US2666890A - Apparatus for testing geiger tubes - Google Patents

Description

Jan. 19, 1954 R. L. DE VOLL ET AL 2,666,890

APPARATUS FOR TESTING GEIGER TUBES Filed July 27, 1950 INVENTOR. N JOHN ON/A Q RALPH L DE VOL!- BY ATTORNEY Patented Jan. 19, 1954 UNITED STATES PATENT OFFICE APPARATUS FOR TESTING GEIGER TUBES Delaware Application July 27, 1950, Serial No. 176,236

23 Claims. 1

This invention relates to apparatus for testing Geiger tubes and more particularly to apparatus for determining the response characteristics of Geiger tubes. The invention is especially adapted to provide a permanent record of the response characteristics of a Geiger tube in a minimum period of time without damaging the tube or in any way affecting its future performance.

In general, a Geiger tube has a hollow metallic casing which serves as a cathode and an axially disposed wire which serves as an anode. The tube is filled with a gas which is ionized when a radioactive particle enters the tube. The electrons produced by the gas ionization flow to the anode and the positive ions flow to the cathode forming a current pulse. The number of pulses which are produced when a constant source of radioactivity is at a fixed position from a Geiger tube is dependent upon the voltage between the anode and cathode of the tube.

With relatively low voltages on the tube, small increases in voltage between the anode and cathode produce relatively large increases in the number of pulses from the Geiger tube. When the voltage difference between the anode and cathode reaches an intermediate value, a plateau is reached in which the number of pulses increases only slightly with further voltage increases. At higher voltages, a corona discharge takes place between the cathode and anode, causing the number of pulses through the tube to increase considerably with small increases in volttages. Corona discharges are undesirable since they permanently damage the tube and shorten its life considerably. They also produce an alteration in the response characteristic of the tube.

Since each Geiger tube has a different response characteristic, a permanent record of number of pulses vs. voltage must be obtained for each tube. Heretofore, such records have been obtained by manually varying the voltage between the anode and cathode in predetermined steps. The response of the tube at the predetermined voltages is determined by averaging the measurements obtained from a relatively large number of radioactive emanations. Manual control of the voltage prevents the voltage on the tube from ever rising into the corona discharge region but requires a long time to complete the test, sometimes a matter of hours.

Such attempts as have been made to plot the response characteristics of a tube while automatically varying the voltage on the tube have ended in failure because of the inability to determine for each tube will commence.

2 the exact voltage at which the corona discharge As a result, the voltage on a tube often rises into the corona discharge region before it is cut off.

This invention provides apparatus for automatically varying the voltage on a Geiger tube over the safe region of the tube and for cutting off the voltage on the tube before the inception of corona discharge. The invention also provides apparatus for determining the response characteristics of the tube at the different voltage levels and for providing a permanent record of such response characteristic. Thus, the response characteristic of a Geiger tube is automatically determined in a minimum period of time and without any damage to the tube.

An object of this invention is to provide apparatus for determining the response characteristic of a Geiger tube.

Another object is to provide apparatus of the above character for obtaining a permanent zegord of the response characteristic of a Geiger A further object is to provide apparatus of the above character for determining the response characteristic of a Geiger tube in a minimum period of time.

Still another object is to provide apparatus of the above character for automatically determining the response characteristic of a Geiger tube without damaging the tube or in any way afiecting its future performance.

A still further object is to provide apparatus of the above character for gradually varying the voltage on a Geiger tube and providing an indication of the tube response at the different voltage levels.

Another object is to provide apparatus for reducing the cost of Geiger tubes by providing a cheap and reliable test of the tube.

Other objects and advantages will be apparent from a detailed description of the invention and from the appended drawings and claims.

In the drawings:

Figure l is a schematic diagram of one embodiment of the invention; and

Figure 2 is a curve illustrating a typical response characteristic of a Geiger tube with increases in voltage on the tube.

In one embodiment of the invention, a Geiger tube, generally indicated at Ill, is provided. The tube has a conductive casing 12, which is filled with a suitable gas such as argon, and a conductive wire l4 axially disposed within the casing in insulated relationship to the casing. The

accaeo diode 28. A resistance 30 is provid-edbetween the cathode of the diode 25 and ground. The plate of the diode 20 is connected to the cathode of a diode 32 and to a resistance 34 and capaci; tance 36 in parallel, one side of theresistance 84 and capacitance 36 being grounded. The plate of the diode 32 is connected through a r esistance 38 to a resistance 40 and capacitance in carer: lel. One side of the resistance 40 and capacitance 42 is grounded.

