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Патент USA US3076103

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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
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Amplifier
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Counter
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Paint
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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.
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