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Jan- 29, 1963 K. A. KIESEL ETAL 3,076,093 RADIO FLUID DETECTOR Filed Oct. 28', 1958 2 Sheets-Sheet 1 56 6O 62 54 —-Gos \58 57 Q I8 70 \ |2 T2 - 64 7 ‘__—' \. . 68 y ‘ ‘ 8l6 48 74' 42 75~ Amplifier 59 <—-Gus 78 46 80~— Counter F|g.|. Paint “xxgmm WITNESSES ' INVENTORS Kenneth A. Kiesel, Edward L. Web! Jan. 29, 1963 K. A. KIESEL ETAL 3,076,093 RADIO FLUID DETECTOR Filed Oct. 28, 1958 2 Sheets-Sheet 2 United States Patent 0 "me I 3,076,093 Patented Jan. 29, 1963‘ 1 2 3,076,093 tect minute quantities of low energy beta emitting ?uids. In the course of the forthcoming detailed description of the invention, these and other objects, features and advantages of the invention will be elaborated upon, par RADIO FLUID DETECTOR Kenneth A. Kiesel and Edward L. Webb, Baltimore, Donald V. Smith, Catonsviile, and Zane L. Collins, 'Linthicum Heights, Md., assignors to Westinghouse Electric Corporation, East Pittsburgh, Pa, a corpora tion of Pennsylvania Filed _Oct. 28, 1958, Ser. No. 770,207 7 Claims. (Cl. 250-415) ticularly in conjunction with the accompanying drawings, wherein: FIGURE 1 is a longitudinally sectioned view of a ra diation detector constructed in accordance with the in vention andshown in connection with external amplifying 10 and metering circuitry; This invention relates to a radiation detector adapted , FIG. 2 is a cross-sectional view showing the radiation detector of FIG. 1 and taken along reference line 11-11 particularly for use with radioactive gases or other ?uids and, more particularly, to gases exhibiting a short range radioactivity such as beta emission. thereof; radioactivity and particularly that associated with radio thereof; and FIG. 3 is a cross-sectional view showing the radiation The measurement of the concentration intensity of 15 detector of FIG. 1 and taken along reference line III-1H FIG. 4 is an enlarged sectional view of a wall portion gases is extremely important inasmuch as the permissible of the radiation detector shown in FIG. 1. tolerance levels of radioactive gases is generally rather There is provided in accordance with the invention low. A radiation detector employed for determining this radiation intensity, therefore, must be extremely sensitive. 20 a radiation detector for use in detecting low energy'beta The gases most frequently of interest are beta emitters, the measurement of which entails a number of problems outlined below. Ionization chambers have been em emitting materials which may be present in a surround- 1 ’‘ ing medium or environment such as air in'relatively minute quantities. The sensitivity of the radiation de-i tector of the invention is increased considerably by em ployed in the past for measuring beta emitters with satis factory results; however, these detectors are necessarily 25 ploying a scintillating phosphor which is sensitive to beta' particles and by introducing the beta emitting material, in large and difficult to handle. The ionization chamber moreover is inclined to instability when employed over ?uidized form, as close to and over as large an area of extended periods of time. The radio ?uid detector frequently is employed in con nection with atomic plants wherein radioactive gases such the phosphor as is practical. Means are associated with. as Kr“, Xe133 and Xe135 are likely to be encountered. The energy level of the beta rays from such gases is relatively low and as a result their penetration path in air amounts to only a few inches. These gases, however, obviously are hazardous to breath, and therefore their detection and measurement is vital. Because of the fact that the emitted beta particles are absorbed by a few inches of air, the active portion of the detector must be arranged in proximity to the gas being monitored or de tected, and additionally, the surface area of the detector must be comparatively large to achieve the extreme sen the detector for collecting the light output of the phosphor and translating the same into an electrical signal . for subsequent ampli?cation and measurement. The radiation detector of the invention is arranged so that the aforementioned phosphor and other components of the detector are relatively insensitive to a high level of gamma background radiation. nated against. The atomic plants mentioned previously Referring now more particularly to the drawings, the invention as exempli?ed therein comprises a spheroidal shell or housing 10 to which a photomultiplier tube hous ing 12 is secured. The housing 12 desirably is of a gen erally cylindrical contour and is threaded at its open end into an aperture 14 formed in the wall of the shell 10. In order to seal the housings 10 and 12,- the housing 12 is provided with an annular ?ange 16 which, when