EP0441853B1 - Verfahren und vorrichtung zur bidimensionalen lokalisierung nichtgeladener partikel, insbesondere bei geringer zählrate - Google Patents

Verfahren und vorrichtung zur bidimensionalen lokalisierung nichtgeladener partikel, insbesondere bei geringer zählrate Download PDF

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Publication number
EP0441853B1
EP0441853B1 EP89912456A EP89912456A EP0441853B1 EP 0441853 B1 EP0441853 B1 EP 0441853B1 EP 89912456 A EP89912456 A EP 89912456A EP 89912456 A EP89912456 A EP 89912456A EP 0441853 B1 EP0441853 B1 EP 0441853B1
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EP
European Patent Office
Prior art keywords
converter
charges
particles
plane
neutral particles
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
Application number
EP89912456A
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English (en)
French (fr)
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EP0441853A1 (de
Inventor
Serge Maitrejean
Mario Ruscev
Irène Dorion
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Schlumberger SA
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Schlumberger SA
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Publication date
Priority claimed from FR8814187A external-priority patent/FR2638567B1/fr
Priority claimed from FR8814186A external-priority patent/FR2638536B1/fr
Application filed by Schlumberger SA filed Critical Schlumberger SA
Publication of EP0441853A1 publication Critical patent/EP0441853A1/de
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Publication of EP0441853B1 publication Critical patent/EP0441853B1/de
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J47/00—Tubes for determining the presence, intensity, density or energy of radiation or particles
    • H01J47/02—Ionisation chambers
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J47/00—Tubes for determining the presence, intensity, density or energy of radiation or particles
    • H01J47/12—Neutron detector tubes, e.g. BF3 tubes
    • H01J47/1205—Neutron detector tubes, e.g. BF3 tubes using nuclear reactions of the type (n, alpha) in solid materials, e.g. Boron-10 (n,alpha) Lithium-7, Lithium-6 (n, alpha)Hydrogen-3
    • H01J47/1211—Ionisation chambers

