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Sem, 249 EM@ 4
`
_ w. E. sHouPP
MEASÚRING AÍ’PARATUS
Filed Dec. 9, 1941
wlTNl-:ssr-:s:
I
INVVENTOR-
I
NZZ/iam E.' Sha/pp,
BY
i `
_
ATTORNEY
Patented Sept. 24, 1946
2,4%,230
UNITED STATES PATENT GFFICE
2,408,230
A
MEAsUarNG APPARATUS
William E. Shoupp, Pittsburgh, Pa., assignor to
Westinghouse Electric Corporation, East Pitts
burgh, Pa., a corporation of Pennsylvania
Application December 9, 1941, Serial No. 422,271
11 Claims.
l
This invention relates to measuring apparatus
and, more particularly, to devices for indicating
(Cl. Z50-83.6)
2
cordance with this invention, the counter tube is
modiñed by adding to its elements recited a
the presence of corpuscular radiation.
coating 5 to the inner wall of the cylinder 3 of
Radioactive substances form a source of radia
such material which is capable of atomic iission
tions of particles, the presence of which may beY C: in the presence of neutron particles. Uranium
indicated by suitable sensitive devices which re
or thorium, among other elements, are particu
spond to the electrical charges carried by such
larly disrupted b-y neutron bombardment._ Neu
particles. In the atomic disintegration, we íind
trons penetrate glass and similar materials, and,
that in the atomic structure there are parti
therefore, the envelope 2 offers no impedient to
cles which do not possess an electrical charge of
their passage. The nuclear disintegration pro
any kind.
These particles are defined as neu
trons. As this definition indicates, these parti
cles are neutral and will not be attracted by
electrical fields, and their presence will not
change the potential charge-equilibrium of mat
duced by the iission of the uranium or thorium
atoms results in the formation of new nuclei pos
sessing strong ionization properties which4 will
ionize the space within the counter tube.
„
These new nuclei or fission particles resulting
ter with which they may come into contact. The
from the neutrons striking the uranium or tho
methods heretofore used for indicating charged
rium cause very high ionization, so that the volt
particles, therefore, cannot be applied for indi
age diiîerence between the electrodes of the
cating the presence of neutron radiation.
counter tube may be set suiliciently low as to
The present invention has for its object to in 20 make the counter respond only to radiation due
dicate the presence of neutron particles and also
to nuclear fission and not to any other corpuscu
count the number of such particles within a con
fined space.
lar radiations, such as alpha or beta rays, ,or
A particular feature of the invention is that
the phenomenon of atomic fission observable in
nuclear physics is utilized as a secondary elîect
producing medium for the indication of neutron
consequently the registered counts, will then be
radiation.
A particular advantage in utilizing
atomic ñssion is that apparatus used to detect
particles having a definite electrical charge may
be employed, with simple modification in ac
cordance with this invention, to indicate neutron
radiation.
'
Other features and advantages will be appar
ent from the following description of the inven
tion, pointed out in particularity by the append
ed claims, and taken in connection with the ac
electrons that may be present. The fission, and
a measure of the neutron intensity. Generally,
in counter tubes, once ionization starts the elec
trons formed in the ionized gaseous atmosphere
in their acceleration form more electrons, creat
ing an electron avalanche. If the discharge is
to be self-maintained, it requires a source of
electrons other than that of the gas molecules.
It was found that the source of these electrons
is the photoelectrons ejected from the cylinder
3 by the quanta that radiate from the excited
positive ions formed by the electrons that set up
the avalanche. For this reason, once a discharge
is started in the counter tube, means must be
companying drawing, in which:
provided for extinguishing it rapidly in order to
The ñgure shows schematically the circuit of
bring the tube to a sensitive condition for the
a counting and recording apparatus responsive 40 next neutron particle. It is important to note
to neutron particles.
.
Referring to the figure, a counter tube lis
shown schematically in cross-section comprising
that the neutron induced fission is much more
probable than the iission which may be induced
by gamma rays, and no serious correction. will be
necessary in the apparatus in accordance with
within which is a conducting cylinder 3. Co
this invention to cancel the eiîect which gamma
axially to this cylinder is stretched a ñne insu
'rays may produce.
lated wire 4. The counter tube just described
Coupled to the counter tube l is a vacuum tube
is known in the art as a “Geiger counter,” and
circuit shown here in a simplified form reduced
is used in connection with suitable electrical ap
to the essential elements of an operating struc
paratus to respond to the presence of charged 50 ture. For the sake of simplicity, individual bat
particles which will produce ionization between
teries are shown as the sources of operating po-the conducting cylinder and the insulated wire.
tentials for the tubesand for the counter tube.