the housing 12 is threaded into the shell 10, is adapted to compress a gasket 18 between the ?ange 16 and‘the adja a novel and ef?cient radiation detector. provided with‘opposing ?anges 24 and 26,trespectively. More speci?cally, it is an object of the invention to provide a detector of the character described, adapted for use in detecting relatively low range beta emitters par ticularly when in ?uid form. Another object of the invention is the provision of a These ?anges 24 and 26 are secured together by a plu rality of mounting bolts 28 which are inserted respec sitivity required. , Since the activity of interest in most radio-active gases is beta emission, any gamma radiation must be discrimi . frequently have areas of high gamma activity, and ac-‘ 45 cent wall portion of the shell 10. For ease in fabricating the radiation detector, the shell cordingly, the use of conventional beta detectors is not 10 desirably is formed from hemispherical portions 20 practical. The use of gamma shielding for the detector and 22. To the right-hand hemispherical portion 22, as‘ not only would make the detector bulky and heavy but would be impractical from the standpoint of measuring 50 viewed in FIG. 1 of the drawings, the photomultiplier housing 12 is secured in the manner described previous relatively low energy beta emission. ly. Each of the hemispherical portions 20 and 22 are It is accordingly, an object of the invention to provide radiation counter adapted for detecting‘ and measuring tively through suitable apertures in the ?ange 24 and threaded into tapped apertures in the ?ange 26. ‘ One of the ?anges, for example, the ?ange 26 is pro vided with an annular groove 34 disposed inwardly of beta activity and insensitive to background gamma ra the array of mounting bolts 28. Into the groove 34 is diation. A further object of the invention is the provision of a beta detector adapted for use in measuring the intensity inserted a sealing O-ring 36 whereby the junction between the ?anges 24 and 26 is sealed upon tightening the mount ing bolts 28. As better shown in FIG. 4 of the drawings, the internal surfaces of the hemispherical portions 20 and 22 are of radioactive gases or other ?uids in the presence of a high level of gamma radiation. 65 coated with a layer 38 of a re?ective White paint such as Still another object of the invention is the provision of a beta detector for use in an area-of high gamma radia White Re?ector Lacquer made by Interchemical Corpora tion wherein the necessity of gamma shielding is elimi nated. A further object of the invention is the provision of an extremely sensitive radiation detector adapted to de tion, 350 Fifth Avenue, New York, New York as their» Ma 922F. Subsequently, a layer 40 of beta or electron sensitive phosphor is applied to the inner surface of the an’ shell 10. Any suitable phosphor in this category can be 3 3,076,093 employed for the coating or layer 40, for example, zinc sulphide. The coating 40 desirably is applied in ac cordance with known methods, for example, by spraying a suspension of pulverulent phosphor in a suitable carrier. In this manner, the entire inner surface of each of the hemispherical portions 20 and 22 (FIG. 1) are coated 4 reference numeral 76 and labeled “ampli?er” in the ar rangement of FIG. 1. The output of the amplifying circuitry 76 is coupled as indicated by conductor 78 to suitable counting or metering circuitry denoted by the numeral 80 and labeled “counter" in FIG. 1. The cathode 7d of the photo tube is disposed adjacent the inner periphery of the shell 10' and the lens 64 de Care should be taken in applying the phosphor, how sirably is capable of a wide angle of resolution, in ac ever, to ensure that the phosphor particles are not covered cordance with well-known optical principles, so that sub by a relatively thick layer of the carrier. 10 stantially all of the scintillations produced in the phosphor The hemispherical portion 22 is provided with an coating 40 are visible to the cathode 70 of the photomul additional opening 42 through which an inlet conduit tiplier tube. By virtue of this fact and the fact that the with a phosphor layer 40. 