Definitions

  • the present invention further relates to a method for detecting and locating particles in a stream of neutral particles emitted by a source in such a device.
  • the object of the present invention is, on the contrary, to allow the production of higher resolution images and to allow, on a secondary basis, the obtaining of a high contrast, even in a priori unfavorable conditions of irradiation of the object to be examined, and more particularly in the event of poor conversion rates and / or in the presence of fluxes of incident particles of low intensity.
  • the device of the invention is essentially characterized in that said conversion elements capable of also ensuring the collection of charges consist of cells distributed in a flat two-dimensional matrix arranged beyond the anode wires with respect to the source .
  • the images obtained by the device of the invention have a higher resolution than that of the images obtained by the prior device described in patent EP-A-0 000 271, the two-dimensional matrix of which is formed by two parallel planes. linear elements also parallel to each other, the elements of two different planes being however crossed.
  • the converter comprises an insulating plate, one face of which carries said cells, this plate comprising, for each cell, a passage putting this cell in electrical contact with a conductor terminating on the other face of this plate.
  • the anode wires are placed in at least one plane substantially parallel to that of the converter, and are substantially parallel to each other.
  • the cells comprise a conversion material chosen from the group comprising gadolinium, boron, and lithium, in the case where the particles neutrals used are neutrons and the cells comprise a conversion material chosen from the group comprising iron, and silver in the case where the neutral particles used are X-rays, in particular soft X-rays.
  • the gas contains an extinguishing substance present in a proportion of at least 25 percent and that the ratio of the distance "S" between two neighboring anode wires, at the distance "G” between these wires and the converter, ie at least equal to 1.
  • At least one of the charge collection elements is connected to a reference electrical potential by means of a capacity capable of accumulating the charges collected by this element.
  • the device also comprises a source of voltage capable of creating an electrical voltage between the cathode and the anode wires at least equal to 2000 volts, and the anode wires have a minimum diameter greater than 20 microns.
  • the charge amplification operation preferably comprises the application of an electric field of sufficient value to allow the appearance of electronic avalanches of self-regulated size.
  • the method can advantageously comprise another operation, consisting in accumulating for a certain time the collected electrical charges.
  • the conversion of neutral particles into electrical charges is ensured with a conversion rate such that the number of particles detected is less than 105 particles per second and per square centimeter of surface of the converter.
  • FIG. 1 represents in 1 a source of neutral particles, for example a source of soft X-rays, but more typically a source of thermal neutrons in the main applications of the invention.
  • a source of neutral particles for example a source of soft X-rays, but more typically a source of thermal neutrons in the main applications of the invention.
  • At least part of the flow of particles emitted by this source passes through an object to be examined 2 and reaches the device 3 to which the present invention relates more particularly.
  • this device 3 firstly comprises an enclosure, intended to contain a gas and formed of a base 4a and a cover 4b made integral with each other so airtight vis-à-vis the atmosphere, the cover 4b being, however, permeable to neutral particles emitted by the source 1, to neutrons for example.
  • the gas contained in the enclosure is a gaseous mixture allowing the appearance of a "streamer" operating mode, in other words the appearance of avalanches of electrons whose size is self-regulated by spontaneous suffocation.
  • this gas comprises an effective quenching substance, consisting of carbonaceous and polyatomic molecules comprising many relaxation modes, such as isobutane or neopentane, in proportion of at least 25 percent.
  • this gas can be a mixture of 50 percent carbon dioxide and 50 percent isobutane, subjected to a pressure of the order of one to five bars.
  • the converter 5 and the planar grid are connected to a reference electrical potential, and are for example brought to potentials close to the earth potential prevailing outside the enclosure, both playing the role. cathodes.
  • the wires of the planar network 6 are on the other hand connected to an external source of electrical potential which delivers a positive potential + V with respect to the average potentials of the converter 5 and of the grid 7, for example of the order of 2000 to 7000 volts.
  • the converter 5 comprises an insulating plate 8, better visible in FIG. 3, and a two-dimensional matrix of cells, such as 9a, 9b, 9c, arranged on one face of the plate 8.
  • Each of the cells such as 9a, is intended to supply a signal representing a point of a two-dimensional image of the object 2.
  • Each of the cells therefore operates independently of its neighbors, and the image obtained consists of a matrix of points each of which corresponds to one of these cells.
  • the light intensity associated with a point of the image depends on the quantity of particles received by the corresponding cell, this quantity being itself dependent on the thickness and the nature of the material of which the object is made. solid angle defined by the source on the one hand and by the cell in question on the other.
  • the wavy path T1 represents that of a neutral particle, a neutron for example, which, after having been emitted by the source 1 and passed through the object 2, the cover 4b of the detector, the grid 7 and the plane of wires 6, reaches a cell 9c of the converter 5.
  • cell 9c made of an adequate material, emits in a statistically observable and reproducible way a fast electron whose trajectory is represented in T2.
  • this fast electron causes the ionization of the gas on its path, and the electrons thus produced drift towards the nearest wire, for example 6c, of the network 6 under the effect of the electric field resulting from the difference between the potentials of the converter 5 and of the wire plane 6.