However, since neutrons are particles devoid of
It is, of course, understood that these batteries
electrical charge, they will not produce ionization
may be replaced by a suitable power supply op
in the counter tubes known in the art. In ac
erating from commercial power circuits. The
a suitable housing 2 of glass or other material
2408,23()
3
4
fore, would maintain conductivity if the applied
tubes used are shown to be of the cathode-heater
type, the ’filament circuit being omitted, since it
voltage between the cylinder 3 and the wire 4 is
not removed. However, the circuit components
are so proportioned that the voltage drop due to
anode current of the tube 8 is Isufficiently high
t0 lower the potential difference between the cyl
inder 3 and the wire 4 to a Value which removes
is well known that the cathodes are heated by
filaments which may receive energy from vari
ous types of sources of current. The wire 4 is
connected to the anode 1 of the tube 8 and also
to the anode load resistor 9, which terminates at
the initial potential between these element-s for
maintaining ionization. In other words, the tube
the positive terminal of the battery Iii. The
battery II is connected in series therewith, and
8 acts as a low resistance, short-circuiting the
counter tube elements and the discharge in the
counter tube rwill be extinguished. As soon as
there is no conductivity, the grid I6 of the tube
3 returns to its normal negative charge, and anode
-tery II and also to the positive terminal of the 15 current in the tube ceases. The voltage equilib
rium is again restored between the cylinder 3
battery I4. The latter is in series with the re
and the wire 4 to a high value for the next ionizan
sistor I5 which connects to the control> grid lIS
tion due to fission of the deposit. The rate of con
of the tube 8 and also to the Ycylinder 3 of the
ductive energization and restoration to non-con~
counter tube I. In parallel with the resistor I5
the screen grid electrode I2 of the tube 8 is sup
plied 'with potential from the battery I I, in that
the screen grid I2 is connected to the junction
point between the two batteries. The cathode
I3 connects to the negative terminal of theAbat
i is the condenser I8.
20 ductivity is determined by the time constant of
the resistor I5 and the capacity I8.
I claim as my invention:
1. In 'a counter for indicating- neutron particles,
The output of the tube 8 between anode and
cathode is Vcoupled lto the input circuit of vthe aii`1~
plifier tube 20 by means of the coupling condenser
a counter tube including a pair of discharge velec
trodes in a gaseous atmosphere, 'material capable
of atomic ñssion under neutron bombardment,
The
2l which
biasing
connects
potential
to the
of grid
thè 'grid
22 of22the tube.
derived
from the battery 23 between cathode 2ï! in series
_with 'the grid load resistance 25. The amplifier
tube 2G is also of the .screenY grid type having a
screen grid 26 which is supplied 1‘with operating
potential from the battery 21. The anode 23 of
thè
of the
tube
electrom‘agnet
2'0 connects to
3l,the
a'ndOperating
is 'supplied
winding
with op
erating potential from the vbattery 32 in series with
thereby liberating radiation causing ionization of
said atmosphere, associated I'with one of said elec
trodes, and an ionization responsive circuit con~
30 nected between said electrodes.
2. In a counter for indicating the intensity ci
neutrons, a counter tube exposed to neutron radi~
ation, a pair of discharge electrodes in a gaseous
atmosphere for lsaid tube, one of which is at a
the battery 2l. The plunger 33 of the electro
magnet 3| is ?n'echanicallyglinked >with the Ashaft 35 positive potential with Arespect to the other, mate
rial capable of atomic fission under neutron bom
35 of a recording device. The latter operates in
bardment, thereby liberating radiation causing
the Well known manner that for each -m'oven'ieiit
ionization of said atmosphere, associated with
of the shaft 35 caused by the plunger 33 a num
said negatively chargedelectrode, and an ioniza
ber 'will appear, whereby every Yino'verm-:nt of the
tion responsive circuit connected between said
shaft is -'successively indicated within the number
electrodes.
range that the recording 'devicefm'aîy have.
