EP0968519A2 - Chambre d'ionisation pour instruments de mesure radiometriques - Google Patents

Chambre d'ionisation pour instruments de mesure radiometriques

Info

Publication number
EP0968519A2
EP0968519A2 EP98925415A EP98925415A EP0968519A2 EP 0968519 A2 EP0968519 A2 EP 0968519A2 EP 98925415 A EP98925415 A EP 98925415A EP 98925415 A EP98925415 A EP 98925415A EP 0968519 A2 EP0968519 A2 EP 0968519A2
Authority
EP
European Patent Office
Prior art keywords
ionization chamber
chamber according
housing
connections
insulator
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.)
Granted
Application number
EP98925415A
Other languages
German (de)
English (en)
Other versions
EP0968519B1 (fr
Inventor
Siegfried Laube
Franz-Josef Urban
Steffen Hildebrandt
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.)
Vacutec Messtechnik GmbH
Original Assignee
Vacutec Messtechnik GmbH
Priority date (The priority date 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 date listed.)
Filing date
Publication date
Priority claimed from DE1997131608 external-priority patent/DE19731608C1/de
Application filed by Vacutec Messtechnik GmbH filed Critical Vacutec Messtechnik GmbH
Publication of EP0968519A2 publication Critical patent/EP0968519A2/fr
Application granted granted Critical
Publication of EP0968519B1 publication Critical patent/EP0968519B1/fr
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