The grid of a tube 44 is connected to the resistance 38 and is grounded through aresistance 46. The cathodeof the tube 44 is connected to the cathode of a tube 40 and to the plate of a tube50. Positive voltage from a suitable power supply, such as a battery 52, is supplied through a resistance 54 to the plate of the tube 44. In like manner, the grid of the tube 48 is grounded through a resistance 55 and is supplied with bias voltage by the movable arm 56 of a potentiometer 51, whichis connected between the negative terminal and the-grounded positive terminal of a suitable power supply, such as a battery 58. Positive voltage is supplied to the plate of the tube 40 through a resistance 59. The resistances 55 and 59 ,have values corresponding to the resistances 46 and 54, respectively.

The plates of the tubes 44 and 48 are connected to each other .through a network which includes resistances 60, 62, 64 and 06 in series. The resistances 00. and 62 are equal to the resistances 66 and 64, respectively. The resistances are supplied at the common terminal between the resistances 62 and 64 with negative voltage from a suitable power supply, such as a battery 61, the positive terminal of which is grounded. The grid'of a tube 68 is connected to the common terminal between the resistances 60 and 62 and the grid of a tube 10 to the com mon ,terminal between the resistances 64 and 66. The cathodes of the tubes are grounded. The plates of the tubes 68 and I are connected to one side of solenoids I2 and 14, respectively. The other side of each solenoid is connected to the positive terminal of the battery 52.

As previously stated, the cathodes of the tubes '44 and 48 are connected to the-plate of the tube 50. The grid of the tube 50 is grounded through a resistance 16 and is supplied through a resistance 18 with negative voltage from the battery 61. The cathode of the tube is connected to the battery 61 through a relatively high resistance '80.

The solenoids I2 and I4 act in opposite 'directions upon a clutch "82 which is provided with a pair of magnetic friction plates 83 and 04 at its extremities. .The clutch 82 is mounted on a shaft, 85 driven by a motor 06, which is connected to a master switch '81 and a power-supply 08. The clutch is positioned by a spring 89 havinga disc 90 which is adapted to rotate within a hollow cylinder 91 secured to the center of thefriction plate 84. The other end of thespring 80 is suitably secured to a wall 92. H

A A wheel QBQwhich'may be made from a materialsuch as rubber, is mounted on a shaft 00 ,ance I60 and the battery 52.

between the friction plates 84 and 86. The shaft also carries the movable arm 56 of the potentiometer 5'! as well as a pinion gear I00, a clutch plate I02, and a pinion gear I04. The gear I00 has a smaller diameter than the gear I04, which is loosely mounted on a shaft 98 in frictional contact with the clutch plate I02. 7 p

The pinion gears I00 and I04 in turn mesh with rack gears I06 and I03, respectively. The rack gear I06 carries at one end a stylus H0 and an outwardly extendingarm I I2 which may be adjustably positioned on the rack gear. The arm I I2 is adapted to engage the movable contact of a normally open switch II4 carried by the rack gear I08. *At its other end, the rack gear I06 carries an adjustable arm II6 which is adapted to engage the hiov'able contact of a normally open switch I'IB, the stationary contact of the switch II8 being grounded. A stop I is provided at the same end of the rack gear I08 as the switch IIj8 to limit the movement of the rack gear. I

The stylus I I0 contacts a sheet I22 of plotting paper, which is held in fixed position between brackets I24 and I26. The bracket I24 carries a rack gear I28, and a pinion gear I driven by a motor I32 meshes with therack gear. A sum I34 carries the pinion gear I30, the iam ic I6 or the potentiometer I 8 and a hand crank I36. The hand crank l36 is adapted to rot'ate the shaft I34 in an opposite direction to the rota on provided by the motor I32 so as to return the rack gear I28 to its starting position aft'rth'e response characteristic of a Geiger tube has been plotted onasheet I22. V

The motor I32 is connected in a serie's circuit which includes an alternating current :power supply I38, a switch I40, the motor mans 'a normally closed switch I42. A switch I44 is provided in parallel with the switch I42 andis adaptedto be closeclby a finger I45 on the bracket I24 when the brackets I24 and I 26fare returned to their zero position by the crank I36. A second finger I46 is also provided on the bracket I24 to open a switch M1 at the Zero-position of the brackets I 24 and I 26. i

The switch 2 I and a switch I48 are ganged tothe switch I42 and are operated by a solenoid I 50 connected at one end to the positive terminal of the battery 52 and at the other end to the movable contact of the switch I48. The movable contact of the switch I48 is also connected to the stationary contact of the switch l'l4, and the stationary contact of the switch I48 is connected to the stationary conact of the switch I41, the movable contact of whichis grounded.

