US2305452A - Method and device for depicting the intensity distribution in a beam of slow neutrons - Google Patents

Method and device for depicting the intensity distribution in a beam of slow neutrons Download PDF

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US2305452A
US2305452A US358938A US35893840A US2305452A US 2305452 A US2305452 A US 2305452A US 358938 A US358938 A US 358938A US 35893840 A US35893840 A US 35893840A US 2305452 A US2305452 A US 2305452A
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neutrons
neutron
image converter
source
depicting
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Kallmann Hartmut Israel
Kuhn Ernst
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N23/00—Investigating or analysing materials by the use of wave or particle radiation, e.g. X-rays or neutrons, not covered by groups G01N3/00 – G01N17/00, G01N21/00 or G01N22/00
    • G01N23/02—Investigating or analysing materials by the use of wave or particle radiation, e.g. X-rays or neutrons, not covered by groups G01N3/00 – G01N17/00, G01N21/00 or G01N22/00 by transmitting the radiation through the material
    • G01N23/04—Investigating or analysing materials by the use of wave or particle radiation, e.g. X-rays or neutrons, not covered by groups G01N3/00 – G01N17/00, G01N21/00 or G01N22/00 by transmitting the radiation through the material and forming images of the material
    • G01N23/05—Investigating or analysing materials by the use of wave or particle radiation, e.g. X-rays or neutrons, not covered by groups G01N3/00 – G01N17/00, G01N21/00 or G01N22/00 by transmitting the radiation through the material and forming images of the material using neutrons
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N23/00—Investigating or analysing materials by the use of wave or particle radiation, e.g. X-rays or neutrons, not covered by groups G01N3/00 – G01N17/00, G01N21/00 or G01N22/00
    • G01N23/02—Investigating or analysing materials by the use of wave or particle radiation, e.g. X-rays or neutrons, not covered by groups G01N3/00 – G01N17/00, G01N21/00 or G01N22/00 by transmitting the radiation through the material
    • G01N23/06—Investigating or analysing materials by the use of wave or particle radiation, e.g. X-rays or neutrons, not covered by groups G01N3/00 – G01N17/00, G01N21/00 or G01N22/00 by transmitting the radiation through the material and measuring the absorption
    • G01N23/09—Investigating or analysing materials by the use of wave or particle radiation, e.g. X-rays or neutrons, not covered by groups G01N3/00 – G01N17/00, G01N21/00 or G01N22/00 by transmitting the radiation through the material and measuring the absorption the radiation being neutrons

