed by shifting arms 37, 38 over the quadrant 33, the counts from Geiger counter to being totaled over a mode: termined time interval at each characteristic Bragg angle position. This operation may be effected manually or specimen iii may be auto.- matically scanned, as will be described in con-.-

nection with Fig. 5. When analysis of specimen 753 is completed, push button 2 is operated to position unknown specimen it in front of aperture 25, and specimen iii is analyzed in the same manner. Comparison of the two analyses will provide a quantitative analysis of specimen 70' within the accepted limits of accuracy and re-. producibility of results. To insure such accuracy, a sensitive voltage stabilizer is included in the energizing circuit X-ray tube 29, asfthere' isadirect relation between intensity of fluorescence and the voltage across the X-ray tube. With the usual line potential fluctuations common in in dustrial plants, such X-ray tube voltage stabilization is of the utmost importance for accurate analyses.

Fig. 5 schematically illustrates an automatic scanning arrangement utilizing the motors El and .6 driving arms 37 and 38, respectively, through the associated reduction gearings 433 and 48. As stated, arm 38 is moved at substantially twice the speed of arm 31 so that the angle be-.- tween arms 3| and 38 is substantially twice that between arms 3! and 31. The counting and scaling unit 45, having its input connected to Geiger counter 40, has its output applied to a recording potentiometer Hit. The chart ID! of the potentiometer is driven by a motor H32, preferably synchronous, in such manner that, with the chart calibrated in Bragg angle degrees, its calibrations will be synchronized with the characteristic Bragg angl s as read from goniometer 50. As arms 33, 33 move over quadrant 33, chart I! is correspondingly moved so that the movable needle or pen (not shown) of recorder M10 is always at a point on the chart corresponding to the Bragg angle determined from goniometer B. The pen is moved in accordance with the intensity of fluorescent radiation, as registered by Geiger counter 4t and translated by unit 45 for application to recorder Hi8. Consequently, a graphic qualitative analysis of a specimen is quickly produced on chart 101 by the automatic scanning arangement.

If chart H3] is suitably calibrated to indicate percentages of elemental constituents, a rapid quantitative analysis may also be produced by the automatic scanning arrangement. Such quantitative analyses require individual charts for each type of composition, such as for a low straight chromium alloy, a chrome-nickel austenitic alloy, etc. Additionally, the charts have independent percentage scales for each lemental constituent, such as a chromium scale, copper scale, iron scale, etc., dependent upon the type of alloy undergoing analysis. For analyzing quantitatively for a single element in an unknown specimen, charts may be used havin differently calibrated percentage scales for such element, each scale corresponding to a particular type of alloy, or the like. These charts are prepared empirically by fluorescent analysis of specimens of known percentage compositions, and their use obviates the necessity for comparative analyses utilizing standard specimens of known composition.

Referring to Fig. 5, a supply circuit is indicated as including conductors 563, Hi l. Operation of arms 3i, 38 in a clockwise direction is effected by a relay CW which is energized by operation of push button 3. Closure of contacts CW-l completes a holding circuit for the relay through closed contacts CCW-E of counterclockwise relay CCW, clockwise limit switch LS-i, and stop push button 5. Contacts CW-3 and CW- l close to energize all three motors 4!, it, and N32 for operation of th system in the clockwise scanning direction. The scanning may be continued until limit switch LS-l opens, or may be limited to a particular area of interest by operating stop push button 5.

counterclockwise scanning is effected in a similar manner by energizing counterclockwise relay CCW through momentary depression of push button 4. It will be noted that contacts CW-2 and CCW-2 interlock the relay circuits so that only one circuit can be closed at a time. While three motors are shown for the system, if greater assurance of synchronism of the chart movement with the goniometer movement is desired, chart it! can be driven by motor 4! or motor fit. Thereby, the chart operation is mechanically locked to the goniometer operation.