  • This movement is identified by the arrows such as T3 in FIG. 3.
  • this amplification corresponds to a mode of operation in which avalanches of electrons appear whose size is self-regulated.
  • the corresponding positive ions representing a number of charges equal to that of the charges of all the electrons created, move away from the wire 6c from which they are repelled because of their charge, and drift towards the nearest cathodes, constituted by the grid 7 on the one hand and by the converter 5 on the other hand.
  • the converter 5 has a layered structure supported by an insulating plate 8, the latter being for example formed by a printed circuit board made of epoxy resin, with a thickness of 3.2 millimeters.
  • This plate is covered with a layer of copper 10, a few microns thick.
  • a layer of conductive adhesive 11 On the copper layer 10 is deposited a layer of conductive adhesive 11, with which the assembly can be covered with a layer of a conversion material 12, for example a sheet of gadolinium, with a thickness of tenth of a micron, previously gilded to avoid oxidation.
  • a conversion material 12 for example a sheet of gadolinium, with a thickness of tenth of a micron, previously gilded to avoid oxidation.
  • This stack of layers 10, 11, and 12, deposited on at least the major part of the surface of the plate 8, is then cut, by saw cutter lines such as 13 attacking the upper face of this plate, into elements. electrically isolated from each other, which constitute cells 9a, 9b, 9c, etc.
  • the insulating plate 8 comprises, for each cell such as 9c, a passage such as 14c putting this cell in electrical contact with a conductor such as 15c ending on the other face of the plate 8.
  • each wire such as 6c is stretched exactly over a row of cells such as 9c, these advantageously having a rectangular or square shape.
  • the cathode grid 7 may consist of stainless steel wires with a diameter of 50 microns each, intersecting at right angles, in a pitch of 500 microns, the role of this grid being to allow a symmetrization of the electric field on the wires such as 6c.
  • the plane of wires 6 is produced in the form of a weaving on an insulating frame of golden tungsten wires with a minimum diameter of at least 20 microns, and preferably from 50 to 100 microns each, arranged parallel to one another. others following a pitch S of 2.54 millimeters for example. All of the wires are connected to a source of electrical potential outside the enclosure 3, delivering a voltage of 5000 volts for example.
  • the distance G between the plane of wires 6 and the converter 5 on the one hand and the distance between the plane of wires 6 and the grid 7 on the other hand are preferably equal and of the order of 3 to 5 millimeters.
  • the cells such as 9c for example have the shape of squares of 2 millimeters on a side, produced at the same pace as the wires, 2.54 millimeters in this case.
  • the conversion material 12 used in cells such as 9c advantageously consists of gadolinium in the case where the neutral particles emitted by the source 1 are thermal neutrons, and of iron or silver in the case where these particles are rays X, in particular soft X.
  • the conductors such as 15c are on the one hand connected to the earth potential via respective capacitors such as 16c, on the other hand connected, each at least for a given time interval, to an electronic device 17, of the type known per se, the function of which is to convert the signal present on each of these conductors to a point in a video image and / or to information capable of being stored in an optical, electronic or other memory.
  • the wires such as 6c play the role of means for amplification and collection of negative charges, while the converter and its cells play both the role of conversion means, of cathode, and of means of collection of positive charges.
  • the useful signal for each point of the image of the object, is constituted by the electrical signal present on the conductors such as 15c, the cells such as 9c constitute more precisely the useful elements of the means of charge collection.
  • the invention develops all its advantages when the number of neutral particles detected is less than 105 particles per second and per square centimeter of surface of the converter, and it is of particular interest when the particles detected are thermal neutrons.
  • the charge amplification operation includes the application of an electric field of sufficient value to allow the appearance of electron avalanches of self-regulated size (streamer mode), and it is advantageous , for this purpose, that the ratio of the distance S (FIG. 3) between two neighboring anode wires 6b, 6c, to the distance G between these wires and the cathode 12, is at least equal to 1.
  • this mode allows the creation, for each fast electron emitted by the converter, of an extremely high number of charges, typically of the order of 107 to 109, so that it is possible, even from a small number of particles received by the converter, or a small number of particles converted by it, to obtain an image of an irradiated object such as 2 ( Figure 1).
  • This property is also best exploited according to the embodiment of the invention which comprises an accumulation, for a certain time, of the collected electrical charges, in a capacity such as 16c.
  • this operating mode makes it possible to overcome an intrinsic defect which the solid converters exhibit under certain conditions of use, in particular for the detection of thermal neutrons.
  • the fast electrons from the solid converter have a very high energy dispersion.
  • the number of first ionization charges directly created per unit of distance by a fast electron passing through the gas is a rapidly variable function of the energy of this fast electron, so that the charge collecting elements, the cells such as 9c in this case, risk providing respective signals representative no longer of the number of neutral particles that these elements have received, but of the energy of the fast electrons to which these particles have led by conversion.
  • the "streamer" mode which has the property of amplifying charges in a highly non-linear manner, makes it possible to re-establish this defect by giving rise, for each fast electron, to a number of charges collected which is substantially independent of the number of charges of first ionization directly created by fast electrons.
  • the use of this operating mode thus makes it possible to reduce the fluctuations of the useful signal to a level close to the fish fluctuations of the source.