3. A counter in accordance with claim 2 in
Referring to the operation of the circuit, the
which said material is in the Yform of a coating'cf
counter tube is usually operated at a pressure of
uranium.
a few 'centimeters of gas. A polarizing voltage of
V4. A counter in accordance with claim 2 in
a potential 'positive with respect to the Yc'ylir'ider
which said material i's in the form of a coating
is applied to the wire 4 from Athe batteries I4, ‘l I.
and Il] in series. In following the circuit, itis
ofk thorium. ' '
5.4 A discharge device comprising an elongated
seen that 'the ‘extreme ‘negative ‘terminal 'or the
conductor in a gaseous atmosphere, a cylindrical
series combination off batteries connects through
the resistor I5 to v'the 'cylinder 3, whereas the eX 50 conductor encircling said elongated conductor
and a coating of a material capable of atomic
treme positive terminal is 'connected through the
fission under neutron bombardment, thereby'lib»
anode resistor S to the wire '4. The 'voltage pro
erating radiation causing ionization of said at
duced by the batteries is of such'magnitude that
mosphere, on the inner surface of said cylindrical
it will vnot break Ydown -the gap between the Ywire
conductor.
4 and 4the cylinder 3. When the fission material
6. A discharge device comprising an >inner con
coating 5 is exposed t'o neutron particles, the
ductor in a gaseous atmosphere, an cuter con~
fission of the material, as stated above, Vproduces
ductor encircling said inner conductor and a
fission particles which liberate electrons and ions
coating of a material capable of atomic 'ñssicn
in the 'gas so that an velectrical discharge occurs
under neutron bombardment, thereby liberating
between the wire and the cylinder. -The strong
radiation causing ionization of said atmosphere,
electric ñeld near the -wire >will obtain suiiicient
on the inner surface of said outer conductor.
energy to ionize the gas. The ionization permits
7. discharge device comprising a gas-tight
'electrical conductivity between the wire 7l and
envelope of a material that is penetrated by neu
the cylinder 3,. When this happens, the grid It? of
the tube 8 'will become positive and the resultant 65 trons, said envelope having therein an'a‘ttenuatod
gaseous medium, Vvan inner conductor, an outer
current produces a voltage drop across resistor ’9.
conductor encircling said 'inner conductor 'and a
The change of voltage across resistor "9 'istra-ns»V
coating 'of a "material capable of 'atomic fission
mitted to the grid 22 >of the amplifier tube 2U by
under neutron bombardment, thereby liberating
the discharge of ythe condenser 2l. The impulse
which the grid 22 receives is then amplified by 70 radiation causing ionization of said atmosphere,
the tube 2B and results in a plate ‘current change.
The plate current ñowin'g through the winding 3E!
will cause the plunger 33 to operate and move‘the
shaft 35 of the recorder.
A breakdown in the counter tube, las »stated -bs
on the inner surface of said outer'conductor.
8. In combination, a gas-tight tube lincluding
a gaseous atmosphere anda pair of discharge
electrodes, one of said electrodes «bearing a mater
75 rial capable of atomic íission vunder neutron bom
5
2,408,230
6
bardment, thereby liberating radiation causing
said principal electrodes, a second impedance and
ionization of said atmosphere, a circuit intercon
necting said electrodes comprising a source of
direct-current voltage in series with a high im
a source of direct-current voltage interconnecting
said one of said principal electrodes to the other
pedance connected between said electrodes, and
means responsive to the magnitude of current ñow
through said impedance.
è; l
9. In combination, a gas-tight tube including a
gaseous atmospherel and a pair of discharge elec
trodes, one of said electrodes being a ‘substance
chosen from the group comprising uranium and
thorium, a circuit interconnecting said electrodes
comprising a source of direct-current voltagefïin
series with a high impedance connected between
said electrodes, and means responsive to the mag
nitude of current ñow through said impedance', '
10. In combination, a gas-tight tube including
a gaseous atmosphere and a pair of discharge elec
trodes, one of said electrodes being a material
capable of atomic ñssion under neutron bom-l
bardment, thereby liberating radiation causing
ionization of said atmosphere, a tube having a
control electrode and two principal electrodes.
said control electrode being connected to one off
the first-mentioned electrodes, an impedance in- '
terconnecting said control electrode with one of
of said principal electrodes, said other of said
principal electrodes being connected to the other
of said ñrst-mentioned pair of electrodes, and
current-indicating means responsive to current
flow between said principal electrodes.
11. In combination, a gas-tight tube including
a gaseous atmosphere and a pair of discharge
electrodes, one of said electrodes being a sub~
stance chosen from the group comprising uranium
and thorium, a tube having a control electrode
and two principal electrodes, said control eleo
trode being connected to one of the first-men
tioned electrodes, an impedance interconnecting
said control electrode with one of said principal
electrodes, a second impedance and a source of
direct-current voltage interconnecting said one
of said principal electrodes to the other of said
principal electrodes, said other of said principal
electrodes being connected to the other of said
first-mentioned pair of electrodes, and current
indicating means responsive to current ñow be
tween said principal electrodes.
WILLIAM E. SHOUPP.
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