A neon bulb I54 is connected between the movable contact of the switch I I8 and the stationary contact of a switch I56, the grounded movable contact of which is ganged to the switch I40. A capacitance I58 is provided in parallel with the switch H8 and in series with a resist- In addition to being connected to the neonbulb I54, the stationary contact of theswitch I56 is connectedto the grid of a tube I62. The grid of the tube I62 is grounded through a resistance I64 and the cathode through a resistance I66. Positive voltage from the battery 52 is supplied to the cathode through a resistance lfia and to the plate through a solenoid I10, The solenoid has an armature I12 witha dog I14 which is adapted to lock the rack gear I08 when the solenoid is energized.

As previously stated, the Geiger tube I0 is filled with gas molecules, such as argon. When a radioconverted into a rectangular shape by the active emanation penetrates the casing I2, it

causes some of the argon molecules to be ionized and electrons and positive ions to be formed. The electrons are attracted to the axial wire I4, which serves as the anode of the Geiger tube, and the positive ions are attracted to the cylinder I2, which serves as the cathode. As the electrons and positive ions move toward the anode and cathode, respectively, they strike other argon molecules and cause some of these molecules to be ionized. The number of argon molecules which are ionized is determined by the force of impact between the molecules and the ions, and this force is in turn dependent upon the voltage between the anode and cathode of the tube.

At low voltages, commonly designated as the threshold region of the Geiger tube response, small changes in voltage produce relatively large changes in the number of molecules which are ionized and which are attracted to the tube electrodes to produce current pulses through the tube. As the voltage increases, a plateau region is reached in which relatively large changes in voltage produce only small'changes in the number of pulses. As the voltage on the Geiger tube increases still further, a corona discharge takes place and produces spurious pulses which mask the true number of pulses produced by the radioactive emanations; As previously explained, corona discharges may permanently damage the tube or alter 'the'response characteristics of the tube at the difierent'voltage levels. The threshold, plateau'and corona discharge regions of a representative Geiger tube or illustrated by the portions I16, I18 and I80, respectively, of the curve shown in Figure 2. 1

We have found that the plateau region I18 begins at substantially the same voltage for each tube. We have also found that for most tubes the number of pulses at the end of the plateau region I18 exceeds the number of pulses at the beginning of the plateau region by approximately 20%. By measuring the increase in the number of'pulses from the beginning of the plateau region and cutting" off the voltage supplied to the tube when the pulse increase is slightly less than 20%, weare able to provide an indication, without damagingithe tube, of the response characteristic of the tube over its complete operating range.

We provide an indication of thevolta'ge on the tube at any instant by simultaneously varying the positions of the potentiometer arm I8 and the sheet I22 The positions "of the potentiometer arm I8 and the sheet I22 are simultaneously variedwhen the switch I40 is manually closed, causing the motor I32 tobe'operated through a circuit which includes the power supply I38, the-switch I40, the motor I32 and the normally closed switch I42. As the arm I5 rotates around the potentiometer I8 to increase the voltage on the Geiger tube at a constant rate, the rack gear I28 moves the sheet to the left in Figure 1. Thus, the sheet can be calibrated along a horizontal axis to provide at any. instant an indication ofthevoltage on the Geiger tube.v When a radioactive emanation penetrates the tube, acurrent pulse having a shape illustrated in. curve I82 and an amplitude determined by the voltage on the tube flows through the tube. The pulse is amplified by the amplifier 22 and multivibrator, as illustrated in curve I8 4. Each negative pulse from the multivibrator produces a negative pulse on the cathode of the tube 28 and causes current to flow through the capacitance 35,-the diode 28 and the resistance 38. The current charges the capacitance 38, which dischargesthrough the resistance 34 during the intervals between pulses. Because of the large time constant provided by the resistance 34 and the capacitance 38, the capacitance is generally unable to discharge completely during the intervals between pulses; and a voltage proportional to the number of pulses fromthe Geiger tube I0 builds up across the capacitance 36 The tube 32, resistance 40 and capacitance 42 provide a further smoothing action to the voltage across the capacitance 36.

The voltage across the capacitance 42 biases the grid of the tube 44 and the voltage on the arm 56 of the potentiometer 51 biases the grid of the tube 48. Since the cathodes of the tubes 44 and 48 are connected to the plate of the tube 50, the plate currents through the tubes 44 and 48 flow through the tube 50. The sum of the two plate currents always remains substantially constant since the high value of the cathode resistance 80 prevents the current flowing through the tube 58 from changing materially.