Links

Classifications

    • 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

Definitions

  • the invention relates to an ionization chamber for radiometric measuring devices, in particular for traversing surface mass measuring systems, consisting of a housing in which filling gas is located, with at least one radiation entrance window and a number of collecting electrodes in the housing with electrical connections which are guided to the outside in an isolated manner, with between the housing and there is an electrical potential difference (voltage) to the collecting electrodes.
  • ionization chambers are usually used as detectors during their production or processing.
  • the ionization chambers consist of a housing, a collecting electrode and a filling gas.
  • the radiation entering through a radiation entrance window generates free charge carriers (ions and electrons) in the filling gas.
  • a voltage applied between the electrode and the housing creates an electric field in the chamber, which the charge carriers follow.
  • the resulting current between the electrode and the housing (in the ⁇ A to pA range) is measured and converted, for example, into voltage signals.
  • the measuring signal is conducted in a highly insulated manner against the housing from the inside of the chamber via a gas-tight bushing with a connection to a signal line to the outside.
  • a ring electrode which acts as a protective ring, is placed around the connection in the insulation layer of the bushing.
  • This protective ring prevents the voltage between the housing and the electrode from dropping directly over a continuous insulation section, as shown in FIG. 1 as the state of the art for an axially symmetrical ionization chamber.
  • the protective ring thus prevents the occurrence of disturbing residual currents, so that the basic current of an ionization chamber without radiation at its working voltage (usually a few hundred volts) is minimal, ie typically less than 0.1 pA is.
  • the radiometric measuring system in a production or processing plant consists of a source of ionizing radiation, the detector, i.e. the ionization chamber and the sample.
  • the degree of interaction between the radiation and the material to be measured e.g. absorption, backscattering, fluorescence
  • the system of radiation source and detector can in most cases be moved across the material web.
  • the basis weight measurement technology opens up new possibilities for solving previously unresolved measuring tasks.
  • the additional information thus created provides a basis for more effective and precise control of production processes.
  • the cross-profile spatial resolution can be refined.
  • the spatial resolution of a cross-profile measurement with the usual axially symmetrical ionization chambers is naturally limited by the chamber diameter.
  • the resolvable structure is specified in the technical literature with twice the detector extension.
  • a finer spatial resolution must be achieved with detectors of smaller dimensions in the transverse direction to the material web. These can be arranged so that a cross-section can be measured with a higher resolution than with a corresponding single detector.
  • the energy spectrum can be used as a result of the interaction of X-rays with the material to be measured.
  • the atomic number of the substrate differs only slightly from the atomic number of the layer to be applied (e.g. zinc on steel). In this case, the known beta backscattering method is unsuitable.
  • Any X-ray fluorescence radiation from the two-component system provides information about the thickness of the applied layer. The energy of the fluorescence radiation is element-specific; their intensity depends on the amount of material examined and thus on the layer thickness.
  • Selective filters absorb e.g. through the K-edge effect strong the X-ray radiation emanating from the layer and largely transmit the radiation emanating from the substrate. Two detector sections with different filters can then be used via calibrations to measure a component of the two-component system.
  • detector sections can be arranged in a multiple chamber as described.
  • n-1 components of an n-component system with a chamber with n measuring sections can be determined in certain cases.
  • This object on which the invention is based is achieved in an ionization chamber of the type mentioned at the outset in that the interior of the housing is divided into a plurality of adjacent and mutually delimited measuring sections with the respective collecting electrodes, and that the collecting electrodes are connected to electrical connections which are connected by the Insulator of a gas-tight multiple leadthrough are led outwards and that the insulator is provided with an electrically conductive area which surrounds the electrical connections and which is arranged electrically insulated from both the housing and the connections, but in the currentless state is at electrode potential .
  • This solution according to the invention enables a basis weight measurement which, for example, achieves a finer spatial resolution or an energy selection of the radiation emanating from the measurement site than the use of conventional ionization chambers.
  • the area surrounding the connections is preferably designed as a protective ring in the form of a metal ring which simultaneously surrounds a plurality of collecting electrode connections.
  • the insulator located between the housing and the protective ring can be part of an insulating tube, the metal contact of which is connected to the housing in a gas-tight manner.
  • a multiple bushing can be connected gas-tight with the opposite metal contact of the insulating tube.
  • the protective ring can also be designed as a surface electrode which surrounds the connections on at least one side of the insulator.
  • the surface electrode is preferably arranged both on the inside of the housing and on the outside of the housing. Both surface electrodes are electrically connected to each other and together with a contact pin and are therefore at the protective ring potential.
  • the measuring sections are delimited from one another by partition walls which extend directly to the radiation entrance window belonging to the corresponding section in order to rule out mutual influencing of the measuring sections, for example by drifting of charge carriers.
  • the collecting electrodes cannot be held mechanically by the signal lines themselves, as is usually the case in conventional single chambers. Instead, they are applied and fixed insulated on a carrier within the chamber, which is at the protective ring potential and is in turn insulated from the chamber housing, which leads to the protection of the protective ring principle.
  • the electrodes can be shaped differently depending on the requirements. So the electrodes can consist of a stretched film or foil strips, or consist of several stretched wires.
  • the ionization chamber has a rectangular or square cross section, the measuring sections being arranged next to one another or in two or more rows flush or offset from one another.
  • the ionization chamber has a round cross section.
  • the measuring sections are arranged radially next to one another in the ionization chamber, it also being possible in principle is to arrange the measuring sections in the ionization chamber concentrically to one another.
  • the individual measuring sections are exposed to differently filtered radiation.
  • the radiation entry windows are partially covered in the case of measurement sections which are offset in several rows in such a way that the seamless, unambiguous measurement of a cross-section section is made possible.
  • 2 shows the structure of an ionization chamber according to the invention with electrodes in the form of tensioned wires; 2a shows a two-row staggered arrangement of measuring sections;
  • FIG. 4 shows a front view of an electrode according to FIG. I; 5 shows a multiple bushing for the connections of the electrodes with an insulator arranged on an insulating tube and a metal ring; 6 a, b a multiple leadthrough with a surface electrode as a protective ring; 7 shows an ionization chamber for the detection of X-rays and a plurality of filters; and
  • FIG 8 shows an ionization chamber with a reinforced one Radiation entry window.
  • Figure 2 shows the structure of an ionization chamber 1 with measuring sections 2 inside the housing 3, which each form independent measuring units.
  • Each section 2 is separated from its neighboring sections by partitions 4.
  • the partitions 4 ensure that oblique radiation is minimized by the chamber volume in the neighboring section, which is achieved in that the partitions 4 extend directly to the radiation entry window 5, which forms the upper end of the housing 3.
  • the ionization chamber 1 can, for example, have a rectangular cross section, wherein the measuring sections 2 can also be arranged in two or more rows offset from one another (FIG. 2a).
  • An electrode 6 is arranged within each measuring section 2 and is adapted to the design of the measuring section 2.
  • Their shape takes account of the demand for the lowest possible gas displacement, the largest possible electrical field, the avoidance of gas amplification and the lowest possible microphony. Therefore, the thickness and the mass of the electrode components are kept small, but the minimum radii are not undercut.
  • the electrode 6 consists either of a holding body 7, on which tensioned wires 8 are arranged, the holding body 7 being arranged in a free-standing manner via an insulating body 21 on a carrier 9 (FIGS. 2, 4). As shown in FIG. 3, the electrode 6 can also have the form of a wire electrode 10 composed of a plurality of wires joined together.
  • the carrier 9 is at protective ring potential.
  • filling gases with high density are preferably used in order to achieve the highest possible radiation absorption near the radiation entry window 5 of the ionization chamber 1.
  • a multiple feedthrough with protective ring is used.
  • This multiple implementation consists of an insulating tube 11, on which an insulator 13 is fastened via a metal ring 12, which serves as a protective ring (FIG. 5). Connections 14 in the form of metal pins are guided through the insulator 13 and are connected to the electrodes 6 via signal lines 15.
  • FIG. 6 shows such a multiple feedthrough with a plurality of connections 14 in an insulator 17 made of a highly insulating material.
  • rings in the form of surface electrodes 18 are applied on both sides around the connections 14, the potential of which acts as a protective ring.
  • the protective ring potential is conducted inwards via one of the connections 14. With this arrangement, only surface currents on the insulation material between the housing and the collecting electrodes are prevented.
  • An ionization chamber 1 with a plurality of sections 2 as described above can also be used in particular for the detection of X-ray radiation in such a way that individual measuring sections 2 are exposed to differently filtered radiation. This is done by arranging 2 filters 20 between the material to be measured 19 and the individual measuring sections.
  • the radiation emanating from a radiation source 22 obtains its characteristic energy spectrum in front of the filter 20 the absorption or fluorescence behavior of the material to be measured 19.
  • a material composed of several components for example paper with fillers, metal alloys
  • FIG. 8 finally shows an ionization chamber with a reinforced radiation entrance window 5, on the outside of which a wire 16 extends, which is fastened, for example, by a welded connection.