44 is inserted. The inlet conduit 44 is provided with a radioactive material is emitted as close as practical to the valve 46 and after entering the shell 19‘ extends around phosphor coating 40, the radiation detector described a major proportion of the inner periphery thereof. herein is rendered extremely sensitive in detecting beta As better shown in FIG. 3 of the drawings, the in particles. On the other hand, the absence of a relatively ternal portion 44a of the inlet conduit in this example low-density atmosphere within the shell 10, the use of follows generally the path of the great circle of the sphe relatively thin coating layers 38 and 40, and the use of roidal shell 10 and is juxtaposed to a photomultiplier a shell 10 having relatively thin wall portions, renders the tube 48. The inlet tube 44 terminates within the shell 20 radiation detector insensitive to gamma radiation. It has 10 in a closed end portion denoted generally by the been found, as a matter of fact, that the radiation detec reference. character 50. In this arrangement of the in tor described herein can operate in a background of vention, the internal portion 44a of the inlet tube is pro gamma activity of the order of 20 milliroentgens per hour vided with a plurality of spaced ?ow apertures 52 extend and with a beta sensitivity of 4X10‘8 to 4X 10.5 micro— ing transversely through the wall of the tube poriton 44a. curies per cubic centimeter. As better shown in FIGS. 1 and 4 of the drawings, the It will be apparent from the foregoing description that apertures 52 are positioned so that a medium containing a novel and efficient form of radiation detector has been radioactive material can ?ow outwardly of the conduit described herein. The accompanying descriptive ma portion 44a via the apertures 52 at positions relatively terials have been presented for purposes of exemplifying close to the adjacent phosphor layer 40. The purpose of the invention, and are not, therefore, intended to be this arrangement is to minimize the absorption of the beta limitative thereof. particles by any of the ?uid media or atmosphere con Accordingly, numerous modi?cations and embodiments tained within the shell 10 before the beta particles con of the invention will occur to those skilled in the art with tact the phosphor layer 40. Inasmuch as the pressure out departing from the spirit and scope of the invention. within the shell 10 is substantially at atmospheric pres 35 For example, the detector disclosed herein is readily sure, the ionization or secondary electron emission in adaptable for use with ?uidized, alpha-emitting material, duced within the aforesaid ?uid medium by gamma radi ation is negligible. The ?uid medium thus admitted to the interior of the shell 10 is exited therefrom by means of an outlet con duit 54 provided with a suitable valve means 56 for ad justing the ?ow therethrough. The inner open end 55 of the outlet conduit is inserted through an aperture 57 in the hemispherical portion 22 and to preserve the integrity of the shell or- housing 10 both the outlet conduit 54 and the inlet conduit 44 can be sealed at their points of entry into the shell 10 by means of the annular sealing welds 59. The outlet conduit 54 is coupled to the suctional side 5.8. of a, conventional blower 60 whereby the ?uid medium particularly with respect to short-range alpha particles. What is claimed as new therefore is: l. A radiation detector comprising a hollow shell adapted for enclosing a ?uid medium therein, a scintilla tional phosphor coating applied to an inner surface of the wall of said shell, a conduit disposed in said shell adjacent said inner surface for conducting a ?uid into said shell and having aperture means therein for emitting 45 said ?uid to the interior of said shell at positions closely adjacent said coating, and means for translating light emitted from said coating into an electrical indicating signal. 2. A radiation detector comprising a hollow shell is drawn through the shell 10 of the detector. Since the 50 adapted for enclosing a ?uid medium therein, a scintilla ?uid medium may contain radioactive material as dis tional phosphor coating applied to an inner surface of the cussed previously, the discharge of the blower 60 desir wall of said shell, a conduit disposed in said shell adjacent ably is coupled to a suitable waste disposal arrangement said inner surface for conducting a ?uid into said shell and (not shown) by means of conduit 62. having aperture means therein for emitting said ?uid to In‘ the operation of the radiation detector according to 55 the interior of said shell at positions closely adjacent said the present understanding of the invention, a ?uid me~ coating, means for withdrawing said ?uid from said shell dium containing radioactive beta emitting material is whereby samples of said ?uid can be monitored continu drawn into the inlet conduit portion 44a and is released ously, and means for translating light emitted from said therefrom through the plurality of apertures 52. The coating into an electrical indicating signal. beta particles emitted by the radioactive material con 3. A radiation detector comprising a hollow spheroidal tained within the ?uid react with particles of the phos shell capable of enclosing a ?uid therein, a phosphor coat phor coating 40 to produce scintillations or light pulses ing