If the bias voltages on the grids of the tubes 44 and 48 are equal, the currents through the tubes are equal, producing similar biases on the grids of the tubes 58 and 'Ill. The equal grid biases on the tubes 68 and 1a in turn cause equal currents to flow through the solenoids I2 and I4. Since the solenoids I2 and I4 act with equal force but in opposite directions on the clutch 82, the clutch is not moved in either direction into engagement with the wheel 96. The gears I80 and Hi4 therefore remain stationary and the stylus Ill] continues to maintain its same vertical position relative to the sheet I22.

If the number. of pulses from the Geiger tube I8 increases,.the bias on the grid of the tube 44 becomesmore negative than the bias on the grid of the tube 48, and the plate currents through the two tubes of each stage become unequal. The unequal plate currents cause the grid bias on the tube 68 to be less negative than the bias on the tube I8 and the current through the solenoid I2 to be greater than the current through the solenoid I4. The solenoid I2 therefore actuates the clutch 82, causing the friction plate 84 to engage the wheel 96. With the motor 88 operating after the closure of the switch 81, the wheel 96 drives the gears I88 and I84 in a direction to move the stylus upwardly in Figure 1 so as to provide an indication of the increased response of the Geiger tube. At the same time, the wheel 96 drives the potentiometer arm 56 in a direction to increase the negative bias on the grid of the tube 48. This causes the bias on the tubes 44 and 48 to become equal at the stylus position corresponding to the number of pulses from the Geiger tube. Similarly, when the number of pulses from the Geiger tube decreases,

the stylus moves downwardly and the potentiometer arm 58 moves in a direction to reduce the negative bias on the tube 48.

When the stylus III! starts to move along the verticalco-ordinate of the sheet I22 from its zero position, the rack gear I88 removes the short circuit acros the capacitancel58 by releasing the movable contact of the switch H8. The capacitance I58 is charged by the battery 52 and, after a predetermined delay dependent upon the time constant of the resistance I58 and the capacitance I58, a sufficient voltage is produced across the capacitance to break down the neon ulb: Wt hen; he una list ccnuuctst t: arc:-

a ked; t at olt ge co r s ondi to; the egins when; the plateau region it 1118:; of, thefieieer tu e es onse c a ac rist c tl imcl a l he rack gear 10 islo lked he 19%} I y t; hastmcv dq hr u h a d stance which is approximately 2Q% greater than, the distgg ce agluanced bv therack gear I116. As; the number ihuls sl rqm e Geiger, u e cr ascs. thef ach fiar I 6- dvanccs cw ds. thelrack spear ll}! Ijhe rack gear 10,6, overtakeslthewrackflgear '08: t h end; i. he. l teau, e ion, since, e number of l e s, th n annrox matelt 20%: gre er han he numbe fnulses at hegbcgin nine ct the; p ateauregiom When he ack sear l0t,overtakes,the ackigear 1 8 he arm H2, on the ashv ge r loses the switch tthenchx providin a ontinuous c rcuit-tot the s lencid, fifip, ihc/ clc cisi, it ne ate t ;intc rupt hei unnly cflvc taeic o hem.- cntiometcr 8 and to, thelmctcr lilgbyh penine the itch s. M a t I pe tive y," A h ld n circuit, for the solenoidh inclu ing. he. attcrx 2; he; o ncii. 50.. he, witch :48;. and, t e switch .1 t also provided; y h c vicsinel of; h sw ch me: The w tchfll isl l sedm at t inst ntthat he brackets L2 1 and, 12.6 are, moved; to he ft fr m heir startin p i i n.

The switch Mil-is...v m nuallr, ned" and he switc 56. manual y, osed. hcfcrc. th ach ge r I28 d hew rac tcts itand; fia er turned to their starth efln sit c sl o cn nec i h sw t I40. prevents he. moto 'fl't rc in nopcrated evcnthcueh the sw tc 2: ma c ose nndc csurc 0,11 thekswiteh lilieauses the dog I14 to be released; from. heacke ar. 1. n e, u nt no on er. l wsl hr u h hs c id and he tube [621, Upon thcrelease of the, dog PM, ,A the rack gear I'08 is,,free to move with-.thegrack; gear Lotto its startin po tion, h eturn moveme t 01113116 rap}; gears lot ancl liltiitakes place because thefvolt'age on the gridcfflthetuhe 4821s more negative". than the voltage on the grid' of" the tube .ld' causing the solenoid 'L lf'to be energized. 'llh rack gears Dfiand;lt' 8-moy s mu ta eous to th ir. starting position hecause of the yslippage between. the; clutch. plate I02" and the pinion gear L04;