Landscapes

  • Measurement Of Radiation (AREA)
  • Electron Tubes For Measurement (AREA)

Abstract

L'invention concerne une chambre d'ionisation destinée aux instruments radiométriques, notamment aux systèmes de mesure d'unités de surfaces traversants. Cette chambre d'ionisation comprend un boîtier qui contient un gaz de remplissage et est doté au moins d'une fenêtre d'entrée des rayonnements et d'un certain nombre d'électrodes de captage pourvues de liaisons électriques conduisant, en version isolée, vers l'extérieur. Une différence de potentiel électrique (tension) règne entre le boîtier et les électrodes de captage. L'invention a pour objet de créer une chambre d'ionisation destinée aux instruments de mesure radiométriques, notamment aux systèmes de mesure de surfaces traversants, possédant une sensibilité suffisante et fournissant des valeurs habituellement bonnes pour les chambres d'ionisation en termes d'étanchéité au vide, de courant de base et de dépendance de température. Pour ce faire, le boîtier (3) comporte un certain nombre de sections (2) adjacentes, délimitées et subdivisées par les électrodes de captage (6). Les électrodes de captage (6) sont reliées aux connexions électriques (14) qui conduisent vers l'extérieur en traversant l'isolateur (13; 17) d'une traversée multiple étanche au gaz. L'isolateur (13; 17) est doté d'une zone électriquement conductrice enveloppant l'ensemble des connexions électriques (14). Cette zone est électriquement isolée du boîtier (3) et des connexions (14), mais, à l'état sans courant, elle est au potentiel des électrodes.
EP98925415A 1997-03-21 1998-03-20 Chambre d'ionisation pour instruments de mesure radiometriques Expired - Lifetime EP0968519B1 (fr)