The automatic scanning system provides for rapid qualitative and/or quantitative analyses without the time consuming mathematical computations necessary with manual scanning, thus greatly expediting the analytical procedure.

.An outstanding feature of the apparatus is that the size of the specimens is not limited by the size of grooves 64, 64. Should it be desired to analyze a specimen which is too large to fit in one of these grooves, holder 66 can be readily removed by loosening studs 88 and detaching bar 2'! from T-bar 84. With bar 8? and panel 6| removed, the outsize specimen can be clamped to wall [3 directly in front of aperture 25. Should either specimen be smaller than an opening E5, 65', a sleeve or a shim of appropriate size may be inserted in the opening.

Fig. 6 is a reproduction of actual graphic analyses of two structurally similar alloys of the same predominant phase, both analyses being recorded on the same chart. The solid line A is the recorded analysis of an alloy of 18.25% chrome, 8.78% nickel, balance substantially iron, while the broken line B is th recorded analysis of an alloy of 25.14% chrome, 20.28% nickel, balance substantially iron. The respective curves were recorded on a quadrilaterally ruled chart having calibrated percentage scales for chromium, nickel and iron, the abscissae corresponding to characteristic Bragg angles.

By reference to the chart, it will be noted that the Ni K0. point of the broken line B, representing 20.28% Ni is a little over twice the magnitude of the corresponding point of the solid line A representing 8.78% Ni. Similarly, the Cr Kc peak of the broken line B, representing 25.14% C1 is about higher than the corresponding peak of solid line A, representing 18.25% Cr. The two Fe Kc peaks are likewise proportional to the respective Fe percentages.

The depicted chart has calibrated percentage scales for nickel, iron and chromium in austenitic alloys of the chromium-nickel type. For other types of alloys, differently calibrated percentage scales are used. Alternatively, the chart may have only chromium scales, for example, each calibrated for the chromium percentage in a different type of alloy. fhe latter type of calibrated chart is particularly useful in analyzing for a single constituent such as chromium, nickel, etc. Additionally, the charts are calibrated in accordance with the particular crystal analyzer used, such as rock salt, fluorite, etc.

Figs. '7, S and 9 schematically illustrate the invention analyzer as arranged for making comparative analyses by simultaneously irradiating both the standard and unknown specimens from a single source of primary radiation and recording the differentials of the percentages of the constituents to quantitatively analyze the unknown specimen. In these figures, the apparatus elements have been given the same reference numerals, primed or double-primed when duplicated, as used in Figs. 1 through 5.

In the arrangement of Fig. 7, the known specimen Hi and the unknown specimen it, both mounted in specimen holders (not shown) on outer wall surfaces of housing It are simultaneously irradiated by a single source of primary radiation, such as an X-ray tube 26 having two windows 23 and 23". The resulting characteristic secondary radiation from specimen 1B is rectified by collimator 3U, diffracted by crystal analyzer 35, and the component spectra at selected Bragg angles detected by a Geiger counter 453.;

The latter, and analyzer 35, are mounted on arms 38, 3'1, respectively, movable over quadrant 33 by synchronized motors, as previously described. The characteristic secondary radiation of specimen lli is rectified by collimator 30', diffracted and detected in the same manner, the corre-- i spending elements bearing the same reference characters primed.

The output of detector iii is applied, through leads iilS to a scaling and counting unit energized from source till. Similarly, the output of detector id is applied through leads it? to scaling and counting unit d5" lizewise energized from source it]. The outputs of units i5, it are applied, through leads 1'58, i 58, respectively, and in opposition, to the grid ii i of anelectronic valve Hi The latter has an anode M2 connected to 33+ through a recording potentiometer lee" energized from source it and having its chart movement coordinated with the movements of the goniometer arms, as described in connection with Fig. 5. Cathode iii of valve lid is schematically indicated :as grounded, with the grid bias being derived by an adjustabl resistancei-id.