.At the sarne time thatthe rackgears I96" and I118; are returning to; their zero positions, the brackets 12,4 and 12:5 may he returned to their Starting positionby the manual operation of the handcranlg I36, When the brackets I24 and I25 reaqh their starting position, the finger M6 opens the switch M1,; causing the holding circuit through the solenoid 15p to .be broken; At't-he same time the finger I45. closes the switch M4 and prepares the motor L32:for-operation upon the closure o f the switchv I401, The; switch-j 81 is preferably opened fter thestylus llugreaches its z r apcsiticn mu vcn 1 ssi tit-scf themotor 85 being operated; The operatorthen removes; the. Geiger tube on which the test has heennmadei, and the sheet on, which the response haracte istic, has een p d an he inserts aln w. Geig r tube and. a ,fre h h p n paper before closing the switches M0 and 81.

The. apparatus disc os diahcvc a ver The', time:

a; cement-advantages ltqbtainslanltpermenenthe records the response characteristics 0i a Geigen tuhe, in-av.minimum. periodmf time, Sincelit op r e ut m tically it does. not requ e on: stant attention, anti one;semhskilledioperator can simultaneously, supervise the; testing of a several e e1; tubes. The: apparatus, also reduces to a. the number ofw-tubeslwhich are, darnagect durin the testing operation,sincev thelvpltagepn the tuhes very seldom .risesinto. the. corona ischarge region. a, result 7 at. the above. ad? vantages, the apparatusmay. be, instrumentallin materiallx reducing the. presently high costfof Geiger tubes.

In addition: to providing a,rclativelit n xll Sive test, the apparatus also provides a. reliable an i accurate, indication. of the Geiger tubes re, sponse characteristic. Because, of? thewcopti'lis uouslyl variable. voltage on." the, Geiger; tube" the number of, pulses, from thedtube, is, determined for; every voltage in the, operating region. instead of at discrete voltages, the, latter, being the methodv usedv when. thev response. characteristic i obtained. manualIy-. Furtl,iermcre, by. tain: his a cont nuous recc dation. on the. num e 01 pulse v vo a e, response. a... relativ r smcctn curve is obtained. and, this curve can beleasilyi'uterpretect, even by semiyskilled; personneli who may have occasion tcluse the tube,

Although this invention hasQb'eenmdisclbsediand llustrated with ref rencelt'o particular. applieae ticns. the. principles, involved are. susc p or num rou other. pplic tions. which .w ll "b aniparent tnper ons skilledilinthc art; The 'invenr tion is, therefore, to e. limite I only as indicated by the scope of the appendedli0laims Whatisclaimedls; -lA aratus for. destermin hsv the resp s characteristic oft aeGeiger tuhe, including means for; a lyin a continuously: varia e; vo e n the tube, means for; providlng an indication of the response of the tube. radioactive emanate tiQns, atlthel different voltage; 1evels, a n;dmeans responsive .to. a. pr determined output, fromthe tubeto breaklofiitlie supplyof voltage toithetutie. 2!. Apparatus for, d'eterminingthe response characteristics otafieiger tube, lncludingmeans for continuously; varying, the voltage; imposegi upon, the tube. means, for producing electrical pulses upon the penetration ofradioactivecma: nations: into ,the tube. means for determinihg g the number; of pulses. at, the different volta es-levels. and vineansifor, cutting ofltheyoltegelto the; tulie at! alpredeterm nedrpulse level; 3; Apparatus fon determining; the, response characteristics-0f: alGeiger-tube, including means for continuously varying the voltage on, the "tube, means for determining ythep resppnsenofi-the tub? to radioactivevemanationswithoifierent:voltages on the, tu;be;pmeans tor plottingga curvegof the uheircsponse at: thewicdifielienbrlVOltflgfiJBMBlSetO provide;atpermanentq record 30f; thetube-characateristi andqmeans operative. ate pred termined levekof (tube: resnonseirctoycuttoficfthe rvoltagclsttm tc-thetuhe; l 4. Apparatuss for determining; the: response characteristics oi s/Geiger tube,-;incl-uding%;ameans for providing the tube. witha ;,continuously able'level of energization; means for -providing an indication-cl the number of pulses: moducemim the tube uponthe introduction of radioactive emanations, means forproviding an indlcatlonwf the voltage at a which the different pulse levels occur: and means'operative to cut offlthe energy 9 supply to the tube after the number of pulses has reached a predetermined level.