applied to substantially the entire internal surface of therein. The scintillations of the coating 40 are collected the wall of said shell, means for conducting a ?uid to by a lens. 64- as denoted by light rays 66 and are trans a substantial area of said coating, means for translating mitted to the adjacent photo cathode window 70' of the 65 light emitted by said coating into an electrical indicating signal, said last-mentioned means including a photo-tube photomultiplier tube 48 as denoted by the parallel light rays 68. Suitable photomultiplier tubes 48 are commer cially available and need not be described here in detail, save to say that the tube 48 is mounted in a socket de having a cathode mounted adjacent the inner wall sur face of said spheroidal shell, and a light collecting lens mounted within said shell and adjacent said cathode noted generally by the reference numeral 72. A source 70 whereby light from substantially all portions of said coating is collected and transmitted to said cathode. (not shown) of high voltage is coupled to the socket 72 4. 'A radiation detector comprising a hollow shell and thence to the tube 48 by suitable leads (not shown). adapted for enclosing a ?uid medium therein, a phos In the arrangement shown, the output signal of the phos phor coating ‘applied to an inner surface of said shell, phor tube 48 is coupled, as designated by a conductor 74 for conducting a ?uid into said shell and for con to suitable external amplifying circuitry denoted by the 75 means ducting said ?uid to a substantial area of said coating, 3,076,098 5 means for translating light emitted from said coating into 6 7. A radiation detector comprising a hollow shell ca an electrical indicating signal, said ?rst-mentioned means including an inlet conduit extending through said shell and adjacent the internal surface thereof, said conduit having a plurality of ?ow apertures extending through the wall thereof and positioned adjacent said coating. 5. A radiation detector comprising a hollow shell adapted for enclosing a ?uid medium therein, a phosphor. pable of enclosing a ?uid therein, a phosphor coating ap plied to a substantial portion of the internal surface of for translating light emitted from said coating into an electrical indicating signal, said ?rst-mentioned means in cluding an inlet conduit extending through said shell and periphery of said shell, said inner length having a plu rality of flow apertures extending transversely there the wall of said shell, means for conducting a ?uid to a substantial area of said coating, a photo-tube mounted within said shell and having a photo-cathode disposed ad jacent the inner periphery of said shell whereby said sub stantial portion of the internal surface of said shell is visible to said cathode, said ?rst-mentoned means includ coating applied to an inner surface of said shell, means for conducting a ?uid into said shell and for conducting 10 ing an inlet conduit extending through a wall of said shell and having a length thereof extending about the inner said ?uid to a substantial area of said coating, and means through and disposed adjacent said coating, said inlet adjacent the internal surface thereof, said conduit having 15 conduit length being juxtaposed to said photo-cathode. a plurality of flow apertures extending through the wall References Cited in the ?le of this patent thereof and positioned adjacent said coating, and a second conduit extending through the wall of said shell for with UNITED STATES PATENTS drawing ?uid emitted from said apertures from said shell. 2,681,416 Thompson __________ __ July 15, 1954 6. A radiation detector comprising a hollow spheroidal 20 2,755,391 Keyes _______________ __ July 17, 1956 shell capable of retaining a ?uid therein, a phosphor coat 2,884,529 Eggler et a1. __________ __ Apr. 28, 1959 ing deposited upon the internal surface of the wall of said 2,900,516 Davis et a1 ___________ _.. Aug. 18, 1959 shell, an inlet conduit extending through a wall of said 2,900,518 Good _______________ __ Aug. 18, 1959 shell and disposed adjacent said coating, said conduit 2,961,541 Ruderman ___________ __ Nov. 22, 1960 extending around a substantial proportion of the inner 25 3,005,100 Thompson ___________ __ Oct. 17, 1961 circumference of said shell and following the path of a OTHER REFERENCES great circle of said shell, said conduit having a plurality of ?ow apertures extending transversely through a wall Scintillation Counter for Assay of Radon Gases, by portion thereof and disposed in proximity to said coat Van Dilla et al., Nucleonics, February 1955, vol. 13, No. ing, and means juxtaposed to said inlet conduit for trans 30 2, pages 68 and 69. lating light emitted by said coating into an electrical indi cating signal.