In operation, the goniometers 5d, 5d are adi justed to known corresponding points where the outputs .of units 55, it are balanced, and resistance lid adjusted until the recorder movable element is on the zero percentage difference line of the recorder chart. The two specimens to, it are then simultaneously irradiated, and scanned in the manner described for Fig. 5. The differences between the outputs of units t5, i5 is recorded, on a properly calibrated recorder chart, as percentage difierentials at characteristic Bragg angles with the quantitative analysis of specimen 79 being known, that of specimen iii" is readily computed :from the graphic representation on the chart.

:Figs. 8 and.9 illustrate an alternative arrangement for simultaneously irradiating both specimens from a single source, such as X-ray tube 2% having a single window '23. The specimens iii, fiilflare arranged one above the other, in front of but at substantially different angles to window 23, a 90 relation being shown by way of example. A horizontal .lead shield ii'5 keeps the characteristic secondary radiation beams separated for rectification by appropriately directed collimators '39 and 36'. The remainder of the arrangement, and its operation, are identical to those of Fig. '7.

While anX-ray tube has been referred to as the source of primaryradiation, this has been by way of example only. To obtain the primary radiation incident upon the specimen, radiation sources .cother than an X-ray tube may be used, such as, for example, radium or a suitable isotope of a radio-active material.

While specific embodiments of the invention have been shown and described in detail to illustrate the application of the invention principles, it will beunderstood that the invention may be embodied otherwise without departing from such principles.

I claim:

1. In a-fluorescent spectra analyzer of .the type comprising a radiation source for directing primary radiation onto aspecimen to irradiate the same, a collimator for resolving the resulting characteristic secondary radiation emanating from the irradiated specimen, a diffraction grating arranged adjacent the exit end of the collimator inthe pathof the characteristic secondary radiation and-operative to separate the same into its component spectra, a radiation detector arranged to receive characteristic secondary radiationirom the grating, means mounting the grating detector for angular adjustment relative to each other and to the incident secondary radiation for detecting the component spectra at selected Bragg angles; a lead lined housing enclosing the radiation source and the entrance end of the collimator and having a side wall, said wall having an aperture therethrough and the radiation source and collimator being so arranged that the axes of the primary and secondary radiation beams intersect substantially adjacent the outer surface-of said Walland at the center of the aperture; a panel movably mounted on the outersurface of said wall, in 'suriace to-surface engagement therewith, and having a lead lining on its well engaging surface of an area greater than that of the aperture; said panel having an opening therethrough alignable with the wall aperture; and means operable to position a specimen on the outer side of said panel and overlying the opening therein; said panel being movable on said wall between a position in which its lead lining covers the wall aperture and a position in which the opening is aligned with the aperture.

2. Ina fluorescent spectra analyzer of the type comprising a radiation source for directing primary radiation onto a specimen to irradiate the same, a collimator for resolving the resulting characteristic secondary radiation emanating from the irradiated specimen, a diffraction grating arranged adjacent the exit end of the collimater in the path of the characteristic secondary radiation and operative to separate the same into its component spectra, a radiation detector arranged to receive characteristic secondary radiaticn from the grating, means mounting the grating and detector for angular adjustment relative to each other and to the incident secondary 'radiation for detecting the component spectra at selected Bragg angles; a lead lined housing en-' closing the generator and the entrance end of the collimator and having a side wall, said housing being substantially airtight and said collimator extending in sealed relation through a wall thereof a flexible air-tight enclosure connecting the outer end of the collimator to the detector and enclosing the diffraction grating and means operable to constantly maintain a uniform atmosphere other than air in said :housing, collimator, and enclosure to minimize or eliminate absorption of fluorescent spectra between the specimen and the detector.