5. Apparatus for determining the response characteristics of a Geiger tube, including, a first motor, a voltage supply means driven by the first motor for continuously varying the voltageintroduced by the voltage supply to the tube, means for determining the response of the tube at the different voltage levels, a second motor, first means driven by the second motor at a relatively high speed for a predetermined period of time, and second means driven by the second motor at a reduced speed in accordance with the determinations of counter response, the second driven means'being operative at a predetermined tube response to cut ofi the first motor and the voltage supply.

6. Apparatus for determining the response characteristics of a Geiger tube, including, a motor, voltage supply means, means driven by the motor to graduallyvary the voltage introduced by the supply means to the Geiger tube, means for determining the response characteristics of the Geiger tube at the difierent voltage levels, a second motor, means operative to activate the second motor in accordance with the determinations of tube response, and means driven by the second motor and operative at a predetermined level of tube response to cut off the voltage supply.

7. Apparatus for determining the response characteristics of a Geiger tube, including, a voltage supply having a variable output voltage, a motor, means driven by the motor for varying the voltage introduced to the Geiger tube, means for determining the response characteristics of the Geiger tube at the different voltage levels, indicating means upon which a permanent record of the response characteristics may be made, means for providing upon the indicating means a recordation of the tube response, means driven by the motor for varying the position of the indicating means in accordance with the rate of change in the voltage introduced to the tube, and means for cutting ofi the supply of voltage to the tube at a predetermined response level.

8. Apparatus for determining the response characteristics of a Geiger tube, including, a voltage supply having a variable output, means for varying at a predetermined rate. the voltage introduced from the voltage supply to the Geiger tube, means for providing an indication of the tube response at the different voltage levels, first means driven at a relatively high speed in accordance with the response of the Geiger tube, means for stopping the first driven means at the beginning of the plateau region of the tube response characteristic, and second means driven at a reduced speed in accordance with the response of the tube and operative upon the first driven means at the end of the plateau region to out off the supply of voltage to the Geiger tube.

9-. Apparatus for determining the response characteristics'of a Geiger tube, including, a voltage supply having a=variable output, means for varying at a predetermined rate the voltage introduced from the voltage supply to the Geiger tube, means for providing an indication of the tube response at the different voltage levels,

means positioned in accordance with the response characteristics of the tube, and means for preparing the positioning means at the beginning of 'the plateau region'of the response characteristics to cut off the voltage" supply to the tube at the end of the plateau region.

'esponse at the different voltage levels, and

ieans operative at the end of the plateau region ,f the response characteristic to cut off the voltage supply and to stop the motor.

11. Apparatus for determining the response characteristics of a Geiger tube, including, a voltage supply having a variable output, means for varying at a predetermined rate the voltage introduced from the voltage supply to the Geiger tube, means for measuring the response of the tube to radioactive emanations at the different voltage levels, a motor, a first rack gear adapted to be driven by the motor at a relatively high speed in accordance with the response of the Geiger tube, means for stopping the first rack gear at a voltage on the Geiger tube corresponding to the beginning of the plateau region of the tube'response characteristic, a second rack gear adapted to be driven by the motor at a reduced speed in accordance with the response of the Geiger tube, means carried by the second rack gear for recording the response of the tube to radioactive emanations, and means operative by the second rack gear upon a predetermined movement of the second gear relative to the first gear after the stoppage of the first gear to cut off the supply of voltage to the Geiger tube.

12. Apparatus for determining the response characteristics of a Geiger tube, including, a voltage supply having a variable output, means for varying at a predetermined rate the voltage introduced from the voltage supply to the Geiger tube, means for measuring the response of the tube to radioactive emanations at th difierent voltage levels, means for providing a recordation of the tube response at the difierent voltage levels, a motor, a reversible clutch operatively coupled to the motor for movement in a direction to compensate for any difference between the .measurement of tube response and the actual value recorded, a first rack gear adapted to. be driven by the clutch at a predetermined speed, a second rack gear adapted to be driven by the clutch at a predetermined speed less than that of the first gear to create a difierential of movement between the two gears, means for stopping the first gear at a voltage onthe Geiger tube corresponding to the beginning of the plateau region of the tube response, and means carried by the second-gear for interrupting the supply of voltage to thetube upon a predetermined movement ;-of the second gear towards the first gear after the stoppage ofthe first gear. 1 j '13. Apparatus for determining the response characteristics of a'Geiger tube,.including, a, voltage supply having a variableoutput, means for varying at a predetermined rate the voltage introduced from th voltage supply to the Geiger tube, means for measuring the response of the tube to radioactive einanations at-the different voltage levels, means for providinga recordation of the tube response at the different voltage levels, a motor, and means, including a reversible clutch, operatively coupled to th motor to vary vthe positioning of the recording? means so as to iable voltage supply connecteditothe iGeigerttube,

