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.