3. In a fluorescent spectra analyzer of the type comprising a radiation source for directing primary radiation onto a specimen to irradiate the same, a collimator for resolving the resulting characteristic secondary radiation emanating from the irradiated specimen, a diffraction grating arranged adjacent the exit end of the collimator in the path of the characteristic secondary radiation and operative to separate the sameinto its component spectra, a radiation detector arranged to receive characteristic secondary radiation from the grating, means mounting thegrating and detector for angular adjustment relative to each other and to the incident secondary radiation for detecting the component spectra at selected Bragg angles; a lead lined housing onclosing the radiation source and the entrance end of the-collim tor and having a side wall, said wall having an aperture therethrough and the radiationsource and collimatorbeing so arranged that the axes of the primary and secondary radiation beams intersect substantially adjacent the outer surface of said wall and-at the center of the aperture; an elongated panel mounted in surface-to-surface engagement with the outer surface of said wall and 'reciprocable longitudinally thereof, and having a lead lining on its wall engaging surface of an area greater than that of the aperture; said panel having longitudinally spaced openings therein selectively alignable with the wall aperture; and means operable to position specimens on the outer side of said panel and each overlying an opening therein; said panel being movable on said wall between posit ns in wh its lead lining covers the wall aperture and positions in which the openings are selectively aligned with the aperture.

4. In a fluorescent spectra analyzer of the type comprising a radiation source for directing primary radiation onto a specimen to irradiate the same, a collimator for resolving the resulting characteristic secondary radiation emanating from the irradiated specimen, a diffraction gratting arranged adjacent the exit end of the collimator in the path of the characteristic secondary radiation and operative to separate the same into its component spectra, a radiation detector arranged to receive characteristic secondary radiation from the grating, means mounting the grating and detector for angular adjustment relative to each other and to the incident secondary radiation for detecting the component spectra at selected Bragg angles; a lead lined housing enclosing the radiation source and the entrance end of the collimator and having a side wall, said Wall having an aperture therethrough and the radiation source and collimator being so arranged that the axes of the primary and secondary radiation beams intersect substantially adjacent the outer surface of said wall and at the center of the aperture; an elongated panel mounted in surface-to-surface engagement with the outer surface of said wall and reciprocable longitudinally thereof, and having a lead lining on its wall engaging surface of an area greater than that of the aperture; said panel having longitudinally spaced openings therein selectively alignable with the wall aperture; means operable to position specimens on the outer side of said panel and each overlying an opening therein; mechanism, including an electric motor, operable to reciprocate said panel along said wall; control means operable to energize said motor; and means automatically operable to deenergize said motor whenever an opening is aligned with the aperture; the lead lining of said panel sealing the aperture in intermediate positions of said panel.

5. In a fluorescent spectra analyzer of the type comprising a radiation source for directing primary radiation onto a specimen to irradiate the same, a collimator for resolving the resulting characteristic secondary radiation emanating from the irradiated specimen, a diffraction grating arranged adjacent the exit end of the collimator in the path of the characteristic secondary radiation and operative to separate the same into its component spectra, a radiation detector arranged to receive characteristic secondary radiation from the grating, means mounting the grating and detector for angular adjustment relative to each other and to the incident secondary radiation for detecting the component spectra at selected Bragg angles; a lead lined housing enclosing the radiation source and the entrance end of the collimator and having a side wall, said wall having an aperture therethrough and the radiation source nd collimator being so arranged that the axes of the primary and secondary radiation beams intersect substantially adjacent the outer surface of said wall and at the center of the aperture; a slide mounted for longitudinal reciprocation on the outer surface of said wall; an elongated panel disengageably supported on said slide in surface-to surface engagement with the outer surface of said wall, and having a lead lining on its wall engaging surface of an area greater than that of the aperture; said panel having longitudinally spaced openings therein selectively alignable with the wall aperture; and means operable to position specimens on the outer side of said panel and each overlying an opening therein; said slide being movable between positions in which the lead lining of said panel covers the aperture and positions in which a panel opening is selectively aligned with the aperture.