a :motor operative to ;continuously the voltage applied by the voltage. supply 7'60 the-Geiger tube, means 'forzmeasuring the response of the .iGeiger tube tOJradiQaotive:emanations atwthetdif- :Ierent voltage levels, a afirst :rack :gear zadapted "to F 'be driven r at a predetermined speed in :accordance with the response :ro'f :the Geiger tube :to :r-adioactive emanationsxa secondraok gearaadapted'to :be driven rat :a predator-"mined:speedless't-han that of the .first gear in accordance with th :response ':of the Geiger tube to radioactive emanations, means connected to the second rack gear to ;retcord the :movements of the gear, :means for :stopring the rfirst :rack gear at the beginning of the plateau, region .OfathGiGEigBr tube :response,:means rifor bontinuing :thez-movemont of the second track gear until :it reaches thelfirst gea-r at a predator,- :mined position tin the plateau .regioneand means iforcuttingpif thesupplyof voltage to rthe'Geiger tube when the; second gearareaches the first gear.

15. Apparatus for determining the response -;characteristios of a Geiger atube, including a first i'motor, means operative \by ,the motor -.to "apply a :continuously variable voltage :to the Geiger xtube, indicating ,means (continuously movable along "a first axis in accordance with the ehangedn voltage applied to the-Geiger ,tubze, means .for meas- .uring the response 'of the Geiger tube vto radioactive lemanations which penetrate the tube ,at

0nd motor, va 'olutch .adapted to berdriven ,bythe ,motor in one direction -f0r Geiger tuberesponses of increasing intensity and in the other direction .:for Geiger tube responses of decreasing intensity, a first ,rack gear adapted to be driven by the clutch in :a direction perpendicular to the lfirst axis, a second-rackggear adapted to be driven by theclutch in the same -,direction as the first ,rack gear but at a predetermined speed lower than ,the first gear, means on the second gear for recording ,the movements .of the gear, means for stopping the first gear at a position correspond- ;ing .to the beginning of the plateau region of lGeiger tube response, .and means for stopping ,the second .gear .and cutting off the supply of voltage to the Geiger tube upon a predetermined .movement of the second gear relative to the first ,gear after the firstgearhasbeen stopped.

16. Apparatus for determining the response characteristics of a Geiger tube, including, a first motor, a reversible clutch adapted to be driven "by the motor, means for actuating the clutch in accordance with "the response of the Geiger tube toiradioactive emanations penetratingth tube, a first rack 'gearadapted to be driven by the clutch, 'a second rack gear adapted to "be driven by the 'elutc'hat'a predetermined speed-less than the-first rack gear, means carried by' the'secon'd rack gear for recording "the movement of the gear, indicating means responsive to the movement of the f recording means, means operative in accordance with the "differential of movem'ent between the first and secon-d'rack gears to stop the movement of the gears at a substantially predetermined position :in the response characteristics of the :Ge'iger tube, means for varying in .a predeter- :mined manner :the voltage applied to thefieiger :means for varying the position oftheindlmating means relative :to the recording means in :accordancev with the change in voltage applied 1 'ftoi'the Geiger tube and inracdinectioniperpendmnthe iGeiger tube, :means for producing a first control voltage proportionate to the response .01 the tube, a shaft, means mounted on :the shaft :for producing a second control voltage variable with the :rotation of the shaft, a motor, ,a reversible clutch adapted to be driven by the motor in :a idirection :determined iby the relative values 'of the first and second control voltages and to drivezthe shaft :in avdirection ato reducethe disparity zbetween the :first and "second control voltages, and

uneans positioned in accordance with "the movement of ithe=shaft to 'provide an indication :0: the response sof ithe tube.

.-1:8. Apparatus lior determining the response characteristics of a :Geiger tube, including, means for applying Ea continuously variable voltage-to the Geiger :tube, means1 for producing 19, first con- ;trol voltage proportionate to, {the response-of rthc Geiger tubeito radioactiveemanations,Fmeans for producing a :second :control voltage, a pair ro'f rsolenoids responsive to any differences between the first and second control voltages, ,a reversible ,friction =clutch operative :acoordanee with any difference in energization between, (the two solenoids and in .a direction determined by the'solenoid having thelgreater ,energizationsmeansoper- 'ative :by the clutch to vary the lsecondicontrol voltage in 1a direction to :reduce :any difference ;'between the first :and seoondhontrol voltages, z-and means operative by itheaclutch itoprouide an incli- -cation of thersecond control voltage.