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  • Physics & Mathematics (AREA)
  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • High Energy & Nuclear Physics (AREA)
  • Materials Engineering (AREA)
  • Measurement Of Radiation (AREA)
  • Analysing Materials By The Use Of Radiation (AREA)

Claims (14)

  1. Vorrichtung zur Erfassung und Lokalisierung von Teilchen in einem Strom neutraler Teilchen, die von einer Quelle (1) emittiert werden, enthaltend:
    - einen im wesentlichen ebenen Feststoffwandler (5), der geeignet ist, beim Auftreffen dieser neutralen Teilchen elektrische Ladungen zu erzeugen, wobei dieser Wandler Umwandlungselemente (9a, 9b, 9c) enthält, die voneinander elektrisch unabhängig sind;
    - Anodendrähte (6a, 6b), die dazu bestimmt sind, auf ein elektrisches Potential gebracht zu werden, das von demjenigen des Wandlers verschieden ist, damit ein elektrisches Feld erscheint, und eine durch das elektrische Feld stimulierte Verstärkung der Ladungen durch Ionisation eines umgebenden Gases zu verursachen;
    - Mittel (9c, 15c) zum Auffangen der Ladungen, die leitende Elemente enthalten, die voneinander elektrisch unabhängig sind und von denen wenigstens einige Umwandlungselemente bilden; und
    - ein Gehäuse (4a, 4b), das für die neutralen Teilchen durchlässig ist und den Wandler, die Anodendrähte, die Mittel zum Auffangen der Ladungen und das Gas umschließt;
    dadurch gekennzeichnet, daß die Umwandlungselezuente, die auch zum Auffangen von Ladungen geeignet sind, durch Zellen gebildet sind, die in einer ebenen zweidimensionalen Matrix verteilt sind, die bezüglich der Quelle jenseits der Anodendrähte angeordnet ist.
  2. Vorrichtung nach Anspruch 1, dadurch gekennzeichnet, daß der Wandler eine isolierende Platte (8) enthält, deren eine Seite die Zellen trägt, wobei diese Platte für jede Zelle eine Durchführung (14c) aufweist, die diese Zelle in elektrischen Kontakt mit einem Leiter (15c) bringt, der zur anderen Seite der Platte geführt ist.
  3. Vorrichtung nach einem der vorhergehenden Ansprüche, dadurch gekennzeichnet, daß die Anodendrähte in wenigstens einer Ebene (6) angeordnet sind, die im wesentlichen parallel zu der Ebene des Wandlers liegt, und daß sie im wesentlichen parallel zueinander liegen.
  4. Vorrichtung nach einem der vorhergehenden Ansprüche, dadurch gekennzeichnet, daß die Zellen ein Umwandlungsmaterial enthalten, das aus der Gruppe gewählt ist, die Gadolinium, Bor und Lithium umfaßt.
  5. Vorrichtung nach einem der vorhergehenden Ansprüche, dadurch gekennzeichnet, daß die Zellen ein Umwandlungsmaterial enthalten, das aus der Gruppe gewählt ist, die Eisen und Silber umfaßt.
  6. Vorrichtung nach einem der vorhergehenden Ansprüche in Verbindung mit dem Anspruch 3, dadurch gekennzeichnet, daß das Gas eine Löschsubstanz enthält, die in einem Anteil von wenigstens 25 % vorhanden ist, und daß das Verhältnis des Abstandes (S) zwischen zwei benachbarten Anodendrähten (6b, 6c) zu dem Abstand (G) zwischen diesen Drähten und dem Wandler (5) wenigstens gleich 1 ist.
  7. Vorrichtung nach Anspruch 6, dadurch gekennzeichnet, daß wenigstens eines der Elemente zum Auffangen von Ladungen mit einem elektrischen Bezugspotential über eine Kapazität (16c) verbunden ist, die geeignet ist, die von diesem Element aufgefangenen Ladungen zu sammeln.
  8. Vorrichtung nach einem der vorhergehenden Ansprüche, dadurch gekennzeichnet, daß sie eine Spannungsquelle enthält, die geeignet ist, zwischen der Kathode und den Anodendrähten eine elektrische Spannung von wenigstens 2000 Volt zu erzeugen.
  9. Vorrichtung nach einem der vorhergehenden Ansprüche, dadurch gekennzeichnet, daß der kleinste Durchmesser der Anodendrähte (6a, 6b, 6c) größer als 20 µm ist.
  10. Verfahren zum Erfassen und Lokalisieren von Teilchen in einem Strom neutraler Teilchen, die von einer Quelle (1) emittiert werden, in einer Vorrichtung nach einem der vorhergehenden Ansprüche, das die Verfahrensschritte enthält, die darin bestehen, daß
    - diese Teilchen auf einem im wesentlichen ebenen Feststoffwandler (5) empfangen werden und somit elektrische Ladungen aufgrund dieser neutralen Teilchen erzeugt werden;
    - diese Ladungen durch stimulierte Ionisation eines umgebenden Gases verstärkt werden; und
    - auf dem Wandler an verschiedenen, voneinander im Abstand liegenden Stellen die Ladungen aufgefangen werden, die in wenigstens einer im wesentlichen parallel zum Wandler liegenden Ebene vorhanden sind;
    dadurch gekennzeichnet, daß die Stellen eine ebene zweidimensionale Matrix bilden.
  11. Verfahren nach Anspruch 10, dadurch gekennzeichnet, daß der Verfahrensschritt der Verstärkung der Ladungen das Anlegen eines elektrischen Feldes umfaßt, dessen Wert ausreichend groß ist, um das Auftreten von Elektronenlawinen mit selbstgeregelter Größe zu ermöglichen.
  12. Verfahren nach Anspruch 10 oder 11, dadurch gekennzeichnet, daß es ferner einen Verfahrensschritt enthält, der darin besteht, daß die aufgefangenen elektrischen Ladungen während einer bestimmten Zeit gesammelt werden.
  13. Verfahren nach einem der Ansprüche 10 bis 12, dadurch gekennzeichnet, daß die Umwandlung der Teilchen in elektrische Ladungen mit einem solchen Umwandlungsgrad erfolgt, daß die Anzahl von erfaßten Teilchen kleiner als 10⁵ Teilchen pro Sekunde und pro Quadratzentimeter der Oberfläche des Wandlers ist.
  14. Verfahren nach einem der Ansprüche 10 bis 13, dadurch gekennzeichnet, daß die neutralen Teilchen im wesentlichen thermische Neutronen enthalten.
EP89912456A 1988-10-28 1989-10-24 Verfahren und vorrichtung zur bidimensionalen lokalisierung nichtgeladener partikel, insbesondere bei geringer zählrate Expired - Lifetime EP0441853B1 (de)