Definitions

  • a sepration of the slow neutrons from the quick neu ons involves the intermittent production of the eutrons, the intervals of neutron production be- .g comparatively briei'.
  • the source of neutrons At agreater distance cm the source of neutrons, a spatial separation the quick neutrons from the desired slow neuons then takes place.
  • the depicting. is carried out at such a place it by means or a device the operation of which nnot be timely influenced, but rather by means a neutron image converter according to the ct t the source of neutrons works only durshort intervals of time.
  • the quick neutrons first an then the slow neutrons upon a ctlon layer of this image converter, in [oh l the impinging neutrons produce l icles or gs. rays, which are used 1' the production or the fluorescent Il'd lien:
  • the quick neutrons and the gamma rays act, however. if only in a very slight measure, also directly upon the fluorescent screen or upon the photographic plate. As during the time when these quick neutrons and gamma rays pass through the image converter this converter is inomrati'le to accelerate electrons, its intensifying eflect is suppressed for these quick neutrons and gamma rays, so that the remaining direct effect of the quick neutrons and gamma rays upon the fluorescent screen or upon the photographic layer does not become disturbingly perceivable.
  • the neutrons of different speed pass successively through the converter.
  • the upper limit of the speed of the nutronsat a certaln adjusting of the phase shifting between the end of the production of neutrons and the starting of the neutron image converter is given by the distance of the image converter from the source of neutrons. The greater the distance of the neutron image converter from the source of neutrons is, thelower is at given phase shifting'the upper limit oi the speed of the neutrons coming into eflect.
  • Fig. 1 is a schematic sectional view, taken views illustrating two furthernwdiiications oi the apparatus of Fig. 1.
  • the ion beam I produced in the discharge tube impinges on a substance 2, for instance lithium, in which quick neutrons are produced, which are slowed down by the surrounding medium i, such as water.
  • the slow neutrons pass through the water-free aperture at t.
  • Quicker neutrons pass, but with less intensity, through the same aperture.
  • two diaphragms h and t are provided, of which the one, for instance 0, serves for the absorption of slow neutrons, whereas the other diaphragm t absorbs the X-ray radiation.
  • the beam l contains slow and quick neutrons which, in the diagrammatic illustration, are designated by and l i.
  • the layer 20 which consists, for instance, of lithium, heavy charged particles are released by the impinging slow neutrons of ray bundle l,
  • the controlling of the operating voltage of the neutron image converter and of the source of neutrons takes place in such a rhythm, that the undesired quicker neutrons it have already left the image converter when the latter is put into operation.
  • This is attained, in the constructional example shown in Fig. 1, in that the neutron image converter i0 is set into operation only a certain time after the cessation of production of neutron rays.
  • the two switche ll, 25 that are connected together by a common actuating device it are used for this purpose.
  • the switching in and out of the source of ions with the aid of switch I! is accomplished as follows:
  • the ions formed in the space between the anode l2 and the cathode It are collected into a beam by the shape of the anode it, this beam passing through the opening of the electrode it ascents and being accelerated by the potential V: maintained between this electrode and electrode It. They enter into the tube of electrode i5 in the direction of arrow I with great speed and impinge at its lower end on a substance 2--for instance, lithium-in which quick neutrons are produced by the impinging ions.
  • the electrodes it, It and It are separated from each other by the insulators it, iii.
  • the adjustment of the period of the production of neutrons and the time difierence between the switching out the neutron ray production and the starting of the neutron image converter is accomplished in a simple way by shifting the contacts of the switches ll, 26 and regulating the speed of the coupling device It.
  • the duration of the neutron ray production to be adjusted and the time differential between the switching-out of the neutron ray production and the starting of the neutron image converter is obtained in a simple manner from the times which are required by the desired slow neutrons to pass through the distance A, and which the slowest of the undesired quicker neutrons require for passing along the distance B.
  • the eflect of the gamma rays is not intensified according to this method by the neutron image converter.
  • the neutron image converter In a similar manner as the neutrons of undesired speed belonging to the beam I are prevented from acting on the image converter the undesired quick neutrons proceeding from the remaining portion of the device are separated out.
  • the source of neutrons can be switched in again as soon as the last of the desired slow neutrons hrve acted in the image converter.
  • the quick neutrons and the gamma rays have an extraordinarily high speed, so that they pass alon the distance A in a very short time, the image converter must be cut out before the production of the neutrons begins again, in order that it is inoperative when the first gamma rays oi the succeeding series reachit.
  • the controlling of the source of neutrons and of the image converter is preferably carried out periodically, in order to obtain a summation of the eflects.
  • the coupling of the engaging and disengaging means of the source of neutrons is preferably carried out electrically or mechanically in a manner known per se.
  • a periodical voltage of similar frequency can, for instance, be fed to the source of neutrons and to the neutron image converter.
  • the service voltage of the image converter must lag behind the service voltage of the source of neutrons.
  • the periodic control of the source of neutrons and of the image converter can be accomplished by the coupling device it Figure 1 or for instance by the arrangement shown in Fig. 2.
  • two pairs oi contacts for instance slip-brushes it, it are connected together periodically by segments of conducting material til, as that are embedded in disks 3d, 3! of insulating material while the disks are turned by a common shaft 32.
  • the length oi the conducting segments 2? and 29 and the relative position of these segments in relation to each other and the spacing of the contacts of the two pairs 26, 28 from each other and their relative position can be adjusted easily so that the desired switching sequence can be adhered to.
  • the distance of the image transformer from the source of neutrons is about 2 to 3 metres, and if the object is merely to separate out the quick neutrons from the slow neutrons and from those of median speed, it is advisable to put into service the source of neutrons every time for about A 0 second. this time to pass through the distance A of 2 to 3 metres.
  • the neutron image converter is put into operation. so that the neutrons of desired speed come into action successively.
  • this converter is put out of operation and the source of neutrons is put into operation again. In this example all slow neutrons must have passed through the distance A before the source of neutrons is switched in again.
  • the service frequency of the source of neutrons and of the image con verter amounts therefore to about 500 oscil lations per second, i. e., 500 Hertz.
  • a mechanically actuated diaphragm liberating the observation path with the frequency of the image converter can be provided, for instance in the ray path of an optical system producing a real or virtual image of the fluorescent screen.
  • the fluorescent screen is can be reproduced actually on a screen or on a photographic plate 35 by means of an optical system 33, 33.
  • a rotating disk 35 for instance is provided that has one or more openings it that free the beam path periodically when the disk rotates on the shaft 38.