19. Apparatus l-for determining the lrespons characteristics of a Geiger itube, including, ,means for applying a eontinuously variable voltage to the Geiger tube, means ior producingia =firstoontrol voltage proportionate to the :responae of the Geiger tube to radioactive omanations, means-cor producing a second control voltage, .a pair of solenoids :responsive to any difierences between the firstand second control voltages, a reversible jriction clutch operative in accordance ony difference in energization between ,the twoisole- .noidstand :in :a direction determined by the solemoid having"the-greater energization, means open- .ative by the clutch to vary the second control voltage vin a direction to reduce any difterence between the first and second control voltages, ;mcans,operatiueby ,the-clutchto provide unwindihationyof the "second control voltage, and means Ker-cutting off the soltage applied. to the Geiger tube rafter theisecond control voltage hasreac'hcd :a value corresponding to ,a pnedetennined Geiger tube response.

20. Apparatus ifor determining the response characteristics of a- Geiger tube, including, .means for applying a "continuously variable voltage to the Geiger tube, means tor producing a fitstcon- ,trol voltage proportionate to the response-oi the Geiger tube to radioactive :ema-nations, means :ior producing a second control voltage, .a first solenoid energized in accordance with the 'first control voltage, a second solenoid energized in ac- :cordance wlith the secondcontrol voltage. a um- ,neticlfriction actuated direction by the first solenoid and Juan ,npl iosite :direction by the second solenoid, meansaengaged by the clutoh for movement in one direction when the energizane@ clutph, a pair of solenoids operative in oppotion of the first solenoid exceeds the energization of the second solenoid and for movement in an opposite direction when the energization of the second solenoid exceeds the energization of the first solenoid, means operative by the movement of the clutch to vary the second control voltage in a direction to reduce any differences between the first and second control voltages, means for recording the value of the second control voltage with respect to the variable voltage applied to the Geiger tube, and means for cutting off the voltage applied to the Geiger tube after the second control voltage has reached a value corresponding to a predetermined Geiger tube response.

21. Apparatus for determining the response characteristics of a Geiger tube, including, means for applying a continuously variable voltage to the Geiger tube, indicating means, means operative upon the indicating means to provide a record of its position, means for adjusting the position of the indicating means relative to the recording means along a first axis in accordance with changes in the voltage applied to the tube, means for producing a first control voltage proportionate to the response of the Geiger tube to radioactive emanations penetrating the tube, means for producing a second control voltage proportionate to the position of the recording means relative to the indicating means along a second axis substantially perpendicular to the first axis, and means for adjusting the position of the recording means relative to the indicating means along the second axis so as to eliminate any differences between the first and second control voltages.

22. Apparatus for determining the response characteristics of a Geiger tube, including, means for applyinga continuously variable voltage to the Geiger tube, indicating means, means operative upon the indicating means to provide a record of its position, means for adjusting the position of the indicating means relative to the recording means along a first axis in accordance with changes'in the voltage applied to the tube, means for producing a first control voltage proportionate to the response of the Geiger tube to radioactive emanations penetrating the tube, means for producing a second control voltage proportionate to the position of the recording means relative to the indicating means along a second axis substantially perpendicular to the first axis, a reversible mag site directidnsupon the clutch in accordance with the values of the first an d second control voltages, and means operative Fyn nqement of the clutch to adjust the position of the re ording means in a direction along the second axis to e duce any difference between the first and second control voltages.

23. Apparatus for determining the response characteristics of a Geiger tube, including, means for applying a continuously variable Voltage to the Geiger tube, indicating means, means operative on the indicating means to provide a record of its position, means for adjusting the position of the indicating means relative to the recording means along a first axis in accordance with changes in the voltage applied to the tube, means for producing a first control voltage proportionate to the response of the Geiger tube to radioactive emanations penetrating the tube, means for producing a second control voltage proportionate to the position of the recording means relative to the indicating means along a second axis substantially perpendicular to the first axis, a reversible magnetic clutch, a pair of solenoids operative in opposite directions upon the clutch in accordance with the values of the first and second control voltages to produce a movement of the clutch dependent upon any unbalance in the control voltages, a first rack gear operative by the clutch for movement along the second axis, a second rack gear operative by the clutch for movement along the second axis at a predetermined speed less than the first gear, means for stopping the first gear upon the application of a predetermined voltage to the Geiger tube, and means for cutting off any voltage to the Geiger tube upon a prede termined movement of the second gear relative to the first gear after the discontinuance of movement of the first gear.

RALPH L. DE VOLL.

JOHN ONIA.

References Cited in the file of this patent Gibbs May 10, 1949

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