Applications Claiming Priority (5)

Application Number Priority Date Filing Date Title
DE19712032 1997-03-21
DE19712032 1997-03-21
DE1997131608 DE19731608C1 (de) 1997-07-23 1997-07-23 Ionisationskammer für radiometrische Meßeinrichtungen
DE19731608 1997-07-23
PCT/DE1998/000818 WO1998043116A2 (fr) 1997-03-21 1998-03-20 Chambre d'ionisation pour instruments de mesure radiometriques

Publications (2)

Publication Number Publication Date
EP0968519A2 true EP0968519A2 (fr) 2000-01-05
EP0968519B1 EP0968519B1 (fr) 2003-05-21

Family

ID=26035124

Family Applications (1)

Application Number Title Priority Date Filing Date
EP98925415A Expired - Lifetime EP0968519B1 (fr) 1997-03-21 1998-03-20 Chambre d'ionisation pour instruments de mesure radiometriques

Country Status (5)

Country Link
US (1) US6278121B1 (fr)
EP (1) EP0968519B1 (fr)
JP (1) JP2002507311A (fr)
DE (1) DE59808464D1 (fr)
WO (1) WO1998043116A2 (fr)

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US7701123B2 (en) * 2005-12-13 2010-04-20 Varian, Inc. Electron source for ionization with leakage current suppression
CN115327603B (zh) * 2022-08-01 2024-10-18 中国原子能科学研究院 一种束流探测极排及束流探测装置

Family Cites Families (11)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE1040707B (de) 1956-11-13 1958-10-09 Siemens Ag Strahlungsmessgeraet in Vergleichsschaltung, vorzugsweise Dickenmessanlage
US3676682A (en) * 1968-10-30 1972-07-11 Fred W Falk Absorbed ionizing radiation measuring device
US3575597A (en) * 1969-04-01 1971-04-20 Nasa A multichannel photoionization chamber for absorption analysis
FR2105649A5 (en) 1970-09-16 1972-04-28 Commissariat Energie Atomique Ionisation chamber detector system - for determination of activity of gamma- or x-ray sources
US3914607A (en) * 1973-12-12 1975-10-21 Industrial Nucleonics Corp Thickness measuring apparatus and method for tire ply and similar materials
DE2747872A1 (de) * 1977-10-26 1979-05-03 Philips Patentverwaltung Strahlennachweisvorrichtung
US4301368A (en) * 1980-01-31 1981-11-17 Hospital Physics Oy Ionizing radiation detector adapted for use with tomography systems
US5010252A (en) * 1983-12-27 1991-04-23 General Electric Company Ionization detector
JPS6273548A (ja) 1985-09-27 1987-04-04 Hamamatsu Photonics Kk 電子増倍管
US4751391A (en) * 1986-12-19 1988-06-14 General Electric Company High resolution X-ray collimator/detector system having reduced sensitivity to leakage radiation
DE19545340C2 (de) 1995-12-05 1998-01-29 Vacutec Mestechnik Gmbh Vorrichtung zur Kontrolle von Flächenmassen

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
See references of WO9843116A2 *

Also Published As

Publication number Publication date
WO1998043116A3 (fr) 1998-12-17
US6278121B1 (en) 2001-08-21
JP2002507311A (ja) 2002-03-05
WO1998043116A2 (fr) 1998-10-01
EP0968519B1 (fr) 2003-05-21
DE59808464D1 (de) 2003-06-26

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