  • Fig. 2 When an arrangement according to Fig. 2 is employed for controlling the source of neutron rays and the neutron image converter, it is advisable to couple the shafts it and 32 to each other directly. It is then possible in a very simple way to couple the periodic sequence of the switching in and out of the source of neutron rays and of the neutron image converter with the freeing oi the beam path for producing the picture on the screen 35.
  • the same arrangement can be used when, with the aid of the optical system it, ti l not a real but a? virtual picture is produced, that can be examined with the eye.
  • a corresponding device may also be used in the photo graphic depicting of the fluorescent screen image, provided that the fluorescent screen is not arranged in direct neighbourhood of the photographic layer.
  • the beam of ions may be deflected or the substance capable of emitting neutrons may be removed from the path of the beam of ions.
  • the deflection of the beam of ions may be efiected in the usual manner by electric or magnetic means or mechanically.
  • the removing of the substance capable of emitting neutrons is attained in the simplest manner by rotation of a body, the parts of which coated with a substance capable of emitting neutrons are actually brought into the path of the beam of ions'only during the times when the sources of neutrons has to operate.
  • the ion beam i as shown in diagram in Fig. 4 is deflected by a magnetic field so that temporarily it does not impinge on the substance 2.
  • a magnet coil 3% placed preferably outside the tube i5, this coil being fed by the battery V5 as long as the contact dd is closed.
  • the contact iii can be switched in and out in the manner presented in the explanation of Fig. l, by a coupling device id, the left part of which is'shown in Fig. 4.
  • the ion beam 5 is deflected so that it impinges on the wall at and therefore cannot release quick neutrons from the substance 2. Since in this constructional example likewise the production of neutrons must be interrupted during operation of the neutron image converter. the contacts to and 25 must be closed simultaneously so that the magnet coil 39 is energized only during the time of operation of the neutron image converter. Instead of the magnet field, an electrical field could likewise be used for deflecting the ion beam, this being controlled in analogous manner.
  • the periodical interruption of neutron ray production could likewise be accomplished by temporarily removing the substance capable of emitting neutrons from the path of the ion beam.
  • Fig. 5 shows a constructional example of an arrangement of this kind.
  • the electrode it of the discharge tube for producing quick neutrons is shown, and at the lower end of this electrode, on the rotating rod at, an application of the material 2 is made'at one or more places.
  • the rotation of therod 32 on the shaft 33 can be accomplished by electric motors arranged inside the receptacle for the production of neutron rays or, as shown in Fig. 5, by magnetic action through the receptacle walls.
  • the rod t2 consists preferably of a magnetic material, for instance iron, while the wall of the apparatus for producing neutrons consists of a non-magnetic materiai, so that the rod B2 is set into rotation under the influence of the magnetic field of the magnet rod t5 rotating outside the receptacle on the shaft Qt.
  • a sufllciently strong magnet rod it is possible to keep the slip tribution in a beam of which comprises producing between the movements of the rods i2 and ts so small that an exact adjustment of the time at which the ion beam impinges on the layer 2' and leaves it again is possible.
  • the shaft M can likewise be coupled to the shaft 32 or the coupling device i8 in the manner described in connection with the other constructional examples, so that the substance Zcapable of emitting neutrons is brought into the path of the ion beam temporarily only during the desired times of operation of the source of neutron rays.
  • a special advantage of the arrangement according to the invention is, that the photographic plate or the fluorescent screen, although they are at rest, are not exposed to the action of neutrons of undesired speed.
  • a method for depicting the intensity distribution in a beam of slow neutrons produced by impinging a beam of ions upon a substance capable of emitting neutrons which beam of slow neutrons contains also a radiation of larger speed, especially for the depicting of objects which comprises producing the neutrons intermittently, carrying out the depicting of the intensity distribution by means of a neutron image converter provided at a place at which the slow neutrons and the radiation of larger speed W9 ing to the intermittent operating or the source of neutrons are spatially separated the one from the other by their difference in moving-time, and
  • Apparatus for depicting the intensity distribution in a beam of slow neutrons, especially for the depicting of objects which comprises an ion source; a neutron source adapted to emit neutrons upon impingement thereon of ions from a said ion source, a neutron image converter in operative alignment with said neutron source but spatially removed therefrom at a preselected distance of the order of a few meters, said neutron image converter being adapted to be operated intermittently; means for depicting an observation ray from said neutron image converter; and means for interrupting emission of neutrons from said neutron source whenever the neutron image converter is being operated and for interrupting operation of the neutron image converter whenever neutrons of undesired speed are passing through the same.
  • Apparatus for depicting the intensity distribution in a beam of slow neutrons, especially for the depicting of objects which comprises an ion source; a neutron source adapted to emit neutrons upon impingement thereon of ions from said ion source, a neutron image converter in operative alignmentwith said neutron source but.
  • said neutron image converter being adapted to be operated intermittently; means for depicting an observation ray from said neutron image converter; and means for interrupting emission of neutrons from said neutron source whenever the neutron image converter is being operated and for interrupting operation of the neutron image converter whenever neutrons of undesired speed are passing through the same, said last named means including means for intermittently deflecting a beam of ions passing from said ion source to said neutron source.
  • Apparatus for depicting the intensity distribution in a beam of slow neutrons, especially for the depicting of objects which comprises an ion source; a neutron source adapted to emit I neutrons upon impingement thereon of ions from said i source, a neutron image converter in oper ive alignment with said neutron source but spatially removed therefrom at a preselected distance of the order of a few meters, said neutron image converter being adapted to be operated intermittently; means for depicting an observation ray from said neutron image converter; and means for interrupting emission of neutrons from said neutron source whenever the neutron image converter is being operated and for interrupting asooaoa oneration oi the neutron image converter vvhenever neutrons oi' undesired speed are passing through the same, said last named means ineluding means for intermittently moving said neutron source out of range oi a beam of ions from said ion source.
  • Apparatus for depicting the intensity distribution in a beam of slow neutronsespecially tor the depicting of objects which comprises an ion source; a neutron source adapted to emit 1 neutrons upon impingement thereon of ions from said ion source, a neutron image converter in operative alignment with said neutron source tout spatially removed therefrom at a preselected distance oi the order or a few meters, said new tron image converter being adapted to be operated intettently; means for depicting an ohsired speed are passing through the same.
  • said means including an optical system, in the ray path from the neutron image converter, for producing a visual image of the intensity distribution, a diaphragm in the ray path between said neutron image converter and said optical system and means for moving the diaphragm into and out of ray-obstructing position at the frequency of operation of the neutron image converter; and means for interrupting emission of neutrons from said neutron source whenever the neutron image converter is being operated and for interrupting operation of theneutronimage converter whenever neutrons of unde- Yll Q