6. In a fluorescent spectra analyzer of the type comprising a radiation source for directing primary radiation onto a specimen to irradiate the same, a collimator for resolving the resulting characteristic secondary radiation emanating from the irradiated specimen, a diffraction grating arranged adjacent the exit end of the collimator in the path of the characteristic secondary radiation and operative to separate the same into its component spectra, a radiation detector arranged to receive characteristic secondary radiation from the grating, means mounting the grating and detector for angular adjustment relative to each other and to the incident secondary radiation for detecting the component spectra at selected Bragg angles; a lead lined housing enclosing the radiation source and the entrance end of the collimator and having a side wall, said wall having an aperture therethrough and the radiation source and collimator being so arranged that the axes of the primary and secondary radiation beams intersect substantially adjacent the outer surface of said wall and at the center of the aperture; a slide mounted for longitudinal reciprocation on the outer surface of said wall; an elongated panel disengageably supported on said slide in surface-to-surface engagement with the outer surface of said wall, and having a lead lining on its Wall engaging sur-- face of an area greater than that of the aperture; said panel having longitudinally spaced openings therein selectively alignable with the wall aperture; means operable to position specimens on the outer side of said panel and each overlying an opening therein; and wedge means cooperable with said slide to force said panel into tight surface engagement with the outer surface of said wall; said slide being movable between positions in which the lead lining of said panel covers the aperture and positions in which a panel opening is selectively aligned with the aperture.

'7. In a fluorescent spectra analyzer of the type comprising a radiation source for directing primary radiation onto a specimen to irradiate the same, a collimator for resolving the resulting characteristic secondary radiation emanating from the irradiated specimen, a diffraction grating arranged adjacent the exit end of the collimator in the path of the characteristic secondary radiation and operative to separate the same into its component spectra, a radiation detector arranged to receive characteristic secondary radiation from the grating, means mounting the grating and detector for angular adjustment relative to each other and to the incident secondary radiation for detecting the component spectra at selected Bragg angles; a lead lined 11. In a fluorescent spectra analyzer of the type comprising a radiation source for directing primary radiation onto a specimen to irradiate the same, a collimator for resolving the resulting characteristic secondary radiation emanating from the irradiated specimen, a diffraction grating arranged adjacent the exit end of the collimator in the path of the characteristic secondary radiation and operative to separate the same into its component spectra, a radiation detector arranged to receive characteristic secondary radiation from the grating, and means mounting the grating and detector for angular adjustment relative to each other and to the incident secondary radiation for detecting the component spectra at selected Bragg angles, the mounting means comprising a pair of radial arms relatively adjustable about a center adjacent the exit end of the collimator, one of said arms supporting said grating for angular adjustment relative to the axis of said collimator and the other arm supporting said detector for angular adjustment relative to said grating and the axis of said collimator; an automatic specimen scanning system including a movable chart recorder having its chart calibrated in Bragg angles; means operative to apply the output of said detector to the indicating mechanism of said recorder; and driving means associated with each of said arms and with said chart and operable to drive said arms '9 and said chart in coordinated relation with each other to produce a record of the relative intensities of secondary radiation at characteristic Bragg angles.

12. In a fluorescent spectra analyzer of the type comprising a radiation source for directing primary radiation onto a specimen to irradiate the same, a collimator for resolving the resulting characteristic secondary radiation emanating from the irradiated specimen, a diffraction grating arranged adjacent the exit end of the collimator in the path of the characteristic secondary radiation and operative to separate the same into its component spectra, a radiation detector arranged to receive characteristic secondary radiation from the grating, and means mounting the grating and detector for angular adjustment relative to each other and to the incident secondary radiation for detecting the component spectra at selected Bragg angles, the mounting means comprising a pair of radial arms relatively adjustable about a center adjacent the exit end of the collimator, one of said arms supporting said grating for angular adjustment relative to the axis of said collimator and the other arm supporting said detector for angular adjustment relative to said grating and the axis of said collimator; an automatic specimen scanning system including a movable chart recorder having its chart calibrated in Bragg angles; means operative to apply the output of said detector to the indicating mechanism of said recorder; driving means associated with each of said arms and with said chart and operable to drive said arms and said chart in coordinated relation with each other to produce a record of the relative intensities of secondary radiation at characteristic Bragg angles; and a conjoint control system for said motors including manually operable circuit closure means, automatic circuit breaker means operative at the limits of movement of the arms, and manually operable circuit breaker means.