Applications Claiming Priority (5)

Application Number Priority Date Filing Date Title
FR8814187 1988-10-28
FR8814187A FR2638567B1 (fr) 1988-10-28 1988-10-28 Procede et dispositif de localisation bidimensionnelle de particules neutres
FR8814186 1988-10-28
FR8814186A FR2638536B1 (fr) 1988-10-28 1988-10-28 Procede et dispositif de localisation de particules neutres pour faibles taux de comptage
PCT/FR1989/000553 WO1990004851A1 (fr) 1988-10-28 1989-10-24 Procede et dispositif de localisation bidimensionnelle de particules neutres, notamment pour faibles taux de comptage

Publications (2)

Publication Number Publication Date
EP0441853A1 EP0441853A1 (de) 1991-08-21
EP0441853B1 true EP0441853B1 (de) 1994-10-12

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EP89912456A Expired - Lifetime EP0441853B1 (de) 1988-10-28 1989-10-24 Verfahren und vorrichtung zur bidimensionalen lokalisierung nichtgeladener partikel, insbesondere bei geringer zählrate

Country Status (5)

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US (1) US5087821A (de)
EP (1) EP0441853B1 (de)
AT (1) ATE112891T1 (de)
DE (1) DE68918871T2 (de)
WO (1) WO1990004851A1 (de)

Families Citing this family (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6037597A (en) * 1997-02-18 2000-03-14 Neutech Systems, Inc. Non-destructive detection systems and methods
US7377356B2 (en) * 2004-05-25 2008-05-27 Ford Global Technologies, Llc Driver selectable steering ratios
CN102687040B (zh) * 2009-11-18 2015-04-29 圣戈本陶瓷及塑料股份有限公司 用于电离辐射检测的系统和方法
US8319175B2 (en) 2010-08-31 2012-11-27 Schlumberger Technology Corporation Nano-tips based gas ionization chamber for neutron detection
CN104345333B (zh) * 2013-08-07 2017-02-22 清华大学 用于组合中子探测管的阵列组合装置和中子探测设备

Family Cites Families (3)

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Publication number Priority date Publication date Assignee Title
GB1583571A (en) * 1977-06-24 1981-01-28 Exxon Research Engineering Co Hydrocarbon synthesis from co and h2 with ru ni or rh supported on a titanium oxide
FR2591036A1 (fr) * 1985-12-04 1987-06-05 Balteau Dispositif de detection et de localisation de particules neutres, et applications
GB8606086D0 (en) * 1986-03-12 1986-04-16 Marsden P K Cathode/converter

Also Published As

Publication number Publication date
US5087821A (en) 1992-02-11
DE68918871T2 (de) 1995-04-27
WO1990004851A1 (fr) 1990-05-03
EP0441853A1 (de) 1991-08-21
ATE112891T1 (de) 1994-10-15
DE68918871D1 (de) 1994-11-17

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