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US358938A 1939-09-28 1940-09-28 Method and device for depicting the intensity distribution in a beam of slow neutrons Expired - Lifetime US2305452A (en)

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Cited By (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2525832A (en) * 1946-02-20 1950-10-17 Sheldon Edward Emanuel Tube with composite photocathode for conversion and intensification of x-ray images
US2549176A (en) * 1947-05-31 1951-04-17 Texas Co Detection of scattered neutrons
US2550106A (en) * 1947-06-06 1951-04-24 Westinghouse Electric Corp Detector for elementary particles
US2608661A (en) * 1945-10-16 1952-08-26 Walter H Zinn Means for measuring radiation
US2666864A (en) * 1950-01-20 1954-01-19 Westinghouse Electric Corp Image intensifier tube
US2690516A (en) * 1948-03-09 1954-09-28 Shcldon Edward Emanuel Method and device for producing neutron images
US2761084A (en) * 1949-03-30 1956-08-28 Sheldon Edward Emanuel Device for intensifying images of invisible radiation
US2853619A (en) * 1951-08-16 1958-09-23 Westinghouse Electric Corp Image amplifier phototimer
US3067329A (en) * 1959-03-12 1962-12-04 Fairchild Camera Instr Co Neutron detector
US3519822A (en) * 1967-08-10 1970-07-07 Atomic Energy Commission Time of flight to kinetic energy converter for a nuclear particle spectrometer

Cited By (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2608661A (en) * 1945-10-16 1952-08-26 Walter H Zinn Means for measuring radiation
US2525832A (en) * 1946-02-20 1950-10-17 Sheldon Edward Emanuel Tube with composite photocathode for conversion and intensification of x-ray images
US2549176A (en) * 1947-05-31 1951-04-17 Texas Co Detection of scattered neutrons
US2550106A (en) * 1947-06-06 1951-04-24 Westinghouse Electric Corp Detector for elementary particles
US2690516A (en) * 1948-03-09 1954-09-28 Shcldon Edward Emanuel Method and device for producing neutron images
US2761084A (en) * 1949-03-30 1956-08-28 Sheldon Edward Emanuel Device for intensifying images of invisible radiation
US2666864A (en) * 1950-01-20 1954-01-19 Westinghouse Electric Corp Image intensifier tube
US2853619A (en) * 1951-08-16 1958-09-23 Westinghouse Electric Corp Image amplifier phototimer
US3067329A (en) * 1959-03-12 1962-12-04 Fairchild Camera Instr Co Neutron detector
US3519822A (en) * 1967-08-10 1970-07-07 Atomic Energy Commission Time of flight to kinetic energy converter for a nuclear particle spectrometer

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NL58644C (en))

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