13. In a fluorescent spectra analyzer of the type comprising a radiation source for directing primary radiation onto a specimen to irradiate the same, a collimator for resolving the resulting characteristic secondary radiation emanating from the irradiated specimen, a difiraction grating arranged adjacent the exit end of the collimator in the path of the characteristic secondary radiation and operative to separate the same into its component spectra, a radiation detector arranged to receive characteristic secondary radiation from the grating, means mounting the grating and detector for angular adjustment relative to each other and to the incident secondary radiation for detecting the component spectra at selected Bragg angles; a lead lined housing enclosing the generator and the entrance end of the collimator and having a side wall, said housing being substantially air-tight and said collimator extending in sealed relation through a wall thereof; a flexible air-tight enclosure connecting the outer end of the collimator to the detector and enclosing the diffraction grating; and means operable to constantly maintain a vacuum in said housing, collimator, and enclosure to minimize or eliminate absorption of fluorescent spectra between the specimen and the detector.

14. In a fluorescent spectra analyzer of the type comprising a radiation source for directing primary radiation onto a specimen to irradiate the same, a collimator for resolving the resulting characteristic secondary radiation emanating from the irradiated specimen, a diffraction grating arranged adjacent the exit end of the collimator in the path of the characteristic secondary radiation and operative to separate the same into its component spectra, a radiation detector arranged to receive characteristic secondary radiation from the grating, means mounting the grating and detector for angular adjustment reltative to each other and to the incident secondary radiation for detecting the component spectra at selected Bragg angles; a recorder chart calibrated in characteristic Bragg angles and having percentage scales for elemental constituents calibrated in accordance with known relations of spectral intensities to element percentages; and means constructed and arranged to indicate on said chart at each characteristic Bragg angle the spectral intensity; whereby an unknown specimen may be simultaneously quantitatively and qualitatively analyzed.

15. For use in a fluorescent spectra analyzer of the type comprising a radiation source for directing primary radiation onto a specimen to irradiate the same, a collimator for resolving the resulting characteristic secondary radiation emanating from the irradiated specimen, a diffraction grating arranged adjacent the exit end of the collimator in the path of the characteristic secondary radiation and operative to separate the same into its component spectra, a radiation detector arranged to receive characteristic secondary radiation from the grating, means mounting the grating and detector for angular adjustment relative to each other and to the incident secondary radiation for detecting the component spectra at selected Bragg angles, the mounting means comprising a pair of radial arms relatively adjustable about a center adjacent the exit end of the collimator, one of said arms supporting said grating for angular adjustment relative to the axis of said collimator and the other arm supporting said detector for angular adjustment relative to said grating and the axis of said collimator, an automatic specimen scanning system including a movable chart 2?; recorder, means operative to apply the output of said detector to the indicating mechanism of said recorder, driving means associated with each of said arms and with said recorder and operable to drive said arms and said recorder in coordinated relation with each other to produce a record of the relative intensities of secondary radiation at characteristic Bragg angles; a chart for said recorder calibrated in characteristic Bragg angles and having percentage scales for element constituentscalibrated in accordance with known relations of spectral intensities to element percentages, to quantitatively determine the-composition of the test specimen.

MARCEL A; CORDOVI.

References Cited in the file Of this patent UNITED STATES PATENTS Number OTHER, REFERENCES A new Precision X-Ray Spectrometer by W 13 15 ter Soller, Physical Review, vol. 24, 1924, pp.

A High-Temperature X-Ray Camera for Precision Measurements, Jay, Physical Society of London Proceedings, vol. 44; 1933, pages 635-642.

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